Effects Of Coexist Heavy Metals And PH On Sorption Of PCP On Biofilms In Natural Waters

Organochlorine pesticides and their impact on the environment has always beenone of the hot issues of environmental science, their migration and transformationare still the focus of related academic research. Adsorption is the key point ofcontrolling the pollutants’ migration and transformation about their subsequentaccumulation, degradation and so on. In natural waters, organochlorine pesticides areoften co-existed with other pollutants such as heavy metals, who will make someinfluence on the sorption of organochlorine pesticides. And the environmentcondition such as pH will also affect the sorption result.Natural Biofilm has a verysignificant impacton on the migration and transformation of various types ofpollutants including heavy metals and persistent organic pollutants. This studyobserve the effect of coexisting pollutants and changing pH on the adsorption ofpentachlorophenol by biofilm.In this paper, we simulated natural waters condition in laboratory to do theadsorption experiments, the research is about the effect of Pentachlorophenoladsorbance onto the biofilm, when changing the concentration of copper, chromium,lead and arsenic(coexisted heavy metals) at a fixed pH, and when changing the pHat a certain concentration of heavy metals.Use Langmuir, Freundrich and Linear models to fits the experimental data ofadsorption, Langmuir model show better results of fitting the results, its correlationcoefficients are all better than0.96. In the fixed pH system, all the four heavy metalsdecreased the sorption of pentachlorophenol on biofilms and the degree of decreasewas enhanced with the increasing concentration ratio of heavy metals topentachlorophenol. copper was the most significant to decrease the sorption amongthese metals, which reduced the pentachlorophenol sorption amount by53.5%. Thesecond was chromium, lead and arsenic has less impact on the adsorption inhibition.Results of Boehm titration inferred that the sorption inhibition could be caused bythe competition of heavy metals with pentachlorophenol on the sorption sites inbiofilms. In the Fixed concentration of heavy metals and changing pH experiment, results show that the sorption inhibition was enhanced in acid conditions, whereas itwas weakened in base conditions. This is because combining abilities of heavymetals and pentachlorophenol with biofilms, and the compositions of biofilm aredifferent under the conditions of different pH values.