some amines as accelerators for cementation of cu in h so

World Journal of Fish and Marine Sciences 12 (2): 32-46, 2020ISSN 2078-4589© IDOSI Publications, 2020DOI: 10.5829/idosi.wjfms.2020.32.46

Corresponding Author: A.A. El-Saharty, Marine Chemistry Lab, National Institute of Oceanography & Fishers, Egypt.32

Some Amines as Accelerators for Cementationof Cu in H SO on Zinc cylinder+2

2 4

A.A. El-Saharty, A.M. Ahmed, S.E. Badr, N. Salaheldin and L.F.Gado1 2 2 2 1

Marine Chemistry Lab, National Institute of Oceanography & Fishers, Egypt1

Chemistry department, Faculty of Science, Alexandria University, Egypt2

Abstract: The cementation process of Cu ions on Zn electrode in acidified CuSO solution was studied.2+4

The rate of cementation of Cu was determined in absence and in presence of various concentrations of organic2+

additives as amines. The influence of some parameters on the rate of cementation of Cu on zinc cylinder was2+

investigated as well. Our result revealed that the rate of cementation as well as the mass transfer coefficient (k)are enhanced by increasing the initial copper concentration and also increase in the presence of amines by anamount ranging from 15% to 97% depending on theirtypes and concentrations. Moreover, (k) also depends onstirring speed and angular velocity. Taking together these results,it was found that the cementation reactionis first order and the rate of cementation of Cu is diffusion controlled. In addition the energy of activation (E )2+

a

and thermodynamic parameters H*, G* and S* were also discussed and the calculated (E ) values confirmsa

that the cementation process is diffusion controlled.

Key Words: Copper removal Wastewaters Heavy metals Cementation kinetics

INTRODUCTION There are a variety of methods employed for metal

Some experts make a distinction between neutralization with acid or base solution, crystallization,contamination and pollution, contamination is used for solvent extraction, flotation, ion exchange, adsorptionsituations where a substance is present in the onto different adsorbents, reverse osmosis, electro-environment, but not causing any obvious harm, while dialysis, electro-winning, electro-deposition andpollution is reserved for cases where harmful effects is cementation [3]. Mostof these method are expensive or doapparent [1]. not remove the metals at trace levels, which are required

Pollutants are basically have two types; primary for drinking water regulations. The development of anpollutants, which exert harmful effects in the form that economical-general sorbent material is necessary tothey enter the environment and secondary pollutants, remove these pollutants from the environment [2]. one ofwhich are synthesized as a result of chemical processes, the most effective techniques for recovering/removingoften from less harmful precursors, in the environment. toxic and precious metals from industrial wasteAlthough highly toxic substances are responsible for streams is Cementation [4]. Really, Cementation is amany cases of environmental pollution, under some metal-replacement process in which a solution containingcircumstances materials which are normally considered ions of less active metal, e.g. Cu , contact with a moreharmless may cause pollution if they are present in active metal such as zinc. An electrochemical processexcessive quantities or in the wrong place at the wrong spontaneously occurs leading to the reduction of the ionstime and this makes definitions difficult [2]. Heavy metal to its elemental metallic state and oxidation of the neutralpollution is a serious problem of world concern. Actually, atoms to its ionic form [5].the contamination by wastes from electroplatingindustries, mining activities, metal finishing plants and Water Pollution: Cities and industries discharge theirnatural erosion are some of the sources of toxic metals untreated or only partially treated sewage and industrialfound in water, soil and air [1]. wastewaters into neighboring streams and thereby

ions removal, such as chemical precipitations,

+2

World J. Fish & Marine Sci., 12 (2): 32-46, 2020

33

remove waste matter from their own neighborhood.But in doing so, they create intense pollution in streamsand rivers and expose the downstream riparian populationto dangerously unhygienic conditions. With theexpending industries that discharging their wastewater inneighboring streams, the latter get all the more pollutedand become progressively unsuitable as sources ofpotable water. Such streams also become unfit as sourcesof industrial water supply. Very often putrefying solidsare deposited along their channels and sides. Fish life isruined, recreation facilities are restricted i.e. the naturalbiological balance is severely upset and in some casestotally disrupted. The problems are becoming increasinglyserious with higher degrees of industrialization and higherstandards of living [6].

Many metals are of concern because of their toxicproperties and some metals are also essential for survivaland health of animals and humans. In risk assessmentsconcerning toxicity of essential metals, their essentialityshould also be taken into account to avoid too lowintakes. This has not always been done in a proper wayand authorities responsible for protecting the public fromadverse health effects from toxicity have issuedrecommendations that have been partly in conflict withthose issued with an aim of protecting from deficiency.

