INVESTIGATING THE USE OF HEAVY METALCONTAMINATED COCO PEAT ASAN ADDITIVE IN MORTARSAlexis Bryan G. Rivera1, Ma. Doreen E. Candelaria, Jessie O. Samaniego, Maria Antonia N. Tanchuling, Marielle Elaida G. Monteclaro, Ernanie G. Marin1Institue of Civil Engineering, College of Engineering, University of the Philippines-Diliman, agrivera40165@gmail.comReceived Date: October 24, 2014

AbstractCoco peat, a by-product of the extraction of coco fiber from coconut husk, has been proven to be a viable material for sorption of heavy metals. While still being further developed to enhance its efficiency as a biosorbent material, its disposal after contamination has not been given much attention. Thus, this study focuses on the feasibility of using contaminated coco peat as additive in mortars, as one of the means of disposal of contaminated cocopeat. This study uses the concept of solidification and stabilization in immobilizing the heavy metals in a contaminated coco peat that was used as a sorbent material in the treatment of wastewater from the small-scale gold mining site in Paracale, Camarines Norte. The coco peat was added to a mortar mix and replaced a portion of the cement (by mass) in the mixture. The effectiveness of this method could be defined by two parameters: (1) the Unconfined Compressive Strength of the samples and (2) the ability of this method to immobilize the heavy metals which was assessed through Toxicity Characteristic Leaching Procedure (TCLP). The amount of coco peat added in the samples was varied with increments of 10% of the amount of cement in the mix. Using ASTM C270-12a as the standard, results show that only mortars with up to 40% coco peat passed the Type N mortar, which is used for general purpose application and has a minimum average compressive strength of 5.2 MPa. TCLP examination of the mortars showed that concentrations are below detection limit value for As, Ba, Cr, Cd, Pb, Hg, and Se, according to DAO 29.Keywords: Mortars, Coco Peat, Solidification, Stabilization, Biosorbent, Disposal

1. INTRODUCTION

1.1. Background Mining is a growing industry in the Philippines. Gold, copper and nickel are some of the minerals which are richly deposited in the country and are being extracted by small and large scale miners. Mining helps in utilizing the deposited minerals; however, the recovery of these minerals also produces wastewater which can harm the environment. Mining and industrial wastewater is a major source of heavy metal pollution in the environment. Large scale miners have the means of treating wastewater before it is discharged to nearby bodies of water. However, small scale miners cannot afford to install a wastewater treatment plant and therefore they settle with sedimentation tanks.Coco-peat is the by-product of the extraction of coco fiber from coconut husk. It is typically used as a soil additive but it is now being developed as a sorbent material. Heavy metals are adsorbed by being attached or attracted to the surface of the sorbent material making the heavy metal content of the wastewater less than when it was discharged from the mining site. After the heavy metals have been adsorbed, the quality of the water may now be acceptable to be discharged to the nearest body of water. However, the heavy metals were just transferred to another medium (i.e. coco peat) and may still be hazardous to the environment if not disposed of properly. There is a need to immobilize the heavy metal in the sorbent material to keep it from causing harm to the environment. Currently, the means of treating contaminated sorbent materials are by desorption, incineration, and solidification/stabilization.Solidification/stabilization (s/s) is a process that immobilizes heavy metals by the chemical bonding between a contaminant and an additive e.g. Portland cement or pozzolan. Additives are used to transform the waste into a more manageable form, a less toxic form by physically or chemically immobilizing the waste constituent. When the additives react, a high strength waste/concrete matrix is produced, therefore, the waste is contained by entrapment of waste particles (Ballesteros, 1991). Cement-based s/s technology is widely used because it offers assurance of chemical stabilization of many contaminants and produces a stable form of waste (Singh, Pant, 2005).Many studies were made regarding the effectiveness of this method on contaminated inorganic sorbent materials. The present study aims to determine the efficiency of this method on organic sorbent materials or biosorbent materials by adding contaminated coco-peat in a concrete mix.Concrete is one of the most widely used construction materials. On average, more than two tons per year of concrete is produced for a person (Chandler, 2011). It is usually made by mixing gravel, sand, cement and water. The amount of each component used in mixing concrete depends upon the factors considered during the mix proportioning such as type of construction, strength requirement, and where the concrete will be used. Chemical additives or admixtures may be added to the mixture to improve the quality of the concrete, i.e. by modifying the time for the materials to react, reducing heat produced, accelerating strength development at early age, increasing the durability of concrete, etc., in order for the concrete to adapt to the environment where it is mixed and exposed to. Mineral additives are mixed into concrete and replace a portion of the cement. This is done to reduce the amount of cement used making the mix more economical. The additives used may be organic or inorganic, depending on the property of the concrete being improved. In this study, the spent coco peat will be used as an additive in the concrete.Small amounts of some organic compounds can delay the Portland cement-based reactions responsible for solidification which makes it (biosorbents) harder to solidify than inorganic sorbent materials (Ballesteros, 1991). The strength of the concrete with contaminated coco-peat would have to be checked as well to determine its possible structural or construction application.1.2. Statement of the ProblemUtilization of biosorbent materials such as coco peat offers effective and economic alternative in removing heavy metal content of wastewater produced by mining industries, thus providing safe means of wastewater disposal. However, the disposal of used sorbent materials has not been given too much attention. Due to high heavy metal content, used coco peat poses a threat to the environment as it leaches contaminants to the ground. 1.3. ObjectivesThe goal of the study is to assess the effectiveness of using heavy metal contaminated coco peat as additive in concrete as a means of disposal. The study aims to immobilize the heavy metals in the contaminated coco peat using the concept of solidification and stabilization (s/s); furthermore, to give additional value to the product of s/s, the immobilization will be done through mortars and concrete. The study also aims to optimize the concrete mix by determining the maximum amount of coco peat that could be added to the mix without compromising the strength of the concrete.

1.4. Significance of the StudyWaste disposal has always been a problem in this country. Some wastes contain harmful elements or compounds which may pose danger to the people and the environment. It is necessary for some waste to be treated first before it is disposed of to its designated landfill. Using spent coco peat as an additive in concrete will not only help make a concrete mix more economical but it will also provide a safe means of disposal for the heavy metal contaminated organic sorbent.