Removal of heavy metals in plating wastewater using carboxylated alginic acid
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Removal of Heavy Metals in Plating Wastewater Using Carboxylated Alginic Acid Choong Jeon, Jae Yeon Park and Young Je Yoo~'
School of Chemical Engineering, Seoul National University, Seoul 15 [-742, Korea (Received 7 Fehruwy 2001 . accepted 4 .hdy 2001)
Abstraet-Potentially, biosorption is an economic process lbr metal sequestering from water. Carboxylated alginic acid showed high uptake capacities tbr heavy metals of 5-6 meq/g dl-y mass, For application to actual plating wastewater, the carboxytated alginic acid was immobilized using PVA, In order m remox, e chelating or organic materials in plating wastewater, oxidation using sodium hyfx~chlorite was pertbrmed as a pretreatment. When earboxylated alginic acid bead was applied in a packed-bed contactor, the breakthn,ugh point of copper ion in the acid-alkaline wastewater appeared around 350 bed volumes; thc breakthrough point of nickel ion in the chelating wastewater emerged around 200 bed volumes. The admrption capaciD' lbr heavy metal of the carboxylated alginic acid bead was highm" than that nfa commercial ion exchanger tlR-120 plus) in plating wastewater. Key ~.ords: Alginic Acid, Plating Waste~ater. Heavy Metal, Biosorption
The alginic acid used in this study was purchased from SigmaAldrich (U.S.A.). The reaction procedure for chemical modification ofalginic acid was as follows. 5 g ofalginic acid was oxidized in 10 mM solution of potassium permanganate at 30~ for 30 rain. Reacted mixture was separated by centf~fugation and washed five times thoroughly with distilled water. After being dried at 60 ~ it was immobilized. The immobilization method has been presented in the literature [Jeonet al, 1998]. All sorption experiments were performed by using immobilized carboxylated alginic acid. Wastewater was obtained fi'om the Panwall plating factor3,'in Ansan, Korea and kept at room tc~nperature before use. Generally, wastewater in the Panwall plating factory is re-collected in three types. This wastewater" is divided as acid-alkaline wastewater, chelating wastewater, and chromic wastewater. 'Ihe pH control and oxidation reaction were used as pretreatment methods for effectively removing heavy metals. Sodium hypochlorite, which is known as a strong oxidation reagent, was purchased from Aldrich Chemical Company, inc. qhe procedure for all the biosorption experiment in batch was as follows. At first, sodium hypochloritc of l0 mM was reacted with wastewater for 1 hr at room temperature. Predetermined carboxylated alginic acid beads were put into a given amount of oxidized wastewater, and then mixed by shaking at 200 rpm in an incubator at 30 ~'C."lq~eplt was adjusted periodically to pi-I 4.0 by adding 1 N NH4OH and I-INO~as required. When the pH of metal solution was maintained as 4,0, the solution was centrifuged at 11,000 a force for 20 min to remove suspending biosorbent, then metal concentration of the suwmatant was analyzed by using AAS (Atomic Absorption spectroscopy: Perkin-Elmer 3f10, USA) or ICP (Inductively Coupled plasma Spectroscopy: Perkin-Elmer ICPS-75
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