The Effect of Competing Ions on the Sorption of Amoxicillin, Ciprofloxacin, and Sulfamethoxazole on Chitosan-Carbon Nanotube Hydrogel Beads

Abstract

The present work pertains to the synthesis of chitosan-carbon nanotube (CCNT) hydrogel beads using a two-step process for the uptake of amoxicillin (AMX), ciprofloxacin (CIP) and sulfamethoxazole (SMX) in the presence of varying concentration of sodium chloride (NaCl) and humic acid (HA) from 0 mg/L to 40 mg/L as competing ions. From the results obtained it was concluded that the increase in NaCl or HA concentration demonstrated antagonistic effects in the uptake of AMX, CIP and SMX on the synthesised CCNT hydrogel beads due to the formation of aggregates with an increase in ionic strength. Moreover, NaCl demonstrated the least effects on the uptake of the model antibiotics as compared to HA, indicating that NaCl ions exhibit minimal competitive effects with adsorbate molecules for active adsorption sites on CCNT hydrogel beads. Similarly, from the single factor analysis of variance results p-values of less than 0.05 were recorded for the uptake of AMX, CIP and SMX on CCNT hydrogel beads, explicitly indicating that there was a statistical difference between the means for the independent and dependent variables, thus cementing the negative effect of increasing ionic strength on the uptake of model adsorbates. Moreover, the findings of the present work suggest that the is need for a pretreatment stage aimed at eliminating co-existing contaminants prior to the application of solid-liquid adsorption for complete eradication of contaminants of emerging concern particularly antibiotics.