A sustainable layered double hydroxide-pine cone biochar (LDH/PCBC) composite for enhanced removal of ciprofloxacin from water

Abstract

To address ciprofloxacin's (CPF) persistent presence in water and potential ecological and health hazard, the challenge is to develop an effective method for its removal from wastewater. This work is aimed at optimizing the adsorptive removal of ciprofloxacin (CPF) utilizing a layered double hydroxide pine cone biochar composite (LDH/PCBC). Response surface methodology (RSM) is employed to design the experiments to obtain optimal experimental conditions for improved adsorption processes. The CPF removal efficiency of LDH/PCBC from aqueous solution is found to be 97.6% under the optimized conditions (pH = 7, adsorbent dose = 0.45 g L⁻¹, initial CPF concentration = 52 mg L⁻¹ and temperature = 303 K). The Freundlich isotherm confirms the best fit, and the Langmuir adsorption capacity of the LDH/PCBC is determined to be 476.2 mg g⁻¹ at 303 K. The pseudo-second-order model fitted the best for adsorption kinetics, suggesting that the adsorption process is directed by chemisorption. The thermodynamic investigation confirmed the endothermic and spontaneous adsorption process (ΔH° = 56.9 kJ and ΔG° from −3.2 kJ at 278 K to −10.8 kJ at 318 K). The study reveals that LDH/PCBC can be reused effectively with insignificant loss of removal efficiency (∼6%). The cost of the development and large-scale application of LDH/PCBC for the removal of CPF is $988.75 per ton. The results indicate that the LDH/PCBC outperforms the reported adsorbents for sustainable removal of CPF from aqueous solutions. This is the first report on the use of LDH/PCBC as a cheaper and environment friendly method for the removal of CPF from water.