| In this paper, five kinds of powdered activated carbons (PACs) and five organic matters were chosen as adsorbents and target organic polutants, and the adsorption equilibriums and adsorption kinetics of the target organic polutants on five PACs in nature water were studied respectively. The adsorption characteristics of natrual organic matter (NOM) on PACs were analyzed using high performance size exclusion chromatography (HPSEC). The relationship between the physical and chemical properties of PAC and the adsorption properties of organic polutants in nature water was investigated. Besides, the competitive adsorption of NOM with the target organic polutants was discussed, and the competitive adsorption mechanism between NOM and the target organic polutants was studied based on the physical and chemical fractionation of NOM. Last, from a case study of PAC adsorption technique in an emergency, the relationship between the initial concentration of organic matter, the dose of PAC, the adsorption time and the adsorption removal efficiency was determined using static test, and the removal efficiencies of pollutants on PACs under different initial concentrations were studied in the case of admissible adsorption contact time and PAC dose in water treatment plant. Several important conclusions were developed as below:(1) Both Langmuir and Freundlich isotherms were fitted well to the adsorption of MP and TCE on five kinds of PACs in nature water, and Langmuir isotherm was better. The adsorption processes were priority adsorptions, and the adsorption amount for MP was higher than that for TCE. The adsorption kinetics of MP and TCE on PACs were well fitted by Pseudo Second-order Equation Model and Homogeneous Surface Diffusion Model (HSDM), and the adsorption kinetics at different PAC doses could be predicted effectively using HSDM by fitting the adsorption kinetics at one PAC dose.(2) The physical property (pore properties) of PAC was the critical factor to determine its adsorption capacity of MP and TCE in natural water. The micropore area of PAC was the critical factor to determine its adsorption capacity of the low molecular weight and low-pole SOC organic pollutants. The adsorption of the NOM with apparent molecular weight (AMW)< 500 on PAC was primarily impacted by the micropore surface area, and that of NOM with 500< AMW< 3000 was mainly affected by the mesopore surface area combined with the mesopore size distribution, while the adsorption capacity of NOM in this range of molecular weight was determined by the area of the mesopore with pore size> 3nm.(3) Because the pore blockage effect of NOM was absent, the surface diffusion coefficient (Ds) obtained from the adsorption of MP on PACs in pure water was similar to the Ds obtained from simultaneous adsorption of MP and NOM in nature water. The Ds of MP on two PACs was independent of PAC dose in simultaneous adsorption in nature water, which just resulted in the change of removal effeciency. When PAC was preloaded with NOM in nature water, the Ds of MP on preloaded PAC was lower than that on fresh PAC, and it decreased with a decrease in PAC dose. Comparing two natural waters, the Ds on preloaded PAC JC in MPS reservoir water was lower than that in MY reservoir water under the same NOM surface concentration.(4) The removal effect of Atrazine and chloroethylene on PAC was not evident. If the concentration of Atrazine and chloroethylene in nature water exceeds that in standard, PAC adsorption should be used by combining with other technologies to remove organic matter, including advanced oxidation, enhanced filtration, etc. The removal effect of parathion on PAC was evident. For the nature water with certain concentration of parathion, the concentration of parathion in the effluent water could come up to the standard only by PAC adsorption under the admissible PAC dose in the pratical application in water plant. |
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