There is an obvious need for an approach includinga balanced consideration of nutritional as well astoxicological data for these metals. These new principlesof evaluation take into account some basic concepts ofinterindividual variability in sensitivity to deficiency andtoxicity. Such variation translated into one interval of(low) daily intake, at which there is a risk of developingdeficiency and another interval of (high) dietary intake, atwhich toxicity may occur.

Copper, derived from the Latin cuprum, is an elementmember of the transition metals group with an averagemass number of 63.546 g/mol. The major stable isotopesof copper are the63 and 65 with respective abundances of69.17% and 30.83%. Other nine synthetic isotopes ofcopper have been reported with half-lives of less than 62hours. A variety of copper complexes have been identifiedwith oxidation states that range from 0 up to + 4, but thecupric Cu(II) and the cuprous Cu (I) are the most stables.Some other physical properties of the copper metal arelisted in the Table (1) below.

Table (1) shows that, copper metal at ambienttemperature is a solid hard to melt. The maximum copperconcentration in drinking water is 1.3 parts per million(ppm) in order to consider the water safe to drink.The EPA regulated the copper down the action level (AL).

Table 1: Some Copper Metal PropertiesIonic radius 0.73 ÅAtomic radius 1.278 ÅElectro negativity Cu(II)Pauling 2.0Ionization Energy (first) 745.4 kJ/molDensity 8.94 g/mLBoiling Point 2,573°CMelting Point 1,083°C

Table 2: The toxicity of copper salts.Compound Dosage (mg /kg)Copper carbonate 159Copper chloride 140Copper sulphate 30Copper nitrate 940

The uses of heavy metal copper have been extremelysubstantial since the industry revolution began.Although copper has seriously affected theenvironment, the industrial consumption rate hasincreased every year due to its excellence in electricalconductivity. Besides being a good electrical andthermal conductor, copper’s other properties includebeing tough, ductile, easily joined, easy to alloy, nonmagnetic and it also has an attractive color. Copper isused in construction materials, electronic products,jewelry and ornaments, coins and transportationequipment [7]. In fact copper metal is insoluble, thus mostcopper enters to water system in form of copper saltssuch as copper chloride, copper sulphate and coppernitrate; such salts were be used in electroplating industry,engraving and photography. Wastes from rinse tank andfilter clean out also find their way into the sanitary system[8]. Moreover, although Copper ion as a pollutant doesn'taccumulate in the human body, but exposure to massiveamounts of copper can cause illness or even death.Copper ions also are highly toxic for aquatic species whenreleased through it. It can cause damage to a variety offauna, specifically fish and invertebrates. The previousstudies revealed that, copper usually water insolublemetal, but due to corrosion, the copper ionic forms, Cu+

ion and Cu ioncan be existed in water [9]. The toxicity of2+

copper salts has been reviewed [10] and some of thesedata are collected as show in Table (2).

While copper is essential element in most organismsthe range between deficiency and toxicity is low in thosewithout effective barriers to control absorption forexample, algae, fungi and some invertebrates. Fish aresensitive to copper, apparently because their gills don'tprovide an effective barrier against absorption. It isknown that 0.01 to 1.7 ppm copper is the toxic for fish andas little as 0.027 ppm copper can be toxic to aquatic


34

Table 3: Concentration of copper in process waste water.Process Copper concentration (mg/1)Plating washPlating wash 20 -120Brass dip 0-7.9Brass mill rinse 6-FebCopper mill rins 4.4-8.5Metal processing 19-74Brass mill washTube mill 204 - 370Rod and wire mill 74Rolling mill 888Brass mill dichromate pickleTube mill 34Rod and wire mill 13.1Rolling mill 27.4Copper rinse 12.2Brass mill rins 13-74Appliance manufacturingSpent acids 4.5Alkaline wastes 0.6-11.0Typical large plater 0-1.0Rinse water Up to 100(20 av.)Pour plating operations 6.4-88Automobile heater production 24 - 33 (28 av.)Silver plating 3-900(12 av.)Silver bearing 30-590 (135 av.)Acid wastes 3.2-19 (6.1 av.)Alkaline wastesBrass industry 4.0-23Pickling bath wastes 7.0-44Bright dip wastesBusiness machine corporation 2.8-7.8 (4.5 av.)Plating wastes 0.4-2.2 (1.0 av.)Pickling wastes 5.2-41Copper plating rinse water 70(av.)Copper tube mill waste 800(av.)copper wire mill waste

