The 10 th International PSU Engineering Conference May 14-15, 2012 Biosorption of Zn(II) and Pb(II) by activated sludge Chayapat Hassapak* 1 , Sininart Chongkhong 1 , Pakamas Chetpattananondh 1 and Tanit Chalermyanont 2 1 Department of Chemical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112 2 Department of Civil Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112 E-mail: Abstract The industrial waste water that is contaminated with zinc(II) and lead(II) ions, heavy metals, must be passed into a treatment process before leaving , into a public water source. The waste water having heavy metals can be treated by several ways. A conventional method that has still been widely used is an adsorption. Importantly, bioabsorbents were alternative absorbent materials, that are interested because of their availability and low cost. The activated sludge, a bioabsorbent, is waste by-product from wastewater treatment system. The removal of Zn(II) and Pb(II) ions from aqueous medium by activated sludge was examined. Biosorption experiments on the effect of initial pH of solution were optimized out at the desired pH value using the activated sludge. They were carried out in 50 ml capacity of centrifuge tubes shaken at 170 rpm at 30°C in a water bath and for experiments on the effect of contact time were carried out in 250 ml capacity of Erlenmeyer flask in the same condition as above. The removal using activated sludge of Zn(II) ion and Pb(II) ion was studied as a function of 1-12 hr contact time and 4-9 initial pH. From the result were found that the %removal of Zn(II) and Pb(II) were increased with pH from 4 to 6 and remained constant up to pH 9 and the biosorption equilibrium time was established after about 11 hr. Keywords: Adsorption; Activated sludge; Heavy metal 1. Introduction The discharge of heavy metals into public river and canal has become a matter of concern in many countries. These pollutants are introduced into the ecosystem as a result of industrial operations, for example; mining and smelting of metalliferous ores, electroplating, gas exhaust, energy and fuel productions, fertilizer and pesticide applications, and generation of municipal waste.[1] The majority of heavy metal contaminants are commonly: Cd, Cr, Cu, Hg, Pb, and Zn [2]. In a few years, the removal of the heavy metals in aqueous solutions that has been used are chemical precipitation, solvent extraction, reverse osmosis, ion exchange, evaporation, fixation/solidification, filtration, adsorption, oxidation, reduction, dialysis/electro-dialysis, etc. The adsorption method is one of the famous techniques that are employed widely. Examples of its advantage were easy to usability, inexpensive and effective for low metal concentration. There are many absorbents that are used for the metal removal for instance activated carbon, zeolite, carbon nano-tube, bioabsorbents[3]. The new technologies involving the removal of heavy metals from waste waters has directed attention to biosorption, based on types and capacities of various biological materials. Biosorption can be defined as the ability of biological materials to accumulate heavy metals out from waste water through metabolical media or physico-chemical pathways of uptake. The major advantages of biosorption over conventional treatment methods are low cost, high efficiency, and using the industrial waste as well [4]. In this study, the absorbent, that is collected, is activated sludge. Because the activated sludge have related with many researchs that study about biosorption of heavy metals by activated sludge [5-7]. 2. Experimental materials and methods 2.1. Chemicals Deionized water (DI-water) was used to prepare all solutions. Stock solution of metal used in this study was prepared by dissolving the desired quantity of Zinc Chloride (ZnCl 2 ) for Zn(II) and Lead(II) chloride (PbCl 2 ) for Pb(II) in DI-water. All pH adjustments were made by using Nitric acid (HNO 3 ) and Sodium hydroxide (NaOH). 2.2. The adsorbent The raw activated sludge was collected from frozen food industry in Hat Yai, Songkhla, Thailand. The activated sludge was dried in an oven at 60 °C for 48 h, and finally was crushed and sieved to the size of 1.0-2.0 mm. The adsorbent were stored in desiccator at an ambient temperature. Energy-Dispersive X-Ray Spectroscopy (EDS) can be used to determine the chemical composition of activated sludge that was used in this research, which consists of C, O, Na, Al, Si, P, S, Cl, K, Ca and Fe.