Antibiotic Adsorption by Acid Enhanced Dialium guineense Seed Waste

Abstract

The pollution of water bodies with ciprofloxacin (CF) and other antibiotics has resulted in undesirable characteristics, such as color, odor and microbial resistance in environmental waters. Using agricultural waste as biosorbents for the removal of antibiotics from wastewater is a promising treatment approach. This research was based on the treatment of CF-polluted water by utilizing acid-modified Dialium guineense (tamarind) seed waste (HA-DGS), prepared by hydrochloric acid treatment of Dialium guineense seed (DGS). HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. The DGS and HA-DGS were characterized by the FTIR, SEM, EDX, TGA and BET analyses. The acid modification was optimized by the application of response surface methodology using central composite design. Batch methodology showed that HA-DGS had higher CF uptake than DGS at variations of pH, temperature, contact time, adsorbent dosage and CF concentration. The Freundlich isotherm with R2 > 0.9795 was more applicable to both adsorbents, while DGS conformed to the pseudo-second-order kinetic (R2 > 0.9939) and HA-DGS (R2 > 0.9085), to the pseudo-first-order kinetics. Thermodynamics showed a physical and exothermic uptake of CF on the adsorbents. HA-DGS exhibited a maximum CF uptake of 125 mg/g, which was higher than most adsorbents reported in the literature. Quantum chemical parameters and condensed Fukui functions revealed efficient interaction between CF molecules and the prepared materials. Over 60% desorption of CF was obtained from the CF-loaded adsorbents using water and HCl solution. The results of this research showed HA-DGS as an efficient, low-cost, waste material that can be optimally valorized in the treatment of wastewater contaminated with CF.