insects. Copper toxicity in cheep and cattle ischaracterized by excessive hepatic stores and hemolysisand hemoglobinuria [11]. The normal serum blood level ofcopper is 120 to 145 ng/1. The liver and bone marrow arethe storage organs for excess copper. Acute poisoningresulting from ingestion of excessive amounts of oralcopper salts, most frequently copper sulphate, mayproduce death. The symptoms are vomiting sometimeswith a green blue colour observed in the vomitus,hematemesis, hypotension, coma and jaundice [12].Few cases of copper intoxication as a result of burntreatment with copper compounds have resulted inhemolyticanemia [13]. On the other hand soluble copperwastes of particular concern because of their high degreeof toxicity to aquatic organisms. The principal sources ofsoluble copper wastes have been identified as follow;

rinse water and drag out from the electroplating industry;aching solution wastes from printed circuit production;spent copper analysis; Copper pickling liquor andwastewater from the textile industry. Table (3) summarizesvalues reported [10] for copper in various industrialprocess wastes.

Aim of the Work: The present work aims to study theinfluence of various parameters including, initial copperions concentration, effect of organic compoundsadditives, temperature and stirring speed on the rate ofcementation of copper. The kinetics of the reaction wasstudied and the atomic absorption is used to measure theconcentration of Cu ions. The morphology of the2+

cemented specimens after experiment is also investigatedusing Scanning Electron Microscope (SEM) and Energydispersive X-ray (EDX). All these results together can besupport this search to obtain the optimal condition forCementation process.

MATERIAL AND METHODS

Analar Sulphouric acid and copper sulphate(CuSO .5H O) supplied by BDH chemicals Ltd were used4 2

in preparation of experimental solution. Analar organiccompounds as methyl amine, dimethyl amine, ethyl amine,diethyl amine, monoethanol amine, diethanol amine,triethanol amine were used also. Fig. (1) show Schematicdiagram of the organic additives.

Experimental Techniques: The apparatus in Fig. (2) isused in recovery of copper ion from the solution whichpermits the rotation of an immersed zinc cylinder in 250 mlglass beaker containing 200 ml of experimental solution.The zinc cylinder used in each run is 7 cm length and 3 cmwidth,the cylinder was rotated in experimental solution bylaboratory stirrer and its angular velocity monitored bymeans of an optical tachometer. The reaction vessel wasset in a constant ± 0.05°C ultra-thermostat. The influenceof various parameters were also investigated to determinetheir effect on the rate of cementation ofcopper.

Kinetic Measurements: Kinetic measurements weredetermined via studying various condition of reactionas follow, blank solution of Cu (100 ppm) andvarious2+

concentration of organic compounds (0.0008, 0.001, 0.002,0.004 and 0.006 mol/l) were prepared to determine therate of cementation of Cu in absence and presence2+

of different concentration of organic compounds.Moreover the rate of reaction was determine with different

Motor

zinc or ironcylinder

CuSO4 orK2Cr2O7 + H2SO4\

solution


35

Fig. 1: Schematic diagram of the organic additives Cementation is one of the most effective and economic

Fig. 2: Schematic diagram of the apparatus. mass boundary layer. The rate of cementation not only

temperatures (25, 30, 35, 40°C) as well as various rotation also depends on the nature of the deposited metal,speed (100, 250,400, 500, 700 rpm)were appliedalso. powdery non coherent deposits may enhance the rate ofFinallythe morphology of cemented specimens after cementation while smooth coherent deposit may inhibitexperiment wasinvestigated using Scanning Electron the rate of cementation. Mechanistic studies ofMicroscope (SEM) and Energy Dispersive X-ray cementation reactions have revealed that cementation is(EDX)where, (SEM) graphs and (EDX) analysis could electrochemical in nature which takes place through asupport the experimental measurements and give more galvanic cell [23-25]. For the present case where Cu ionslight on copper production. are cemented on Zn.

RESULT AND DISCUSSION The galvanic cell is: Zn / CuSO / Cu, the cell reaction:

Cementation of Copper from Solution: Currently, Anode: Zn Zn + 2e E = 0.763V (1)environmental hazards related to the presence of metalions in wastewater have great attentions of researchers Cathode: Cu + 2e Cu E = 0.337V (2)due to their lethal effect to plant as well as to human andanimal. On the other hand, a great work has been done on E is the standard cell potential where:industrial waste streams for two purposes, firstly torecover precious metals such as silver and copper thus E = E +E = 0.763 + 0.337 = 1.1V (3)

conserving them, secondly, to remove toxic metal ionssuch as Hg , Cd , Cu , Cr , Pb , etc, from streams to2+ 2+ 2+ 6+ 2+

overcome their lethal effect on plant, human and animal aswell. Copper is among the most prevalent and valuablemetal which strongly used by industry, so it is present inthe wastewaters of many industries. The primary sourcesof copper in industrial wastewater are metal processpickling baths, printed circuit etching solutions andplating baths. The level of copper ions in wastewater mustnot exceed 1.5 mg/l [14].

