Study on characteristics of catalyzed internal electrolysis treating simulated rural lead pollution water

Abstract: Lead may cause a series of health problems which ranged from behavioral problems, learning disabilities to seizures or even death. The conventional treatment methods adopted for removing lead from wastewater included chemical precipitation, electro-chemical reduction, ion exchange process and adsorption method. However, these methods had certain disadvantages, such as high cost, technical sophistication, generation of sludge, or other waste products that needed to be processed. Therefore, it was necessary to research and develop a treatment method which had the advantage of relative high efficiency and low operating cost. On the basis of above considerations, an emerging lead removal system, namely, the catalyzed internal electrolysis based on advanced ferric-carbon filler, was applied to treat lead-containing wastewater, especially the lead pollution water in rural areas. To investigate the effect of catalyzed internal electrolysis based on advanced ferric-carbon filler treating water that simulated lead pollution in rural area, this study adopted single factor experimental design and orthogonal experimental design that included eight factors and three levels, making study on initial pH(1.0~8.0), reaction time(10-90 min) and aeration quantity(0-12 L/h). The results showed that the removal rate of Pb2+ rose slowly at first and then dropped sharply when pH value rose from1.0 to 8.0. The removal rate of Pb2+ rose steadily when the reaction time increased from 10 min to 60 min and tended to be stable when the reaction time kept extending to 90 min. The removal rate of Pb2+ rose sharply at first and then dropped slowly when aeration quantity increased from 0 to 12 L/h. The influence of the three factors on removal efficiency of Pb2+were as follows: aeration quantity>initial pH value>reaction time, the best reaction condition occurred when the initial pH value was at 3.0, the reaction time was 60 min and aeration quantity was 6L/h. This paper fitted the reaction stage according to the first-order kinetic model, observed the surface feature and structure changes of the ferric-carbon filler before and after the reaction by using scanning electron microscope (SEM) and analyzed the components of solution after the reaction by using X-ray diffraction (XRD) and inferred that the mechanism for catalyzed internal electrolysis removing lead was oxidation-reduction and chemical precipitation. In optimum experimental conditions, the concentration of Pb2+ could fall to 0.037 mg/L after treatment when initial Pb2+ concentration was 1.0 mg/L, which could meet the requirement on limiting value of the case-Ⅲ water specified in Environment Quality Standards for Surface Water (GB3838-2002). This research results may provide theoretical foundation and design basis for the remediation of the lead pollution water in rural areas.