| Landfill leachate is a kind of high concentration of organic wastewater which is generated during the landfill process of municipal solid waste.It has potential negative effects on environment and human health once leaked.Adsorbed by activated carbon,resin or bentonite is an effective method of leachate treatment because of the good adsorption rate and effect.Since high price of the adsorbents,easy to produced secondary pollution and the reproductive issues,it is necessary to find a new economic and environmental friendly adsorbent.Biochar is a kind of highly aromatic insoluble solid material which produced by pyrolysis carbonization of plant biomass under hypoxic conditions completely or partially.And it is regarded as a prospect material in the field of agriculture and the environment as the low cost and wild sources.Numerous studies showed that biochar as a sorbent has a good effect on adsorption of various pollutants in wastewater and soil.However,single-component simulated water samples were used in most studies,which are different from mixed waste water in treatment mechanisms.Therefore,it is of great importance to further study the treatment effect of the comprehensive wastewater by biochar.We studied the adsorption mechanisms of COD treated by biochar,and found the best adsorption conditions by combining the single-factor and orthogonal test.Because of the complexity of the composition in landfill leachate,single COD value is difficult to reflect the water quality characteristics.Therefore,the removal efficiency of other contaminants in landfill leachate and the ecotoxicity changes on barley have been studied,under optimum conditions of COD adsorption.The results showed that:1.The adsorption of COD in landfill leachate by biochar were accorded with pseudo-second order adsorption kinetics model and the Langmuir adsorption isotherm,and the adsorption rate was mainly controlled by liquid film diffusion and chemical adsorption reaction.It always showed that the adsorption was a slow process,the adsorption equilibrium was achieved after 36 h.2.The single factor and orthogonal experiment showed that the best adsorption conditions of COD were:carbon raw material dosage 50 g·L-1,temperature 30?,pH 5.5.time 48 h.The major factors affecting adsorption were time,temperature,dosage,pH,respectively.3.When the removal efficiency of COD was maximum,the chroma of landfill leachate was significantly removed,and COD,BOD5,ammonia nitrogen and total salt of leachate had been removed 83.00%,82.55%,26.42%,12.28%,respectively.4.The toxicity effect study of barley showed that:the inhibiting effect on the germination rate,root length,shoot length,fresh weight,dry weight were significantly reduced,while the promoting effect on the generating of chlorophyll was obviously increased and the inhibition of the lipid peroxidation was markedly enhanced after treated with biochar.Taken together,it suggested that biochar can act as a kind of economic and green adsorbent,which has a broad application in dealing with complex sewage. |
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