title: Treatment of rinse water from zinc phosphate coating by batch and continuous electrocoagulation processes.
abstract: Treatment of spent final rinse water of zinc phosphating from an automotive assembly plant was investigated in an electrochemical cell equipped with aluminum or iron plate electrodes in a batch mode by electrocoagulation (EC). Effects of the process variables such as pH, current density, electrode material and operating time were explored with respect to phosphate and zinc removal efficiencies, electrical energy and electrode consumptions. The optimum operating conditions for removal of phosphate and zinc were current density of 60.0 A/m(2), pH 5.0 and operating time of 25.0 min with Al electrode and current density of 60.0 A/m(2), pH 3.0 and operating time of 15.0 min with Fe electrode, respectively. The highest phosphate and zinc removal efficiencies at optimum conditions were 97.7% and 97.8% for Fe electrode, and 99.8% and 96.7% for Al electrode. The electrode consumptions increased from 0.01 to 0.35 kg electrode/m(3) for Al electrode and from 0.20 to 0.62 kg electrode/m(3) for Fe electrode with increasing current density from 10.0 to 100.0 A/m(2). The energy consumptions were 0.18-11.29 kWh/m(3) for Al electrode and 0.24-8.47 kWh/m(3) for Fe electrode in the same current density range. Removal efficiencies of phosphate and zinc were found to decrease when flow rate was increased from 50 to 400 mL/min in continuous mode of operation. The morphology and elements present in the sludge was also characterized by using SEM and EDX.
authors.affiliation: Department of Environmental Engineering, Gebze Institute of Technology, 41400 Gebze, Turkey.
authors.forename: M
authors.initials: M
authors.lastname: Kobya
authors.forename: E
authors.initials: E
authors.lastname: Demirbas
authors.forename: A
authors.initials: A
authors.lastname: Dedeli
authors.forename: M T
authors.initials: MT
authors.lastname: Sensoy
mesh_terms: D000465:Algorithms; D000535:Aluminum / Q000737:chemistry; D003365:Costs and Cost Analysis; D004563:Electrochemistry; D004566:Electrodes; D004595:Electroplating; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000191:economics / Q000379:methods*; D014961:X-Ray Diffraction; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D010710:Phosphates; D017967:Zinc Compounds; C043952:zinc phosphate; D000535:Aluminum; D007501:Iron