Co-modified MCM-41 as an effective adsorbent for levofloxacin removal from aqueous solution: optimization of process parameters, isotherm, and thermodynamic studies

Abstract

Antibiotics are emerging contaminants due to their potential risks to human health and ecosystems. Poor biodegradability makes it necessary to develop effective physical-chemical methods to eliminate these contaminants from water. The cobalt-modified MCM-41 was prepared by a one-pot hydrothermal method and characterized by SAXRD, N adsorption-desorption, SEM, UV-Vis DR, and FTIR spectroscopy. The results revealed that the prepared 3% Co-MCM-41 possessed mesoporous structure with BET surface areas at around 898.5 mg. The adsorption performance of 3% Co-MCM-41 toward levofloxacin (LVF) was investigated by batch experiments. The adsorption of LVF on 3% Co-MCM-41 was very fast and reached equilibrium within 2 h. The adsorption kinetics followed the pseudo-second-order kinetic model with the second-order rate constants in the range of 0.00198-0.00391 g mg min. The adsorption isotherms could be well represented by the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. Nevertheless, D-R isotherm provided the best fit based on the coefficient of determination and average relative error values. The mean free energy of adsorption (E) calculated from D-R model was about 11 kJ mol, indicating that the adsorption was mainly governed by a chemisorption process. Moreover, the adsorption capacity was investigated as a function of pH, adsorbent dosage, LVF concentration, and temperature with help of respond surface methodology (RSM). A quadratic model was established, and an optimal condition was obtained as follows: pH 8.5, adsorbent dosage of 1 g L, initial LVF concentration of 119.8 mg L, and temperature of 31.6 °C. Under the optimal condition, the adsorption capacity of 3% Co-MCM-41 to LVF could reach about 108.1 mg g. The solution pH, adsorbent dosage, LVF concentration, and a combination of adsorbent dose and LVF concentration were significant factors affecting the adsorption process. The adsorption thermodynamic functions were also determined. The negative ΔH (-33.50 kJ mol) and ΔS (-43.57 J mol K) suggested that the adsorption was an exothermic process accompanied by decreasing disorder. This study may indicate that 3% Co-MCM-41 is a promising adsorbent for removing emerging pollutants of LVF from water.

Cobalt and nickel uptake by silica-based extractants

“…[4,10,24,44] The calculated mean free energy, ED, can be used to determine the type of adsorption; if ED falls in the range 8 -16 kJ mol -1 , adsorption is dominated by chemical ion exchange, whereas below 8 kJ mol -1 , adsorption is dominated by physical forces. [45][46][47][48] The ED values for cobalt and nickel uptake are greater for S950 than for EBP-Si and are higher for cobalt than for nickel for both resins. In the case of S950, adsorption of hours.…”

De‐fluoridation of Polluted Water Using Aluminium Alginate Beads Doped with Green Synthesized ‘Nano SiO2+Nano CeO2‐ZrO2’, as an Effective Adsorbent

“…where q e = amount of adsorbed adsorbate, K d = distribution coefficient of the adsorption, R = gas constant and T = temperature in Kelvin as described in the literature. [28,29] From Van't Hoff plots (lnK d Vs1/T; Eq. (4)], K d values were obtained.…”

Efficient Removal of Levofloxacin Hydrochloride from Environment by UiO-66/CoSO4 Composites

“…为了提高 MOFs 吸附性能, 众多学者采用不 同手段对 MOFs 进行修饰, 得到性能优越的新型复合材 料, 并用于环境中污染物的吸附和降解 [7] . 左氧氟沙星是第三代人工合成类的氟喹诺酮类抗 生素 [8] , 由于抗菌效果好, 作用强, 容易被吸收, 被广泛 应用于临床之中 [9] . 研究表明, 左氧氟沙星被人类或动 物摄入后均不能被完全吸收, 多数以原体形式通过人体 废弃物进入环境, 造成严重水体污染 [10] .…”

“…因此, 去除环 境中残留的左氧氟沙星抗生素, 对保护水体及生态环境 至关重要. 吸附法是一种经济、环保、简单的废水处理 方式 [11,12] , 但是现有吸附剂对废水中左氧氟沙星的吸附 效果不佳, 价格昂贵且不易再生 [8,10,11,13,14] , 因此, 寻找 一种廉价、高效的吸附剂用以去除左氧氟沙星是许多研 究者的目标.…”