Municipal solid waste biochar-bentonite composite for the removal of antibiotic ciprofloxacin from aqueous media

This study investigates the adsorption of ciprofloxacin (CPX) onto a municipal solid waste derived biochar (MSW-BC) and a composite material developed by combining the biochar with bentonite clay. A bentonite-MSW slurry was first prepared at 1:5 ratio (w/w), and then pyrolyzed at 450 °C for 30 min. The composite was characterized by scanning electron microscopy (SEM), Powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy before and after CPX adsorption. Batch experiments were conducted to assess the effect of pH, reaction time and adsorbate dosage. The SEM images confirmed successful modification of the biochar with bentonite showing plate like structures. The PXRD patterns showed changes in the crystalline lattice of both MSW-BC and the composite before and after CPX adsorption whereas the FTIR spectra indicated merging and widening of specific bands after CPX adsorption. The optimum CPX adsorption was achieved at pH 6, and the maximum adsorption capacity of the composite calculated via isotherm modeling was 190 mg/g, which was about 40% higher than the pristine MSW-BC. The Hill isotherm model along with pseudo-second order and Elovich kinetic models showed the best fit to the adsorption data. The most plausible mechanism for increased adsorption capacity is the increased active sites of the composites for CPX adsorption through induced electrostatic interactions between the functional groups of the composite and CPX molecules. The added reactive surfaces in the composite because of bentonite incorporation, and the intercalation of CPX in the clay interlayers improved the adsorption of CPX by the biochar-bentonite composite compared to the pristine biochar. Thus, MSW-BC-bentonite composites could be considered as a potential material for remediating pharmaceuticals in aqueous media

Characterization of aqueous Pb(II) and Cd(II) biosorption on native and chemically modified Alstonia macrophylla saw dust

This study was conducted inorder to understand the mechanism of Cd and Pb adsorption in aqueous solutions by raw and modified saw dust (SD) of Alstoniamacrophylla. The biosorbent was characterized by Boehm titration, specific surface area, scanning electron microscopy (SEM), X-ray energy dispersion (EDAX), and Fourier transform infrared (FTIR) analyses. SD was treated using organic acids and bases. Batch studies were conducted for raw and modified SD to determine the effect of initial concentration, pH, ionic strength, and contact time on metal adsorption. The specific surface area and total basic and acidic groups of SD were 77 m2/g and 1521 and 2312 µmol/g, respectively. The adsorption of both metals onto SD was pH dependent. No ionic strength dependency was observed in adsorption of Cd and Pb at pH >6, indicating inner sphere surface complexation. Monolayer adsorption is dominant in both metal sorptions by SD. Furthermore, there is no competition between metals on adsorption and raw SD was found to be suitable for removal of Cd and Pb as compared to organic acid– or base-treated SD. Maximum adsorption capacity of SD for Cd and Pb were 30.6 and 204.2 mg/g, respectively. Results indicate that the A.macrophylla SD can be considered as a potential material for metal ion removal from wastewater