Evaluation Of Performance Of Biochar Adsorption Removal Of Diclofenac Sodium

With the progress of society and the development of the economy,the awareness of protecting the environment has become more and more popular.At the same time,people's awareness of medical treatment and nursing is gradually increasing.The production and usage of Pharmaceuticals and Personal Care Products?PPCPs?have risen sharply.They enter the environment through many ways,such as excretion,direct discharge and medical and nursing wastes,resulting in the gradual increase of their residual concentration in the environment.As a new type of pollutant,PPCPs have been frequently detected in water sources such as rivers,lakes,and other water bodies,which has negatively affected the growth of terrestrial animals and aquatic organisms,and has brought potential risks to human health.Diclofenac sodium?DCF?is a non-steroidal anti-inflammatory drug,which is an important drug component of PPCPs.Diclofenac sodium is difficult to be biodegraded,and the conventional water treatment process can only partially remove it,which is easily harmful to the environment.In this paper,straw,bamboo and wood chips were used as raw materials,and different biochar materials were prepared by different methods at different temperatures.DCF was used as the target pollutant to investigate the adsorption performance of different biochar materials and their prospects in practical applications.The main results are as follows:?1?Preparation and characterization of biochar materialsRice straw was used to prepare straw-biochar?SBC?activated by ammonium hydrogen phosphate.Bamboo biochar?BBC350,BBC700,BBC900?and wood biochar?WBC350,WBC700,WBC900?were obtained by pyrolysis of bamboo and wood chips at 350,700,and 900?,respectively.The surface morphology,pore size distribution and surface oxygen-containing functional groups of different biochar materials were analyzed by means of SEM,BET,FT-IR,Boehm titration and pH_pzc determination.SEM results showed that the surface of straw biochar was rough and uneven with dense pore distribution.The surface of bamboo biochar is flake-like.As the temperature increases,the surface wrinkles gradually deepen.According to BET analysis,the specific surface area of bamboo biochar increases in the order of BBC350,BBC700,BBC900,which is composed of mesoporous and microporous.The surface of wood biochar is honeycomb-like,and with the increase of temperature,the degree of particle breakage is gradually deepened,and the pore structure is becoming more complicated.The BET analysis results showed that the specific surface area increases in the order of WBC350,WBC700,WBC900,which is also composed of mesoporous and microporous.According to the titration results of FT-IR and Boehm,the seven biochar materials all contained lots of surface oxygen-containing functional groups.And the number of surface oxygen-containing functional groups of biochar materials prepared at different temperatures was gradually decreased with increasing temperature.The pH_pzc of SBC,BBC900 and WBC900 was determined by the drift method.And the pH_pzc of SBC,BBC900 and WBC900 was 2.40,2.07 and 2.14,respectively.?2?Effect of pH,anion and other factors on the adsorption processTaking DCF as the target pollutant,the adsorption properties of SBC,BBC900 and WBC900 were studied.The effects of adsorption time,dosage,pH value,anion concentration and other factors on the adsorption process were discussed.The adsorption removal rates of DCF by SBC,BBC900 and WBC900 are continuously decreasing with the increase of pH value.When pH value was 5.00,the removal effect was the best.Coexisting anions had little effect on the adsorption process,and the difference was within 8%.?3?Adsorption kinetics and adsorption thermodynamicsThe theoretical maximum adsorption capacities of SBC,BBC900 and WBC900were 312.5,354.83 and 294.12 mg/g,calculated by Langmuir isotherm modelrespectively.The adsorption processes of DCF by SBC,BBC900 and WBC900 were more consistent with pseudo-second-order kinetics model.The Freundlish isotherm model can better simulate the adsorption process of DCF on SBC.Both Langmuir and Freundlish isotherm models can well simulate the adsorption of DCF on BBC900.Langmuir isotherm adsorption line model can better simulate the adsorption process of DCF on WBC900.Thermodynamic parameters illustrated that the adsorptionprocesses of DCF by SBC,BBC900 and WBC900 are both spontaneous,endothermic and entropy-increasing.?4?Comparison between different biochar materialsThe adsorption removal rates of DCF on BBC350,BBC700 and BBC900 at 24h were 0%,32%and 100%,respectively.The adsorption removal rates of DCF by WBC350,WBC700 and WBC900 at 24h were 0%,79%and 100%,respectively.The higher the preparation temperature is,the higher the adsorption removal rate of DCF will be.Therefore,BBC900 and WBC900 were selected to further study the adsorption performance of DCF.The adsorption removal rates of DCF on SBC,BBC900 and WBC900 at 3h were 94%,100%and 92%,respectively.Although the removal rate is not much different,compared with the overall trend and the theoretical maximum adsorption capacity calculated by Langmuir isotherm model,the removal efficiency of DCF was decreased in an order of BBC900,SBC,WBC900.Combined with the characterization results,this may be related to the specific surface area and the number of surface oxygen functional groups.The larger the specific surface area,the more active sites can be provided;the more the number of functional groups,the stronger the interaction force,which will be beneficial to the adsorption.