| With industrial development, China's most industrial areas have suffered drinking water source of organic micro-pollution. In particular the persistent organic pollutants pose a threat to the basin's environment, people's health and sustainable economic development. PCBs are a class of representative persistent organic pollutants. Research shows that PCBs have been widely used in electric power, chemicals, plastics processing, printing and other areas. As a result, such substances widely present in the water environment, as a threat to human health. Based on PCBs pollution, the standards for drinking water quality require the total PCBs less than 0.5μg/L. But the conventional water treatment processes are bad at removing PCBs.In this research, powdered activated carbon was used to remove trace amounts of PCBs in water. PAC surface properties have been analyzed. PAC adsorption kinetics and isotherms of PCBs were conducted with Allocation of water. PAC adsorption efficiency of PCBs was compared on the allocation of water and natural water. It was studied that the effect of NOM on the apparent solubility of PCBs, as well as, the effect of NOM on the Adsorption. The effect of pH, temperature and ionic strength on PCBs adsorption onto PAC was studied.Results showed that apparent solubilities of PCB52 and PCB153 were 31.59μg / L and 3.06μg / L, if the HA concentration was 4.59mg / L. Compared with solubility in pure water, there was an increase of 10% and 236%. Among the four PAC A, B, C, D, PAC A contained the most functional groups. The amount of carboxyl groups, basic groups, lactones groups and phenolic hydroxyl groups were respectively 4.75 mmol/g,5.25 mmol/g,5.3 mmol/g and 0.01 mmol/g. The zero charge points were 7.94, 9.48, 9.84 and 9.66. Four kinds of PAC had surface area of 1470 m~2/g, 592m~2/g, 956 m~2/g and 431 m~2/g, respectively. Micro pore surface area of PAC A was largest. Particle size of four PAC in the water was mainly 10μm below. If initial concentration of PCB153 was 3μg/L, the rate of adsorption of PCB153 on PAC in water would be so rapid that the adsorption capacities were made use of more than 56%(PAC A) and 82%(PAC D) at the time of 5min respectively,and 90%(PAC A)and 97%(PAC D) in 30min. The adsorption process tended to reach equilibrium in 2 hours. The experimental adsorption data showed good correlation with pseudo- second-order kinetics equation. The adsorption isotherm can be fitted well with Freundlich model. PAC had a large adsorption capacity of PCBs when the pH value of water approached the isoelectric point. The adsorption of PCBs on PAC was an endothermic process. High temperature can be conducive to the adsorption capacity of PAC. High ionic strength could weaken PAC adsorption capacity. NOM existed in water had a negative influence on the adsorption kinetic and amount of PCBs on PAC. In the raw water of Songhua River, PAC adsorption of PCBs was still in very high efficiency. The pH, NOM, ionic strength and particles of raw water affected the adsorption performance of PAC. Experiments with raw water determined how much PAC requiredfor the different concentrations of PCBs in water. If the conventional process can not compliance, adding PAC to the original water can effectively remove the PCBs. |
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