Preparation Of Porous Carbon Materials Derived From Biomass And Its Adsorption Performance Study On Tetracycline

Antibiotics have been extensively applied in human disease treatment and livestock production.However,they may be discharged into the environment in their original forms or metabolites by the fecaluria of patients,livestock,and poultry,not only causing soil and water contamination,but also threatening human health through food chains.In recent years,porous carbon materials are recognized as promising adsorbents used to adsorb antibiotics from wastewater on the basis of their high specific surface area,developed pore structure,and controllable pore structure and pore size.However,concerning the carbon source,the porous carbon materials derived from biomass are scarcely reported.Therefore,in this research,porous carbon materials derived from different biomass sources are prepared by the hydrothermal-high temperature activation method and the soft template method to study the adsorption performance of tetracycline(TC)used as the target pollutant.Firstly,the porous carbon material(HSBC-600)derived from excess activated sludge(wastewater treatment plant)is prepared by the hydrothermal-high temperature activation method,and the direct pyrolysis sludge biochar(PSBC-600)is also prepared for controlling experiments.The results show that sludge porous carbon has the best adsorption performance of TC as the activation temperature is 600℃.Hydrothermal pretreatment can increase the specific surface area and pore volume of porous carbon(HSBC-600:133.4 m~2/g and 0.237cm~3/g;PSBC-600:114.6 m~2/g and 0.159 cm~3/g)and the adsorption capacity of TC.It is noted that the Freundlich isotherm and pseudo-second-order kinetic models better describe the experimental data,indicating that the adsorption process of TC onto HSBC-600 and PSBC-600 is multi-layer adsorption and involves chemisorption.The results of thermodynamic study show that the adsorption process is spontaneous and endothermic,causing an increase in the degree of disorder.All adsorption mechanisms may include pore filling,hydrogen bonding,electrostatic force,π-πinteraction and complexation.The higher adsorption capacity of HSBC-600 may be due to the higher specific surface area and pore volume providing more active sites,in which theπ-πinteraction plays a major role.To further improve the adsorption capacity of TC,batatas is directly used as carbon precursor to synthesis a novel mesoporous porous carbon material(HMC-800)through a soft-template assisted hydrothermal route using polyethylene-polypropylene glycol(F127)as soft-template agent.Meanwhile,the biochar without F127 and direct pyrolytic biochar are prepared for comparison.The results show that the HMC-800 displays the highest specific surface area(286.3 m~2/g)and total pore volume(0.249 cm~3/g),manifesting the introduction of F127 can result in formation of well-developed pore structures.Regarding adsorption properties,the HMC-800 outperforms other biochar samples for TC removal.When the solution is near-neutral p H,it is favorable for TC removal.In addition,the results show that applying a pseudo-second order kinetic model best describes the reaction kinetic behavior,indicating that chemisorption is involved between TC molecules and HMC-800.The Freundlich isotherm equation closely models the recorded adsorption behavior,indicating that the TC adsorption process is multi-layer adsorption.Based on Langmuir isotherm model,the theoretical maximum adsorption capacity is measured to be as much as 238.7 mg/g.The results of thermodynamic study show that the adsorption process is spontaneous and endothermic,causing an increase in the degree of disorder.Here,possible adsorption mechanisms include pore filling,electrostatic force,hydrogen bonding,n-πorπ-πinteraction,of which the pore filling,hydrogen bonding and n-πinteraction mechanisms may be prevailing.Furthermore,the HMC-800 performs better in regeneration and reuse experiments,making it a promising adsorbent material for TC removal from wastewater.