酸化赤泥吸附环丙沙星的特征、机理及过程优化

Adsorption of ciprofloxacin by acidified red mud: characteristic, mechanism and process optimization

为提高赤泥的资源化利用及抗生素有机废水的深度处理,以酸化赤泥为吸附剂、环丙沙星为目标污染物,研究了酸化赤泥吸附环丙沙星的条件、特征和机理.采用响应面法中Box-Behnken设计方法,以吸附温度、溶液pH值、环丙沙星初始浓度、酸化赤泥投加量为自变量,吸附量为响应值建立4因素3水平优化模型,确定了最佳吸附条件,并对吸附过程的动力学模型、等温线模型、热力学特性及吸附机理进行了研究.结果表明,溶液pH值、环丙沙星初始浓度、酸化赤泥投加量为影响吸附量的显著因素.酸化赤泥吸附环丙沙星的最佳条件为:温度45℃、pH=3.04、环丙沙星初始浓度29.20mg/L,酸化赤泥投加量3.40g/L,预测最大吸附量为7.30mg/g.酸化赤泥吸附环丙沙星的过程遵循伪二级反应动力学模型及Langmuir-Freundilich吸附等温线模型,经过拟合最大吸附量分别为7.90和7.35mg/g.根据Van Tehoff公式计算吸附热力学状态函数ΔG^0为-82.13^-94.37kJ/mol、ΔS^0为0.61J/(mol·K)、ΔH^0为100.25KJ/mol,吸附为自发进行的吸热反应.FTIR表明环丙沙星分子中—COO与酸化赤泥的Al—O键发生络合反应,C=O与Fe—O键发生微弱的静电或内球面键合作用.研究表明,酸化赤泥是一种极具潜力的廉价吸附剂,可用于处理抗生素污染废水.

In this paper,the adsorption conditions,characteristic and mechanism of ciprofloxacin on the acidified red mud were studied.A four-factor and three-level optimization model based on Box-Behnken design method was established to determine the optimum adsorption condition,and adsorption temperature,solution pH,ciprofloxacin initial concentration and acidified red mud dosage were as arguments and adsorption capacity as the response value.The kinetic model,isotherm model,thermodynamic property and mechanism of the adsorption process were discussed as well.The results showed that solution pH,ciprofloxacin initial concentration,acidified red mud dosage had significant effect on the adsorption process.The predicted maximum adsorption reached 7.30mg/g under the optimized conditions of 45℃,pH 3.04,ciprofloxacin initial concentration of 29.20mg/L,and acidified red mud dosage 3.40g/L.The adsorption was well fitted the pseudo-second-order reaction kinetics and Langmuir-Freundilich isotherm model,with the maximum adsorption capacity were 7.90 and 7.35mg/g,respectively.ΔG^0,ΔS^0 andΔH^0 were calculated by Van Tehoff equation as-82.13~94.37kJ/mol,0.61J/(mol·K)and 100.25kJ/mol,respectively.Ciprofloxacin adsorption on acidified red mud was a spontaneous endothermic process.Infrared spectrum showed that the complexation between carboxylate group of ciprofloxacin and Al-O bond of acidified red mud,and the weak electrostatic or inner-sphere bonding between keto group in ciprofloxacin and Fe-O in acidified red mud were attributed to the adsorption.This study showed that acidified red mud is a potentially low-cost absorbent for the treatment of antibiotic-contaminated wastewater.