Generally, copper and heavy metals that may bepresent in industrial wastewater must be removed forhealthy environment, so various treatment methods canbe employed to remove copper, e.g., solvent extraction,adsorption, electrodeposition, biosorption, chemicalprecipitation, biological decontamination,stabilization/solidification and washing. Really

techniques for recovering toxic and/or valuable metalsfrom industrial waste solution. Cementation is used as ageneral term to describe the process whereby a metal isprecipitated from a solution of its salts by anotherelectropositive metal via spontaneous electrochemicalreduction to its elemental metallic state, with consequentoxidation of a sacrificial metal. The process has beenlargely used in industry for a long time, not only inhydrometallurgy but also in the purification process ofwastewaters [14-22].

The cementation reactions are considered asheterogeneous processes limited by diffusion through the

depends on the prevailing hydrodynamic conditions but

2+

4

2+ -o

2+ -o

o

o o anode o cathode

RT 0.059E° = ln K = log KZF 2

Ins

C Ak tC V


36

The standard free energy ( G°) of the cell reaction:

Zn + Cu = Zn + Cu (4)2+ 2+

Is given by

G° = -RtlnK (5)

where K is the equilibrium constant of the reaction.

K = [Zn ] / [Cu ]2+ 2+

Since,

G° = ZFE°

Therefore,

(6)

The equilibrium constant of the reaction (K) = 1.94 x 1037

The high value of the equilibrium constant Kshows that cementation of Cu by Zn can decrease Cu2+ 2+

concentration in waste solution below the maximumpermissible value.

Factors Affecting the Reaction: The removal of heavymetals especially Cu by cementation has been studied2+

by a number of researchers who used different less noblemetals such as Zn, Fe and Al and different methods toenhance the rate of cementation such as the rotating disc[26-27], the rotating cylinder [28], agitated vessels [29],gas sparring [30]. Fixed and fluidized beds [31] andsurface pulsation [32] in most of the cases of thecementation reactions from dilute solutions have beenfound to follow first-order diffusion controlled kinetics[33]. In the present study the effect of different factors onthe mass transfer coefficient for the blank solution as wellas in the presence of organic compounds throughcementation process of copper had been studied asfollow:

Effect of Initial Concentration of Cu Ions: It is clear that,2+

the rate of cementation increases with increasesconcentration of Cu ion, i.e. the cementation rate2+

increase in the direction of precipitation of copper.This may be attributed to the fact that, as the initialconcentration of noble metal in solution (Cu ) increase,2+

the deposited copper tends to pass from fine grained

Table 4: The values of mass transfer coefficient for different concentration ofCu at different temperatures and different rotation speeds2+

Temp. Speed (rpm) Cu conc. (mg/l) kx10 (cm sec )2+ 4 1

25°C 250 50 0.6375 1.45100 4.ta2

30°C 250 50 1.5275 2.02100 5.05

35°C 250 50 1.9075 2.65100 6.32

40°C 250 50 2.5075 2.97100 7.58

25°C 100 100 1.90250 4.42400 8.72500 9.35700 11.43

compact and barely porous structure to a coarse - grainedporous structure which increase the roughness leading toan increases in the rate of mass transfer. The continuedremoval of copper ion with time indicates that thedeposited copper layer is porous and allows copper ionto diffuse through it to react with zinc. The masstransfer coefficient was calculated by the followingequation [14, 33].

(7)

where V is the solution volume; (C ) and (C) are initials o

concentration of Cu and the concentration (mg/l) at any2+

time t; A is the active area of the zinc cylinder (cm ); t is2

the time of reaction (sec). Fig. (3) shows the relationbetween ln (C /C) and time for blank solution at differento

concentrations which gives a straight line pass with originwhich indicates that the reaction is first order. The masstransfer coefficient (k) was also obtained from the slope ofthe above relation (Eq. 7) and thevalues of (k) for differentconcentration of Cu at different temperatures and2+

different rotation speeds wererecorded and plotted asshow in Table (4) and Fig (4).

