Preparation Of Lignin-based Porous Carbon And Its Adsorption Of Chloramphenicol In Water

Chloramphenicol（CAP）is detected more and more frequently in water,soil and even food,and the resistance genes brings pose a serious threat to humans and the environment.The adsorption method is currently one of the effective ways to remove chloramphenicol in water efficiently and quickly,but the high price of commercial activated carbon limits its application.Biochar has the advantages of widely available raw materials,high surface area and abundant functional groups,and is considered to be a potential environmentally friendly adsorbent.Sodium lignosulfonate（SLS）,a by-product of paper industry,was used as carbon source to prepare multi-functional porous carbon with high adsorption capacity,recoverability and high regeneration performance by adjusting parameters.BET,SEM,FT-IR,XRD,XPS and VSM were used to characterize and study its physical and chemical properties,and its behavior and mechanism were studied by adsorption of CAP.The research work and conclusions of this paper were as follows:（1）In this work,a simple preparation method using SLS as a precursor to make layered porous carbon was proposed.By adjusting the activation temperature and the mass ratio of the activator K₂CO₃to SLS,the two main activation conditions,porous carbons with different pore structures were prepared using a one-step method.The porous carbon PC-800-4 prepared under the conditions of activation temperature of 800℃and K₂CO₃/SLS mass ratio of 4 has a high specific surface area(1305.5 m²g^-1)and pore volume(0.758 cm³g^-1).At 303 K,at a lower initial concentration of CAP(120 mg L^-1),the maximum adsorption capacity of PC-800-4 was 534.0 mg g^-1,which was a great improvement compared with other works.The analysis of the adsorption data showed that the Langmuir isotherm model and the pseudo-second-order kinetics perfectly describe the adsorption isotherm.Thermodynamic analysis showed that the adsorption process of CAP was spontaneous and endothermic.In addition,PC-800-4 still maintained good adsorption performance in a wide pH range,and had good resistance to interference from ions and humic acid.This study demonstrated several advantages that could be brought about by preparing lignin-based porous carbon through a one-step method,including:1)The one-step activation method greatly simplified the manufacturing process of porous carbon materials and reduced the cost and time of preparation.2)Economical,abundant carbon raw materials and practicality made PC-800-4expected to become a large-scale practical adsorbent.（2）In order to break the limitation of increasing the activation temperature and increasing the amount of K₂CO₃to increase the adsorption capacity of porous carbon to CAP,melamine was used to prepare N-doped porous carbon materials on the basis of the previous step.PC_N-0.5 prepared under optimal conditions has a higher BET surface area(2567.9 m²g^-1)and pore volume(1.499 m³g^-1),which was nearly double that of PC-800-4.The adsorption behavior conformed to the Langmuir isotherm model and the pseudo-second-order kinetic model.Due to the improvement of the pore structure,the adsorption capacity increased from534.0 to 719.3 mg g^-1under the same conditions,the adsorption rate parameter K₂increased by 85%,and the saturated adsorption capacity reached 95%within 120 minutes.PC_N-0.5 can maintain its high-efficiency adsorption capacity for CAP in an environment of acid,alkali,0.1M metal ions and high humic acid.After 4 desorption-regeneration cycles,PC_N-0.5 still had87.3%of the original adsorption capacity,which solved the problem of poor regeneration performance and improves the scope of application.（3）In order to solve the recovery performance of the material and improve its application in practical engineering,on the basis of the previously prepared N-doped porous carbon with high adsorption amount,the material was given magnetism by adding ferric nitrate nonahydrate.PC_N,Fe-0.5 prepared under optimal conditions can be quickly separated from water by a magnet within 10s,and had a high BET surface area of 2553.8 m²g^-1and a pore volume of 1.776 m³g^-1.At 303 K,the adsorption capacity decreased from 719.3 to 633.5mg g^-1than without Fe doping,but increased to 681.3 mg g^-1at 308 K,indicating that PC_N,Fe-0.5 were more suitable for high temperature Under the conditions of adsorption.The adsorption behavior of PC_N,Fe-0.5 on CAP conformed to the Langmuir isotherm model and the pseudo-second-order kinetic model,and also had good anti-environmental interference and regeneration performance.In addition,PC_N,Fe-0.5 has the potential to catalyze organic pollutants with the PMS system in addition to their high adsorption performance.