The Study Of Waste Sludge Bleaching With Electrochemical Chlorine-containing Bleaching Technology

As an eco-friendly technology, electrochemical method has plenty of significant advantages, such as lower energy consumption, more environmental compatibility, versatility, simple in treatment process, lower medicaments, etc. Nowadays, there has been the most interest in the use of electrochemical method in the field of environmental engineering practice, and there are more and more researches on the electrochemical chlorine-containing bleaching technology. however, few in bleaching-waste sludge are studied by this method. Due to the thoughts of the resources-recycling and energy consumption-reducing, the aim of achieving the utilization of pollutant, the paper proposed a electrochemical chlorine-containing bleaching technology based on the flow-through operation mode.The study analyzed in this mode, the operating mechanism of electrochemical ion-exchanging reactor, and approved the feasibility of chlorine-containing bleaching method through analyzing the effects of current density, electrolysis times, concentration of NaCl on the electrogenerated active chlorine.The results of electrochemical chlorine-containing bleaching showed that in this operation mode, electrogenerated active chlorine was feasible for waste sludge bleaching. The current density, the electrolysis times and the concentration of NaCl could be the major factors on the effects of the whiteness of waste sludge and the current efficiency. On the basis of the single factor experiment, the conclusion of the response surface optimization experiment model for one-stage electrochemical bleaching was as follows:in the condition of current density lOmA/cm2, concentration of NaCl2.5%, electrolysis times3.45h, pH9-11, room temperature, the whiteness of waste sludge could be bleached from16.87to39.84, and the verifying test results revealed that the model was feasible. In the same processing condition, the whiteness of waste sludge increased to41.28, and the bleaching time could be reduced by45min with the method of "cathode-anode" two-stage bleaching.The result of scanning electronic microscope (SEM) showed that the waste sludge bleached by the treatment process of "cathode-anode" two-stage bleaching, was better into layer structure. The result of thermogravimetric analysis (TGA) showed that the waste sludge was lower in both moisture content and volatile, and also approved that the organics in waste sludge could be reduced effectively with this electrochemical chlorine-containing bleaching technology.The study also investigated the broad application of electrochemical chlorine-containing bleaching technology, which was used for bleaching the kaolin. The results showed that the particle size was smaller through bleached by different bleaching processes in this mode, and the whiteness and field were respectively60.48and65.76%. The result of scanning electronic microscope (SEM) showed that the particle size bleached by anode water was smaller than that by other bleaching processes, and the particle layered structure respectively bleached by "cathode water-anode water" and anode water was better.