Response surface methodology approach for optimization of ciprofloxacin adsorption using activated carbon derived from the residue of desilicated rice husk

Abstract Activated carbon (AC) derived from residue of desilicated rice husk (DRH) was investigated for the removal of antibiotic ciprofloxacin (CPX) from liquid phase. Operating variables including contact time, adsorbent dosage, CPX concentration and solution pH were optimized using central composite design (CCD) under response surface methodology (RSM) approach. The optimum parameters for CPX adsorption were found out to be 306.9 min contact time, 0.40 g L − 1 adsorbent dosage, 314.8 mg L − 1 CPX concentration, pH 7.92 and the predicted adsorption uptake was 454.68 mg g − 1 . The experimental equilibrium data was found to fit the Langmuir isotherm model and Koble-Corrigan model well. The maximum monolayer adsorption uptake of AC was 461.9 mg g − 1 at 298 K. The thermodynamic parameters including Δ G , Δ H and Δ S also were investigated. Kinetic models were studied and pseudo-second-order was proved to be the best fit to adsorption kinetic data. The AC was characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and Fourier transform infrared spectroscopy (FTIR). The sorption mechanism was elucidated at different pH. This study indicated that AC based on DRH was a promising candidate because of the lower cost and larger adsorption capacity for the removal of CPX from liquid phase.