Abstract

Heavy metals that exists in aqueous waste streams of many industries, such as Optoelectronic Industry, can cause various diseases because they are toxic, nonbiodegradable and accumulate in living organisms. Many drawbacks come from heavy metal removal by conventional methods, such as chemical precipitation, ion exchange, or carbon adsorption because they may be ineffective or cost-expensive. Xanthate was selected to be used in this study due to its high affinity toward heavy metals, its effectiveness for metal removal, easy to prepare, and produce lower sludge. Potassium Ethyl Xanthate (KEX), Insoluble Starch Xanthate (ISX), and Crosslinked starch-grafted Polyacrylamide co-Sodium Xanthate (CSAX) were synthesized in this study to investigate their feasibility to remove and recover the wastewater containing heavy metals, such as Molybdenum (Mo), Copper (Cu), or Zinc (Zn) generated from Optoelectronic Industry. The operating conditions such as pH, Sulfur/metal molar ratio, Sulfur and Nitrogen content, and wastewater characteristic such as foreign anion were also considered.
From this study it is expected that Mo6+, Cu2+, and Zn2+ can be removed effectively by KEX, ISX, and CSAX application. By applying KEX in synthetic mixed metal solution, the best removal efficiency obtained to remove all of the metals ions at pH 1, in Sulfur/metal molar ratio of 1.5 and could reach removal efficiency 99.91, 85.53, and 100 % for Cu2+, Mo6+, and Zn2+, respectively. For ISX, the best condition was at pH 4, in molar ratio of 0.5, and could reach removal efficiency 93.50, 12.62, and 100 % for Cu2+, Mo6+, and Zn2+, respectively. CSAX proved its effectiveness to be applied in acid water, pH 1, that could achieve removal efficiency 99.41, 90.64 , 99.46 % for Cu2+, Mo6+, Zn2+ respectively with S/(Cu+Mo+Zn) molar ratio of 0.5. While for real wastewater, KEX could remove Cu2+ until 98.42 %. Continued by using ISX, Mo6+ could be removed until 97 %. The removal of heavy metals in wastewater depends on pH, dosage and wastewater characteristic. KEX, ISX, and CSAX could be applied in the removal of Cu/Mo/Zn effectively in their optimum condition. The proposed application of sequencing batch reactor possibly could be used to remove all of metal ions to be almost 100 % in the end of treatment. The pattern to remove wastewater contained 500 mg/L concentration of mixed metal ions could be drawn. The first treatment use KEX at pH 4, S/Metals of 0.5 placed in the container to remove Cu2+ about 100%. Further, the filtrate is moved into another container which has ISX in S/Metals molar ratio of 0.5 at pH 2 for second treatment to remove Zn2+ about 100 %. Last stage is by applying CSAX at pH 1, S/Metals of 0.5, so the untreated Mo6+ which is being left in the solution could be removed until 90%.

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