Elimination of amoxicillin by adsorption on coffee waste based activated carbon

In the present study, we describe the synthesis of coffee waste activated carbon (SAC) as potential material for the amoxicillin (AMOX) removal from aqueous solution. The conditions for synthesizing SAC were an impregnation weight ratio of raw biomass to KOH equal to 1:2 followed by activation at 800 °C for 1 h. The FTIR analysis and Boehm titration showed that SAC has 1.7627 and 1.5414 meq / g, respectively for acidic groups and of basic groups. The operating experimental parameters that govern the adsorption namely the temperature (288–318.16 K), intial pH (2.0–12.0), initial AMOX concentration Co (50–450 mg/L) and ionic strength were optimized. The adsorption isotherms were analyzed by various models. The experimental data were suitably matched to the Sips and Langmuir equations (R2 = 0.998). A Langmuir sorption capacity of 370 mg g−1 was determined, a value higher than that obtained on commercial activated carbon (CAC) employed for similarity purposes. The nature of the electrolyte was also examined with non-buffered AMOX solutions at different NaCl concentrations. The experimental results showed that AMOX adsorption is favored above pH 10. Otherwise, the absorption capacity is not influenced by the ionic strength of the electrolyte. The AMOX adsorption onto SAC was found to be exothermic and spontaneous under the operating parameters. The reusability of the adsorbent was tested by using appropriate chemical solvents and the results showed also that the sorption capacity decreases from 370 mg/g to 250 mg/g after four consecutive cycles.