Preparation Of Biochar By Low Temperature Pyrolysis And Its Performance On Benzene Removal

Benzene is one of the most representative pollutants among volatile organic compounds(VOCs),and its emissions come from many sources,and all industries involving chemical materials have benzene emissions with significant industry characteristics.The World Health Organization has designated benzene as a strong carcinogen because it is highly toxic and can have serious effects on human health and the ecological environment.Therefore,effective removal of benzene is necessary.At present,adsorption method has the advantages of low cost,wide applicability,easy to use,and can be recycled by deactivating the adsorbent,and is considered the most effective method for benzene purification by adsorption,but the performance,cost,and preparation process of the adsorbent used still need to be further optimized to meet the actual needs in industrial production and life.Based on the above problems,this thesis carried out a study to develop low-cost and high-performance benzene adsorbents,to establish a better preparation process for benzene adsorbents,and to provide a certain experimental basis for reducing the preparation cost of adsorbents.The main research contents and conclusions are as follows:(1)Yellow bamboo was selected as the raw material for the preparation of biochar adsorbents by high-temperature cracking and hydrothermal roasting methods,and the effects of pore structure characteristics and surface properties of the adsorbents obtained by the two preparation methods on the benzene adsorption activity were further investigated.The experimental results showed that under the same preparation conditions,the adsorption effect of the adsorbent prepared by hydrothermal roasting was four times higher than that of the adsorbent prepared by high-temperature cracking,and the adsorption capacity of the adsorbent obtained after hydrothermal pretreatment of biomass and then roasting was up to 107.27 mg(benzene)/g sorbent at low temperature of 55 ℃.Due to the formation of carbon microspheres,the adsorbent prepared by hydrothermal roasting method formed more stacked pores while ensuring the microporous structure,so the pore structure was more abundant,which led to the enhancement of the mass transfer of benzene molecules and greatly improved the adsorption performance of the adsorbent on benzene.(2)The adsorption activities of four different active metals,solid-to-liquid ratios,roasting temperatures and nickel nitrate solution concentrations on benzene were investigated by hydrothermal loading and impregnation loading methods.The results showed that compared with the impregnation method,the adsorption performance of the active metal was better because it was highly dispersed on the biochar carrier by the hydrothermal loading method.The best adsorption activity of benzene was obtained when the active metal was Ni for the preparation of adsorbent,the solid-to-liquid ratio was 60,the roasting temperature was 850 °C,and the concentration of nickel nitrate ranged from 0.02 to 0.1 mol/L.(3)In order to further obtain a cost-effective adsorbent,copper-containing wastewater was used as a source of active metals in the adsorbent,thus reducing the adsorption cost and providing a new idea for the deep treatment of heavy metal wastewater.By regulating the concentration of copper ions in copper-containing wastewater and the preparation conditions,the surface modulation of activated carbon using hydrothermal loading method not only successfully extracted copper ions from copper-containing wastewater as the active metal,but also successfully achieved the standard discharge of copper-containing wastewater.