•Adsorbent was prepared from residue of desilicated rice husk which was waste producing silica white.•The adsorption capacity of ciprofloxacin was relatively higher comparing with others reporters.•Adsorption process was optimized using central composite design incorporated with response surface methodology.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 ΔG, ΔH and ΔS 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.The contact model of CPX adsorption on AC at different pH.Download high-res image (251KB)Download full-size image

In this research, the effects of water-soluble glucoamylase at four concentrations of 2.79, 5.58, 13.95, and 27.9 wt % on CO2 hydrate formation phase equilibrium have been investigated. Traditional isochoric method was employed in 300 mL autoclave to provide these phase equilibrium data. The results are also compared with the hydrate formation in pure water and tetra-n-butyl ammonium bromide (TBAB) solution. The concentration of glucoamylase for CO2 hydrate formation has optimum value. When the concentration of glucoamylase was 5.58 wt %, it has positive effect on lowering CO2 hydrate formation requirements. Compared with TBAB, the promotion effect of glucoamylase is a little bit milder. When the concentrations of glucoamylase were 27.9 and 13.95 wt %, the glucoamylase has inhibiting effect on hydrate formation. Compared with methanol, the inhibiting effect of glucoamylase system is a little bit milder.