The results mentioned above revealed that the rate ofcementation increases with increasing initial Cu2+

concentration due to transfer of copper ions from the bulksolution to the zinc surface during cementation process,these may be as a result of (1) diffusion across thediffusion layer ( ) present at the zinc surface and (2)electrostatic attraction (electrical migration) between thepositively charged copper ions and negatively charged

o

o

k k% acceleration = x 100k


37

Fig. 3: The relation between ln (C /C) and time for different Cu concentrationsolutions at 250 rpm and at 25°C.o2+

Fig. 4: Effect of rotation speed on mass transfer coefficient for 100 mg/l Cu concentration at 25°C.2+

zinc anode of the galvanic cell: Zn/electrolyte/Cu compounds can enhance the cementation process.through which cementation takes place. In fact it is well According to the obtained results from the reduction ofknown that both the rate of diffusion and the rate of Cu on surface of zinc cylinder, some conclusions can betransferred ions by electrical migration increase with summarize as the following:increasing reactants bulk concentration [34] which The rate of cementation increased by increasing thelead to a consequent increase in the mass transfer concentrations of the organic compoundadditives.coefficient. In addition when the initial Cu concentration The percentage acceleration for different2+

increases the porous of copper deposits grow rapidly concentrations of the studied additives is estimatedlead to a consequent increasing in the cathode area at 25°C as shown in Table (5). The percentage ofand as reported in the previous studies the reaction acceleration is represented as following:rate is controlled by the cathodic process [35], thusthe rate of cementation as well as the mass transfercoefficient should increase as the initial Cu (8)2+

concentration increases.

Effect of Organic Compounds: Cementation of copper is k = Mass transfer coefficient for blank solution.a commercially important. Its application falls into k = Mass transfer coefficient in presence of organicdecorative, removal of toxic copper ions and so on. compounds.Generally copper is cemented in absence and presence oforganic additives as methyl amine, ethyl amine, diethyl The percentage acceleration increases by an amountamine, monoethanol amine, diethanol amine and triethanol -15.71 to 154.04 depends on the type andamine. The effect of adding organic compounds on concentration of the additives.cementation reaction was investigated which Inspection of Figures (5) shows that the percentagedifferentconcentrations of organic compounds were be acceleration of the studied compounds decreases inused and the variation of ln C /C with time (t) the following order: triethanol amine >diethanol0

wasrecorded. Theseresults confirm thatas the amine> diethyl amine >monoethanol amine > ethylconcentration of organic compounds increases the rate of amine > methyl amine.cementation reaction also increasesi.e.; amines The acceleration of rate of reaction is due to:

2+

where:o


38

Table 5: The percentage acceleration of cementation reaction of (100 mg/l Cu solution) containing different concentrations of organic compounds at 25°C2+

and at250 rpm

Methyl amine Ethyl amine Diethyl amine Mono ethanol amineConc. X 10 (mol/l) -------------------------------------------------------------- % acceleration -----------------------------------------------------------------------3

0.8 -15.71 20.00 21.89 -1.171.0 -1.43 38.57 46.60 15.302.0 30.00 50.00 66.37 31.784.0 38.57 57.14 92.72 64.726.0 48.57 67.14 104.25 97.66

Fig. 5: The relation between (% acceleration) and concentration of different organic compounds for 100 mg/l Cu2+

solution at 250 rpm and 25°C.

It may be form complex with Zn and reaction takes k = A exp (- E /RT) (10)2+

place forward.

Zn + Cu Zn + Cu exponential factor, E is the activation energy, R is the2+ 2+

Amine ions can operate as ion prior phase transfer ofmetal present as complex ion [36]. ln k =-E /RT + ln A (11)

Effect of Temperature: Cementation of copper by zinc in Table (7) summarized the data of ln k and1/T, whenlnpresence of organic compounds at various temperature k was plotted against 1/T a straight line was obtained as298, 303, 308 and 313°K was studied and the relation showing in Fig. (6) where, the slope is equal(- E /R) whilebetween ln C /C and time for Cu at different temperatures (ln A) [37] is the intercept, thus, the activation energy "E "0

2+

was investigated which lead to obtain the mass transfer could be calculated from graphs and their values werecoefficient values atdifferent temperatures as shown in tabulated as shown in Table (8) which confirm that theTable (6). It can be seen that the cementation rate reaction is diffusion controlled [38].increases as the temperatureincreases.In addition as animportant parameter for determining the rate controlling Thermodynamic Treatment of the Reaction: The valuesstep, the activation energy E for a given cementation for the enthalpy of activation H*, entropy of activationa

reaction was calculated using Arrhenius equation as S* and free energy of activation G* can be obtainedfollow: by using the following equations:

a

where k is the mass transfer coefficient, A is a pre-a

general gas constant and T is the absolute temperature.

a

a

a


39

Table 6: The values of mass transfer coefficient k x 10 (cm sec ) for 100 mg/l Cu solution in presence of different concentrations of organic compounds at4 1 2+

different temperatures and at 250 rpmMethylBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

