Photocatalysis And Micro-biological Co-degradation Remove The RoHS Directive Pollutants

Along with society's progress and the development of industry,a large number of electronic products are produced and consumed each year,forming tens of thousands of tons of electronic-waste.According to statistics,China produced 6 million 30 thousand tons of electronic waste in 2014.At the same time,china imports tens of millions of tons of foreign waste,barbaric dismantling industry has brought serious e-waste pollution to our environment.Electronic waste contains more than 700 kinds of substances,mainly composed of metal and non-metallic.RoHS?Restriction of Hazardous Substances?is a mandatory standard enacted by the European Union legislation.The purpose of the standard is to eliminate six kind of substances?Pb?Hg?Cd?Cr6+,PBBs and PBDEs?of the electronic products.According to the properties of these six kinds of pollutants,they can be divided into two categories:heavy metals and persistent organic compounds?POPs?.This study is focused on the removal of these six kinds of pollutants in the electronic waste by photocatalysis and microbial methods.On the basis of preliminary laboratory simulation of pollutants degradation experiment,we use this control method to remove there heavy pollution of soil,surface water and groundwater pollutant in the famous city of electronic waste in China,Guiyu Town,Shantou City,Guangdong Province.This research mainly adopts the following chemical and biological treatment and strengthening method.This paper adopted the method photocatalysis remove the RoHS directive pollutant,mainly to prepare the anodic oxidation of titanium dioxide nanotube array to research the reduction of sedimentary of heavy metal ions and degradation of PBDEs.It also examines the silane coupling agent KH570 respectively modified titanium dioxide nanotube array on reinforcement of removal of pollutants.Photocatalytic method is one of the most popular method of pollutant treatment.Semiconductor catalysts under the effect of photons produce electron transition,and have the oxidation ability of holes and electrons with the reducing power.Pollutant that reduction potential is higher than the conduction band edge position of heavy metal ions such as Cr???,Au,Ag,Hg???,Cu,Fe???can be reductive deposition removal,at the same time,persistent pollutant PBDEs can produce reductive debromination process,and its degradation product is organic matter,such as,the generation of bromine,two coumarone and so on.Because TiO₂ semiconductor catalysts has excellent catalytic ability,relatively stable physical and chemical properties and low-cost source,it is paid a close attention to the processing of environmental pollutants such as heavy metal ions in reductive deposition and degradation of persistent organic pollutants?pops?.However,because of its strong hydrophilic,the present study of titanium dioxide nanometer catalyst in strong hydrophobic organic compounds in the process of the degradation of the actual application effect is not very well.This research adopts the silane coupling agent KH570 side to TiO₂ nanotube array on the surface,which not only improves the ability of the combination of catalysts and pollutants,but also improves the performance of catalyst.on the one hand,because R of silane coupling agent side is part of long chain alkane,which improves the catalyst for the affinity of hydrophobic organic compounds,On the other hand,silane coupling agent which modifies on the surface of the photocatalyst can provide additional hydroxyl as hole trapping agent on the surface of the catalyst activity or consumption point to reduce composite electronic-hole,thus improves the photocatalytic performance.This study also examines the biological leaching and immobilization/stabilization of heavy metal pollution of soil solidification stability research.This research collected one purified individual plant of thiobacillus ferrous oxide from hunan Shui Kou Shan mine acid wastewater to make biological leaching study in the heavy pollution the soil surrounding the zhuzhou smelter,the experimental results show that in the 15 d leaching experiments,in regulating medium with pH value of 2.5,the leaching rate of Cu and Cd can reach more than 99%,while not adjust medium pH value of the system,the leaching rate could reach 85%and 90%,respectively.This study investigates the combined curing of the soil heavy metal pollution of fly ash cement to strengthen the study,by improving the cement-based solidification method to deal with contain high concentrations of Cu,Cd,Pb contaminated soil.Modified material for quality than for 5:5:5:10:0 5-0.75:0.25 of calcium nitrate,sodium nitrite,sodium aluminate,sodium sulfate,sodium lignosulfonate,sodium lauryl sulfate,triethanolamine,and bentonites.Through orthogonal test the best proportion of curing materials as cement,fly ash,bentonite,admixture?cement,fly ash,bentonite,i.e.?weight ratio of 200:300:have,at the same time also shows that the mixed concrete admixture can improve the strength of the solidified body,and the stability of the weight of metal solidification,increase the content of heavy metal residue state for the stable.Another piece of the main work of this study was to the RoHS directive and pollutant removal method,this paper carried out the acidophilic thiobacillus study of soil heavy metal pollution and degradation of PBDEs,experiments show that acidophilic thiobacillus PBDEs no degradation.White rot fungi?WRF?have the ability to bioremove the heavy metal and POPs.The results show that WRF also could make contribution to the degradation of PBDEs.From Hengyang,Hunan province,a kind of fungi which have the high ability to degrade PAHs was screened and acclimated to degrade PBDEs.The result can indicated that the PBDEs are more refractory than PAHs.Other kind of aerobiotic and anaerobic microorganisms,screened from Electronic industrial park of Guiyu town,have the high performance to degrade PBDEs,so that the conclusion was shown that the microorganisms cultured from the serious contaminative area were better than others.After repeatedly domesticate,the degradation rate of aerobiotic microflora was reached to 40%after 14 days and anaerobic microflora was 63%.This study researched the effect of adding carbon source,the enzyme inducers and strengthens the means such as electron acceptor on microbial degradation of PBDEs reinforcement.Experiments showed that glucose is the best carbon source,the 2,4-dichlorophenol is the best inducers in aerobic biodegradation and the yeast extract is the best carbon source,the 2,4-dichlorophenol is the best inducers and NaHCO3 is the best mineral salt in anaerobic biodegradation.