title: Pretreatment of wastewater from triazine manufacturing by coagulation, electrolysis, and internal microelectrolysis.
abstract: We studied the pretreatment of concentrated wastewater from triazine manufacturing by coagulation, electrolysis, and internal microelectrolysis. Results show that coagulation by polyaluminum chloride at dosage of 0.5 g/L could remove up to 17.2% chemical oxygen demand (COD) from the wastewater. Electrolysis using iron electrode achieved 33.2% COD removal at current of 2A in 180 min, which was attributed to coagulation and oxidation of the organic contaminants in the wastewater by the radicals (OH and O) and oxidants (O2, O3, and H2O2) produced in electrochemical reactions. Internal microelectrolysis using iron chips and granular activated carbon (GAC) showed that up to 60.5% COD could be removed under the conditions of iron/GAC/wastewater volumetric ratio of 3:2:490, sparge ratio (ratio of air flow rate to volume of wastewater) of 2:490 min(-1), and reaction time of 132 h. COD reduction in internal microelectrolysis was attributed to a combination of chemical and physical processes, mainly oxidation by radicals and oxidants formed in electrochemical reactions, adsorption on, co-precipitation with, and enmeshment in ferrous and ferric hydroxides resulted from Fe2+ released during anode oxidation. The results suggest that internal microelectrolysis using iron chips and GAC is a promising, low-cost alternative for pretreating concentrated wastewater from pesticide manufacturing.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA. cheng533@stanford.edu
authors.forename: Hefa
authors.initials: H
authors.lastname: Cheng
authors.forename: Weipu
authors.initials: W
authors.lastname: Xu
authors.forename: Junliang
authors.initials: J
authors.lastname: Liu
authors.forename: Huanjun
authors.initials: H
authors.lastname: Wang
authors.forename: Yanqing
authors.initials: Y
authors.lastname: He
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D004572:Electrolysis; D005427:Flocculation; D006540:Herbicides / Q000737:chemistry*; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D014227:Triazines / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D006540:Herbicides; D007220:Industrial Waste; D014227:Triazines; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; D000536:Aluminum Hydroxide; D002244:Carbon; D007501:Iron