Amine conc.(mol/l) Temp. --------------------------------------------------------------- k x 10 (cm sec ) --------------------------------------------------------------4 1

25°C 4.42 3.73 4.36 5.75 6.13 6.5730°C 5.05 5.81 6.06 6.44 6.95 7.5235°C 6.32 6.89 8.09 8.46 8.91 10.0440°C 7.58 8.21 9.35 10.11 10.23 11.31

Ethyl amineBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) Temp. --------------------------------------------------------------- k x 10 (cm sec )--------------------------------------------------------------4 1

25°C 4.42 5.31 6.13 6.63 6.95 7.3930°C 5.05 6.77 7.11 7.51 8.26 8.6635°C 6.32 7.65 8.59 8.93 10.96 11.7140°C 7.58 10.01 12.59 12.99 13.47 14.41

Diethyl amineBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3


25°C 4.42 6.13 6.48 7.36 8.52 9.0330°C 5.05 7.40 7.94 9.83 10.27 10.3435°C 6.32 7.93 9.84 10.26 11.90 12.9640°C 7.58 12.31 12.60 13.33 13.77 15.08

Monoethanol amineBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3


25°C 4.42 4.87 5.10 5.83 7.28 8.7430°C 5.05 5.83 7.28 8.74 9.47 10.9335°C 6.32 7.36 8.74 9.47 11.87 12.0940°C 7.58 8.08 9.76 11.70 13.80 15.30

Diethanol amineBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3


25°C 4.42 4.74 5.41 7.44 8.46 8.9330°C 5.05 7.44 8.80 10.15 11.50 12.8635°C 6.32 8.12 9.47 10.83 12.86 13.5340°C 7.58 9.47 10.83 12.86 13.53 15.30

Triethanol amineBlank 0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3


25°C 4.42 6.83 8.12 8.80 9.00 9.2030°C 5.05 10.76 11.03 11.23 11.77 12.0435°C 6.32 11.58 11.87 12.09 12.67 12.9640°C 7.58 10.56 12.40 13.10 13.98 16.39

Table 7: The relation between ln (kx10 ) and (1000/T) for 100 mg/l Cu solution in presence of different concentration of organic compounds at 250 rpm and4 2+

different temperatureMethylamine0.8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.11 0.26 0.54 0.60 0.673.30 0.55 0.59 0.65 0.73 0.813.25 0.72 0.88 0.93 0.98 1.103.19 0.90 1.03 1.10 1.11 1.22


40

Table 7: ContinuedEthylamine0.8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.46 0.60 0.68 0.73 0.793.30 0.70 0.75 0.81 0.90 0.953.25 0.82 0.94 0.98 1.18 1.253.19 1.09 1.32 1.35 1.39 1.46

Diethyl amine0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.47 0.66 0.79 0.93 0.993.30 0.51 0.86 1.08 1.12 1.133.25 0.86 1.08 1.12 1.27 1.353.19 1.30 1.32 1.38 1.41 1.50

Monoethanol amine0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.26 0.42 0.55 0.77 0.963.30 0.55 0.77 0.96 1.04 1.183.25 0.79 0.96 1.04 1.26 1.283.19 0.88 1.07 1.25 1.41 1.52

Diethanol amine0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.35 0.48 0.80 0.96 1.043.30 0.80 0.96 1.11 1.23 1.343.25 0.88 1.04 1.17 1.34 1.393.19 1.04 1.17 1.34 1.39 1.52

Triethanol amine0. 8x10 1.0x10 2.0x10 4.0x10 6.0x103 3 3 3 3

conc.(mol/l) (1000/T) ---------------------------------------------------------------------- 8+ln (k) --------------------------------------------------------------------3.36 0.71 0.88 0.96 1.19 1.213.30 1.17 1.19 1.21 1.26 1.283.25 1.24 1.26 1.28 1.33 1.353.19 1.15 1.31 1.36 1.43 1.59

Table 8: The values of activation energy (E kJ /mol) for 100 mg/l Cu solution in presence of different concentrations of organic compoundsa2+

Blank Methyl amine Ethyl amine Diethyl amine Monoethanol amine Diethanol amine Triethanol amineConc. X 10 (mol / l) ------------------------------------------------------------------------- E (kJ /mol) -------------------------------------------------------------------3

a

0.8 28.55 39.5 31.4 33.4 32.4 29.6 21.91.0 40.1 36.4 34.2 25.3 24.1 17.62.0 30.4 33.9 28.3 21.9 12.4 184.0 27.6 35.3 24.7 17.4 17 12.46.0 29.6 35.7 27.4 27.7 22 18.9

H* = E - RT (12) Effect of Stirring on the Rate of Cementation: The effecta

S*/R =ln A - ln ( Te/ h) (13) process was invested using a series of experiments.

