Removal of acid orange-7 and ciprofloxacin from wastewater using a gemini surfactant-bentonite hybrid material

The g(16-4-16)-Bt hybrid material, prepared by intercalation of a gemini surfactant (butane-1,4-bis(hexadecyldimethylammonium) dibromide), g(16-4-16), with bentonite (Bt) clay, was used for the removal of acid orange-7 (AO-7) and ciprofloxacin (CPX) from wastewater. The batch sorption study suggested optimized conditions for the sorption at 298 K as pH 3 (AO-7) and 6 (CPX), AO-7/CPX concentrations = 10 mg L⁻¹, adsorbent dose = 2 g L⁻¹, equilibrium time = 60 min. (AO-7) and 120 min. (CPX). The g(16-4-16)-Bt hybrid material exhibited a removal efficacy of ≈ 98 % and 95.8 % towards AO-7 and CPX. With the rise in pollutant concentration (1–25 mg L⁻¹), the sorption capacity of g(16-4-16)-Bt showed a notable increase (from 0.57 to 12.07 mg g⁻¹ for AO-7 and 0.57 to 11.43 mg g⁻¹ for CPX). The sorption studies were explored in the presence of co-existing ions such as Mg²⁺, Ca²⁺, EDTA, bicarbonate, sulphate, and glycine. The removal of CPX was found to be minimally affected in the presence of Mg²⁺ and Ca²⁺ cations, and only a slight impact was found on the removal of AO-7. The sorption phenomenon followed the pseudo-second-order kinetics and showed agreement with the Langmuir isotherm. The maximum sorption capacity of g(16-4-16)-Bt hybrid material towards AO-7 and CPX was found to be 37.08 and 15.77 mg g⁻¹, respectively. Even after the fifth sorption-desorption cycle, the g(16-4-16)-Bt hybrid material sustained more than 75 % removal efficiency in both cases. Computational studies were carried out and compared with the experimental results, which showed a good agreement. The g(16-4-16)−Bt was found to be effective for the removal of AO-7 and CPX pollutants from wastewater, demonstrating its potential as a cost-effective and sustainable approach, which may help in environmental protection.