Removal of Doxycycline from Water using Dalbergia sissoo Waste Biomass Based Activated Carbon and Magnetic Oxide/Activated Bioinorganic Nanocomposite in Batch Adsorption and Adsorption/Membrane Hybrid Processes

The carbonaceous adsorbents, an activated carbon (AC) and a bioinorganic nanocomposite (MAC), were prepared using Dalbergia sissoo sawdust as waste biomass, in this study. Both the adsorbents were characterized by FTIR, EDX, SEM, XRD, TG/DTA, surface area, and a pore size analyzer. The adsorbents were used for the removal of an antibiotic, doxycycline (DC) antibiotic, from wastewater in order to minimize a load of antibiotics in industrial effluents and consequently the drug resistance problem. Initially, the effectiveness of adsorbent was confirmed using batch adsorption experiments where isothermal models like Langmuir, Freundlich Temkin, Jovanovic, and Harkins–Jura were utilized to govern the maximum adsorption capacity of AC and MAC while pseudo-first- and second-order kinetic models were used to estimate the values of different kinetic parameters. Langmuir model best accommodated the equilibrium data whereas the pseudo-second-order kinetic model finest trimmed the kinetics data. The effect of pH on adsorption was also evaluated where maximum removal was observed between pH 5 and 7 by both adsorbents. The effect of temperature on adsorption was evaluated where the entropy change (ΔS(0)) comes out to have a numerically positive value whereas Gibbs free energy change (ΔG(0)) and enthalpy change (ΔH(0)) were negative indicating the spontaneous nature and feasibility of the procedure. The robust technology of membrane separation is rapidly replacing the conventional technologies but at the same time suffers from the problem of membrane fouling. As pretreatment, the AC and MAC were used in hybrid with ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes whereas permeate fluxes and percent retention of DC were compared for naked membrane operations and AC/membrane and MAC/membrane process. The permeate fluxes for MAC/membrane processes were greater as compared to AC/membrane and naked membrane processes showing the effectiveness of the bioinorganic composite as foul control and consequently recovery of DC from effluents. The percent retention of the UF membrane was lower as compared to NF and RO membranes. Improvement in percent retention for UF/AC, UF/MAC, NF/AC, NF/MAC, RO/AC, and RO/MAC was observed. The bioinorganic composite MAC contains a magnetic iron oxide which was effectively removed from slurry after use through the magnetic process and that was the main reason for high permeate fluxes in MAC/membrane operations.