G* = H* - T S* (14) 100,250,400,500 and 700 rpm in presence and absent of

where is the Boltzmann’s constant, (e = 2.7183) and h is of rotational speed on the mass transfer coefficient (k)Plank's constant (143). could be used also to determinewhether, a cementation

The activation energy the free energy G* enthalpy process is diffusion or chemically controlled, where if theH* and entropy S* of activation were calculated mass transfer coefficient increase with increasing stirring

theoretically from equations. It is noticed also that all the speed, this confirms that the reaction is diffusionvalues of S* are highly negative values indicating a controlled, while if k is independent of stirring speed, themore ordered systems and non-random distribution of reaction is chemically controlled. Fig. (7) and Fig. (8) showions on the zinc cylinder. the relation between Ln (C /C) and time at 25°C and

of stirring speed on the reaction rate of cementation

Various stirring speeds were used as follow

1x10 mole /l of different organic compounds. The effect3

o


41


42

Fig. 6: Typical plot of ln( k ) and(1000/T) for 100 mg/l Cu solution in presence of different concentration of organic2+

compounds; a) methyl amine, b) ethyl amine, c) diethyl amine amine, d) monoethanol amine, e) diethanol amine,f) triethanol amine and at 250rpm and at different temperatures.

Fig. 7: The relation between Ln (C /C) and time for 100 (mg/l) Cu solutionat 25°C and different rpm.o2+

Fig. 8: The relation between Ln (Co/C) and time for 100 (mg/l) Cu2+ solution in presence of 1x 10 mol/l of organic3

compounds "methylamine" 25°C and different


43

Table 9: Effect of rotation speed (rpm) on the mass transfer coefficient (k x10 ) ( cm sec ) for 100 mg/l Cu solution contain 1x 10 mol/l of the organic4 1 2+ 3

compounds at 25°C2-bromo aniline Methyl amine Ethyl amine Diethyl amine Monoethanol amine Diethanol amine Triethanol amine

Speed (rpm) µ -------------------------------------------------------------------------- (k x10 ) ( cm sec ) ---------------------------------------------------------------0.7 4 1

100 5.18 2.10 3.35 2.91 3.64 2.11 2.91 3.64250 9.83 4.55 4.36 6.13 6.48 5.10 5.41 8.12400 13.66 7.06 7.06 7.28 7.28 5.83 7.28 9.47500 15.97 10.93 9.76 10.93 11.58 7.28 9.47 10.93700 20.22 13.84 13.84 12.75 15.51 10.93 15.30 15.30

Fig. 9: The relation between k x 10 (cm.sec ) and for 100 mg/l Cu solution at 25°C and different rpm in presence4 1 0.7 2+

of 1X10 mol/l of organic compounds: a) 2-bromoaniline,b) methylamine, c) ethylamine, d) diethylamine, e)3

monoethanol amine, f) diethanol amine and g) triethanol amine.

different rpm of zinc cylinder for 100 (mg/l) Cu solution transfer coefficient value (k x10 ) revealed that as the2+

in absence and in presence of 1x 10 mol/l of rotation speed increases the value of (k x10 )3

methylamine as additives. In addition Table (9) gives increases i.e. a cementation process is diffusionthe effect of rotation speed (rpm) on the mass controlled. On the other hand Table (9) also showstransfer coefficient (k x10 ) (cm sec ) for 100 mg/l Cu that the mass transfer coefficient increases as4 1 2+

solution contain 1x 10 mol/l of various organic angular velocity increases, this may be due to the3

compounds at 25°C. These changes in the mass following effects:

4

4

0 5 10 15 20Energy(keV)

0

100

200

300

Cps

Zn Cu

Zn

Zn

65.2%

17.2%8.3 % 9.3%

100 ppm Cu2+(a)

0 5 10 15 20Energy(keV)

0

100

200

300Cps

Z nCu

Zn

Zn

71.4%

6 %15 %

7.6%

(b) 100 ppm Cu2+ +1 x 10-3

mol. /l diethanol amine

0 5 10 15 20Energy (keV)

0

100

200

300Cps

ZnCu

Zn

Zn5 %

15 %

72.2 %

7.8 %

(c)


44

Fig. 10: SEM morphology of zinc a) before cementation b) after cementation at initial copper concentration 100 mg/l,time = 60 min and 250 rpm.

