Preparation Of Alginate-based Bioadsorbents And Their Performance For The Treatment Of Wastewater Of Antibiotic Effluents

With the development of national economy,environmental protection has become an important construction project of sustainable development.Among them,the protection of water resource is particularly prominent in many factors caused by water pollution,indiscriminate discharge of sewage and industrial,medicine wastewater has become one of the major sources of pollution,especially the high concentration of antibiotics and anti-inflammatory wastewater.When these antibiotics and anti-inflammatory organic compounds reach certain concentrations in the environment,they seriously threaten the ecology and human environment.In recent years,more and more researchers pay much attention on the organic wastewater treatment and try to find a safe and efficient treatment method.Herein,this paper attempted to manufacture a series of alginate-based biological materials as the absorbents.In addition,the resulting adsorbents were characterized and their adsorption performances of antibiotics wastewater treatment were evaluated.?1?Mn@alginate composite microspheres were successfully prepared by using sodium alginate as raw materials.The as-obtained Mn@alginate products were characterized by FE-SEM,EDS and FT-IR.Whereafter,the Mn@alginate absorbents were used for the adsorptive removal of tetracycline hydrochloride from aqueous solutions.Various factors affecting the adsorption process,such as initial concentration of tetracycline hydrochloride,pH and contacting time were discussed,respectively.Moreover,the adsorption process was analyzed by the adsorption kinetics,isotherm models and adsorption thermodynamics.The regeneration of Mn@alginate was also evaluated.The results show that the higher initial concentration of tetracycline hydrochloride has lead to the greater equilibrium adsorption capacity.The adsorption amounts were further increased with the time prolonged.Strong acidity was not good for the adsorption of tetracycline hydrochloride onto the surface of Mn@alginate composite adsorbents.The adsorption process of tetracycline hydrochloride by Mn@alginate was found to be in better correlation with the pseudo-second-order kinetic equation and Langmuir isothermal model.Absorption of the tetracycline hydrochloride from aqueous solutions is spontaneous and endothermic,and they were dominated by chemical adsorption and physical adsorption simultaneously.The adsorptive enrichment of tetracycline hydrochloride onto the surface of Mn@alginate adsorbent could be effectively regenerated and recycled through Fenton-like reaction.?2?Alginate medium has been extensively used as absorbents due to its excellent properties like bio-compatibility,low toxicity,relatively low-cost,and ease of gelation.However,the practical application of pure alginate medium as adsorbent has been restricted since the saturated adsorbent has weak physical structure and could not be regenerated easily.In this study,a low-cost and renewable composite MnO₂@alginate/Mn adsorbent has been prepared facilely for the absorptive removal of antibiotic wastewater.The scanning electron microscope analysis?FE-SEM?,Fourier transform infrared?FT-IR?spectra analysis and X-ray diffraction?XRD?were used to characterize the samples.The norfloxacin?NOR?,frequently detected in wastewater and surface water with high concentrations,was used as an index of antibiotics to study the adsorption performance.More specifically,the batch absorption efficiency of MnO₂@alginate/Mn beads for NOR wastewater was evaluated by pH,contact time with different initial antibiotic concentration and the system temperature.Thus,the performance of absorption kinetic-dynamics was estimated by pseudo-second-order kinetic model and the pseudo-first-order kinetic equation.Langmuir and Freundlich isotherm equations were selected to obtain the equilibrium uptake capacity of adsorptive removal process.Parameters including?G⁰,?H⁰ and?S⁰ were utilized to describe the feasible adsorption process.To regenerate the saturated absorptive sites of MnO₂@alginate/Mn adsorbent,the heterogeneous Fenton-like reaction were trigged by introduction of H₂O₂.The experimental results showed that the in situ regenerating through heterogeneous Fenton-like reaction have exhibited an excellent recycling stability.The high activity of MnO₂@alginate/Mn and the simple fabrication make them attractive for the treatment of wastewater containing refractory organic compound,and also provide fundamental basis and technology for further practical application.?3?MnO₂@alginate-carbon composite microspheres were successfully prepared by the thermal cracking method.Various factors affecting the adsorption process,such as pH,initial concentration of diclofenac sodium?DCF?and adsorbent dosage were discussed,respectively.Moreover,the adsorption process was analyzed by the adsorption kinetics,isotherm models and adsorption thermodynamics.The regeneration of MnO₂@alginate-carbon was also evaluated.The results show that the higher initial concentration of diclofenac sodium has lead to the greater equilibrium adsorption capacity.The adsorption amounts are further increased with the initial concentration of DCF prolonged.Acidity is good for the adsorption of DCF onto the surface of MnO₂@alginate-carbon composite adsorbents.The adsorption process of DCF by MnO₂@alginate-carbon is found to be in better correlation with the pseudo-second-order kinetic equation and Langmuir isothermal model.Absorption of the DCF from aqueous solutions is spontaneous and endothermic,and they are dominated simultaneously.The adsorptive enrichment of DCF onto the surface of MnO₂@alginate-carbon adsorbent can be effectively regenerated and recycled through Fenton-like reaction.?4?The adsorption potential of MnO₂@alginate-carbon composite adsorbents to remove Doxyxycline?DC?from aqueous solution was investigated using fixed-bed adsorption column.The effects of pH?3.0¹1.0?,bed height?1³ cm?,inlet concentration(20³0 mg·L^-1)and feed flow rate(1³ mL·min^-1)on the breakthrough characteristics of the adsorption system were determined.The results showed that the highest bed capacity of 9.71 mg·g^-1 was obtained under the condition of pH 6.0,20 mg·L^-1 inlet DC concentration,1.0 cm bed height and 1 mL·min^-1 flow rate.The adsorption parameters were fitted to Thomas model and Yoon-Nelson model.The results fitted well to the three models with coefficients of correlation R²>0.980 at different conditions.The MnO₂@alginate-carbon composite adsorbents have desired regeneration ability and could be reused for four times.