Cellulosic materials for the removal of ciprofloxacin from aqueous environments

Abstract

The feasibility of using cellulose from Pinus spp. sawdust from Zomba, Malawi, treated with commercial and lemon-derived citric acid (CA) for ciprofloxacin (CFX) adsorption from water has been tested. Different CA concentrations were used on NaOH-pretreated sawdust for cellulose esterification. The material was analysed using a variety of techniques. Adsorption tests for CFX were performed using the batch method, and the data were analysed using Langmuir, Freundlich, and Temkin’s isotherms. The Fourier transform infrared spectroscopy (FTIR) and point of zero charge results showed surface charges increasing (hydroxyl, −OH, and carboxyl, −COOH groups) due to the CA reaction. The Temkin model was the best fit for the experimental data with R 2 test values of 0.9515, while pseudo-second-order was the best fit (R 2 = 0.9999) in an exothermic adsorption process. The adsorption efficiency was 83% on 0.8 g of the material at pH 4 in 20 mL (20 mg·L−1) CFX. The different CA concentrations during sawdust treatment had a negligible impact on morphology. A regression analysis (R 2 and p-values) of structural data showed that the particle size, distance, and crystallinity index had negligible impact, while surface charges and functional groups had a significant impact on adsorption. Overall, the adsorption of CA-treated sawdust material on CFX is satisfactory.

Keywords

• pharmaceutical pollutants
• ciprofloxacin
• citric acid-modified sawdust
• pinus sawdust decontamination