Amino Modification Of Biomass Activated Porous Carbons And Study On The Mechanism Of Sulfonamide Antibiotics Adsorption In Water

In recent years,increasing concerns related to the safety problems and environmental risks caused by antibiotics have been aroused.In terms of antibiotics production and application,China has far exceeded other countries due to the widespread abuse of antibiotics.However,most antibiotics cannot be completely absorbed by the human,animals and plants,and eventually enter the environmental ecosystem in different forms,especially in the aquatic environment.Among them,the residues of sulfonamide antibiotics in water are generally high,and their biotoxicity and pollution to the water environment should not be underestimated.Biomass activated porous carbons?BPCs?represent a class of carbon material obtained by high temperature calcination and activation of biomass raw materials in the absence of oxygen or limited oxygen conditions.Due to their unique pore structure and large specific surface area,BPCs are often used as viable adsorbents for the removal of organic pollutants in wastewater treatment.In this dissertation,a series of activated carbon?BPCs?and amino-functionalized porous carbon materials?NH₂-BPCs?were developed via a facile chemical modification method.Adsorption kinetics and thermodynamic system were used to study the difference in the adsorption performances of BPCs and NH₂-BPCs.Moreover,the adsorption mechanism of amino modified activated porous carbon for sulfonamides adsorption was extensively discussed.The results showed that:?1?BPCs prepared by chemical activation using KOH possessed high specific surface area and abundant microporous structures.The highest specific surface area reached 1707 m²·g^–1?BPC-2?.Meanwhile,the surface micropore structures of BPCs were improved,such as tighter pore structure and more uniform distribution of micropores.The specific surface area of NH₂-BPCs was further increased to 2039 m²·g^–1?NH₂-BPC-2?.?2?Sulfadiazine?SDZ?was selected as the target pollutant.The adsorption performances of BPCs and NH₂-BPC were evaluated by the fitting parameters of adsorption kinetics and adsorption thermodynamics.The results showed that the equilibrium adsorption capacity?q_e? of NH₂-BPCs was slightly lower than that of BPCs,but with a higher adsorption rate,indicating that the modified activated porous carbon could bind to SDZ more quickly.In terms of adsorption thermodynamics,the saturated adsorption capacity?q_m?of BPC-2(124.6 mg·g^–1)was the highest according to Langmuir model fitting,but the K_L value was low,which indicated the adsorption affinity of BPC-2 to SDZ at lower concentration was weak.The q_m of NH₂-BPCs was generally decreased,whereas the K_L was about twice higher than that of BPCs.These results suggested that amino modification increased the adsorption affinity of adsorbents to pollutants.?3?The decrease of adsorption capacity of NH₂-BPCs was closely related to solution pH.By means of pH control,it was found that the adsorption rate and the adsorption capacity of NH₂-BPCs increased when pH was less than 5.0.When pH>7.0,the adsorptive capacity of NH₂-BPCs decreased,however the initial adsorption rate was largely improved,which indicated that the positive effect of amino modification on the adsorptive capacity of activated carbon was applicable to a wide range of pH conditions.In addition,NH₂-BPCs was able to maintain excellent adsorption properties at various temperature?15-55??,initial concentrations(1.0-20 mg·L^–1),and different antibiotic types.It was concluded that amino modification could be an effective method to increase sulfonamides adsorption on BPCs and NH₂-BPCs.?4?The sulfonamides adsorption on BPCs/NH₂-BPCs counted mainly on thepdonor-receptor interaction?p-pEDA?,electrostatic interaction,hydrophobic and hydrophobic interactions.The amino modification provided a reversedpdonor-acceptor interaction and a reverse hydrogen bonding forces,thereby enhancing the adsorption affinity between the BPCs/NH₂-BPCs and the sulfonamide antibiotics,and improving the adsorption rate of BPCs and NH₂-BPCs.Under alkaline conditions,the decrease of adsorption capacity of NH₂-BPCs was mainly due to electrostatic repulsive forces and hydrophobic interactions.In summary,amino modified activated carbons have shown excellent adsorption performances for sulfonamide antibiotics in water.Especially in acidic conditions,the equilibrium adsorption capacity and adsorption rate have been significantly increased.Therefore,as a class of efficient and stable adsorbents,amino modified activated carbons show broad application prospects in the treatment of antibiotic wastewater and related fields.