Efficiency And Mechanism Of Pentachlorophenol Removal From Water By The Combined Process Of Ultrafiltration And Nano-size PAC

Pentachlorophenol (PCP) is a kind of toxic organic pollutant, and also a kind of broadspectrum pesticide. Some effective removal methods are necessary when PCP leak intodrinking water. The research mainly studied the characteristics and mechanism of PCPremoval from water by the combined process (NPAC-UF) of ultrafiltration (UF) andnano-size powdered activated carbon (NPAC) appearing recently.In the paper, the characteristics of PCP removal from water were first investigated byNPAC and PAC with different materials. We studied comparatively the adsorption efficiencyof PCP by oak PAC (20nm,60nm,200nm,2.0μm) and Chinese fir PAC (80nm,200nm,2.0μm,5.0μm). It is found that the absorption laws of PCP absorbed by the two kinds of PACare all accord with Langmuir formula. The second-order kinetics model can greatly describethe adsorption dynamics behavior of the pentachlorophenol on the two kinds of materials. Theadsorption ability of PAC can be greatly reduced with the solution pH rising, but is nearly thesame at pH3~5, which means the polarity and the form of PCP in the solution play animportant role. The smaller size PAC has rapider adsorption rate, larger adsorption capacityand smaller saturated dosage. The Chinese fir PAC including two micron-sized PAC showsstronger absorption ability than the nanoscale oak PAC. The main reason is that the formerhad many microporous structures and had larger surface area and micropore volume. Thisresearch could provide the theoretical guidance for selecting and evaluating the PAC whichadsorbed organic pollutants in water.The bacteriostasis of NPAC was also studied in the research. The results reveal thatNPAC has inhibition to microorganism. The bacteriostasis is better when the NPAC size issmaller, concentration is larger, and contact time between NPAC and microorganism islonger.The performance characteristics of the combined process of NPAC-UF were furtherstudied in this research. During the rejection performance experiments for NPAC by thedifferent ultrafiltration membrane, it is found that1000Da ultrafiltration membrane cancompletely intercept the NPAC. In the rejection experiment using the membrane underdifferent conditions, we discover that the membrane flux will decrease while reducing thestirring intensity and NPAC size and increasing the NPAC concentration, but decreases in all conditions are small. The mechanism is that there are gaps among the cake layer particlesformed by NPAC, which means that a good permeability exists. At the same time, the cakelayer can be removed by the magnetic stirrer disturbance more likely. During the PAC-UFexperiment we found that PCP removal efficiency for combined process is better than theNPAC adsorption and ultrafiltration.The ultrafiltration membrane has the function of a secondintercept.