The higher the angular velocity, the higher thesolution flow and the thinner the diffusion layer;which lead to a higher rate of transfer of copper ionsto the zinc surface and, at the same time, the rate ofcementation was enhanced due to the porousdeposit layer which formed on the zinc cylinder.The rate of cementation will increase as the rotatingspeed increases due to the contact of copper ionswith zinc cylinder increases per unit time.

The angular velocity is given by: = 2 rpm /60 (15)

Fig. (9) gives the relation between the mass transfercoefficient k (cm sec ) and the angular velocity in1 0.7

presence of different organic compounds at 25°C. Straightlines were obtained where the rate of cementationincreases as rotation increases, thus the obtained resultsconfirm that the cementation is diffusion controlledprocess.

Scanning Electron Microscopic (SEM): ScanningElectron Microscopy (SEM) was used to examine themorphology of the cemented copper. Fig. (10a & b),show the examination of the electrode surface beforeand after cementation which revealed a significantchanges and confirmed the change in the Zn sheetsurface as a consequence of the cementation process.These experiments were proceeded for 100 mg/l of copperion concentrationthrough 60 min at 25°C and 250 rpm.The deposit of copper after cementation processseems to be dendritic with a high porosity in clustershaped with numerous holes as shown in (Fig. 10b) whichhave been created by the corrosion of the zinc.Accordingly, the increase in the copper cementation rateis strongly due to the morphology changes of deposit.The rate enhancement can be resulted either from changes Fig. 11: EDX profile analysis for zinc rod immersed in thein deposit structure which increases the reactive surface solution containing Cu2+ in absence andarea, or increases roughness of the deposit. presence of amines (a-c).


45

Application of EDX Spectroscopy: Energy dispersive 7. Harris, D., 2002. Quantitative Chemical Analysis, 6X-ray (EDX) was used to study our results. From the ed.; W.H. Freeman and Company: N.Y, 2002.Fig. (11) (a-c) show the analysis of blank solution which 8. EPA. Management of Scrap Tires, www.epa.gov/indicate that the composition of cemented copper garbage/ tires /index.htm (accessed June 2007).precipitate was (16.2 % pure Cu) and 66.1 % pure zinc 9. Dickinson, D., 1974. Practical Wastewater Treatmentwhich indicated that the precipitate is pours. due to the and Disposal, applied Science", Publishers Ltd.,use of zinc cylinder and high degree of porosity which London, 1974.allow the appearance of zinc. In presence of amines the 10. Marshal Sitting, 1976. Toxic Metals Pollution Controlamount of copper cemented increases from compound and Worker Protection".Noyes Data Corporation,(17.3%) diethanol amine to (19.5%) triethanol amine these New Jersey, U.S.A, 1976.indicated that the rate of cementation enhances in 11. Casorelt, L.J. and M.D. John Doull, 1973. Toxicologypresence of amines which agree with our results. the Basic Science of Poisons, Macmillon Publishing

CONCLSION 12. Chuttani, H.K., P. Gupti and S. Gultali, 1965. Am. J.

The cementation process of Cu ions on Zn anode in 13. Manzler, A.D and A. Schreiner, 1970. Ann.Intrn.2+

CuSO solution was studiedand the obtained results Med. J., 73: 409.4

revealed that the rate of cementation and the mass 14. Ponder, S.M., J.G. Darab and T.E. Mallouk, 2000.transfer coefficient increase as the initial Cu Environ. Sci. Technol., 34: 2564.2+

concentration increases and they also depend on the type 15. Alowitz, M.J. and M.M. Scherer, 2002. Environ. Sci.and concentration of amine, temperature, stirring speed Technol., 36: 299.and the angular velocity. The overall mass transfer 16. Jung, R.S. and R.C. Shiau, 2000. J. Membrane Sci.,coefficient valuesconfirm that the cementation reaction is 165: 159.first order and the rate of cementation of Cu is diffusion 17. Huck, R.A. and J. Amer, 1972. Leather Chem.Assn.,2+

controlled as well as cementation is electrochemical in 57: 422.nature which takes place through a galvanic cell, which is 18. Parker, H.W., 1975. Wastewater System Engineeringin accordance with our previous studies. Moreover, the “New Delhi”, 1975.activation energy E values also prove that the reaction is 19. Yamauchi, T. and T. Nakamura, 1975. Jpn. Kokai,a

diffusion controlled. 69: 544.

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2. British Medical Association, 1991. Hazardous waste Usoara, 33: 466.and Human Health, Oxford University Press, Oxford, 24. Basha, C.A, A.W. Shi and D.Y. Yu Hianbao, 1986.1991. Electrochem. Soc., 5: 23.

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some amines as accelerators for cementation of cu in h so

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