Preparation Of Activated Carbon Based On Salix Psammophila And The Research On The Adsorption Behavior For Antibiotics From Aqueous Solution

Antibiotics?AN?are widely applied in industry,agriculture,medicine,animal husbandry and so on.Only a few antibiotics can be absorbed and metabolized by humans and animals.Most of them could discharge into the aquatic environment and threaten the ecological equilibrium and the health of human beings.In general,the adsorption was used to remove the AN from aqueous solution.Salix psammophila?SP?is a perennial shrub with low cost and high percentage of survival,which grows widely in arid and semi-arid areas.Salix psammophila was utilized as a precursor to prepare the activated carbon?SPAC?by chemical activation method using H₃PO₄ as the activating agent.Response surface methodology?RSM?based on Box-Behnken design?BBD?model was employed to optimize the prepared conditions of SPAC.The SPAC was used to remove the fluoroquinolone antibiotics?FQs?and sulfonamide antibiotics?SFs?.The effects of concentration of H₃PO₄,activation temperature and activation time on the adsorption performance?expressed by the adsorption capacity of ciprofloxacin hydrochloride?CIP?and norfloxacin?NOR?classified from FQs?were investigated.The optimum preparation conditions of SPAC1 were obtained using H₃PO₄ concentration of 67.84%,activation temperature of 567.48°C and activation time of 86.58 min.Similarly,the optimum preparation conditions of SPAC2 were obtained using H3PO4 concentration of 68.74%,activation temperature of 577.46°C and activation time of 48.81 min in response to the adsorption capacity of Sulfamethazine Sodium?SMS?classified from SFs.The SPAC1 and SPAC2 were characterized using the Thermogravimetric Analysis?TG/DTG-DSC?,Scanning electron microscope?SEM?,X-ray diffraction?XRD?,Fourier transform infrared spectrum?FT-IR?,specific surface area analysis?BET?and so on.The results of characterization showed the SPAC1 and SPAC2 had the BET surface area?SBET?of1328 m²/g and 1342 m²/g,respectively.The average pore size of SPAC1 and SPAC2was 3.706 nm and 3.711 nm,respectively.In addition,the abundant functional groups were found on the surface of SPAC1 and SPAC2?e.g.-OH?-COOH?.The adsorption behavior of CIP and NOR on the SPAC1 was explored.Influence of adsorbent dose,contact time,initial concentration,pH,temperature and ionic strength on the adsorption capacity of SPAC1 for CIP and NOR was investigated.The detail adsorption mechanism was investigated based on the isotherm and kinetic models.This results indicated the optimal adsorbent dose for adsorption both CIP and NOR on the SPAC1 was 0.01 g/L.The adsorption equilibrium time was 24 h and the optimal pH was 8.02 and 7.75,respectively.The Freundlich?Koble-Corrigan?K-C?and Dubinin-Radushkevich?D-R?models could be used to fit the adsorption process of CIP and NOR on the SPAC1.While the K-C model was the best fit to adsorption isotherms.The maximum monolayer adsorption uptake from Langmuir model was0.653 mmol/g and 1.149 mmol/g for adsorption CIP and NOR on the SPAC1 at 25oC,respectively.The kinetic research showed the pseudo-second-order and Elovich models were used to describe the kinetic process of adsorption CIP and NOR by the SPAC1.The best fitted kinetic model was Elovich model.The adsorption behavior of SMS on the SPAC2 was studied.The central composite design?CCD?under response surface methodology?RSM?was employed for the removal of SMS and the process parameters including adsorbent dose,contact time,pH and initial concentration of SMS were optimized.The optimum adsorption conditions were obtained using adsorbent dosage of 0.54 g/L,initial concentration of1.070 mmol/L,contact time of 8 h,pH value of 4.04,respectively.The thermodynamics,dynamics and adsorption mechanisms were explored under the optimum conditions.The process of adsorption SMS on the SPAC2 could be described by Freundlich,K-C and D-R models.While the best fitted isotherm was the K-C model.The maximum monolayer adsorption uptake from Langmuir model was1.127 mmol/g.The adsorption process followed pseudo-second-order model and Elovich model.The best fitted kinetic model was Elovich model.The results of the thermodynamic parameters showed that the adsorption process of SPAC1 and SPAC2 on the three antibiotics were spontaneous and endothermic.The intraparticle diffusion showed the film diffusion and intragranular diffusion together control the adsorption process of SPAC1 and SPAC2 for the three antibiotics.The main mechanism of adsorption CIP and NOR by SPAC1 was including ion exchange,hydrophobic effect,?-?electron donor-acceptor interactions??-?EDA?,electrostatic attraction,hydrogen bond and so on.The ion exchange,?-?EDA attraction and hydrogen bond were regarded as the main influencing factors on adsorption capacity of SPAC2 for SMS.The regeneration of SPAC1 and SPAC2 was studied.The results showed 0.1mol/L HCl could be used to the regeneration of adsorption saturated SPAC1 for CIP and NOR.After three cycles operations,the regeneration rates for SPAC1-CIP and SPAC2-NOR were 87.2%and 85.6%,respectively.While 0.1 mol/L NaOH could be used to the regeneration of adsorption saturated SPAC2 for SMS.After three cycles operations,the regeneration rates were 76.24%.