Preparation, characterization, and application of activated carbon from low-cost material for the adsorption of tetracycline antibiotic from aqueous solutions

In this study, a new zinc chloride (ZnCl₂) impregnated activated carbon (Zn-AC) was prepared from oak charcoals as low-cost material and used as adsorbent for tetracycline (TC) adsorption. The Zn-AC was characterized using field emission-scanning electron microscope, powder X-ray diffraction, and CHNS-O analyses. Specific surface area of the adsorbent was also measured using the Brunauer, Emmett and Teller (BET) isotherm model. The TC adsorption onto the Zn-AC was investigated as a function of solution pH, adsorbent dosage, and inorganic cations (Li⁺, K⁺, Mg²⁺, Ca²⁺, Ni²⁺, and Fe³⁺) and anions (HCO₃⁻, NO₃⁻ and SO₄²⁻) that could interfere in the adsorption of TC. The adsorbate solution pH had no considerable effect on TC adsorption. The adsorption of TC onto the adsorbent was relatively fast and reached the equilibrium after about 120 min. The results showed that all studied cations and anions decreased TC adsorption onto the Zn-AC, but this decrease in TC adsorption was strongly significant for Fe³⁺ and Ni²⁺ ions. The general order kinetic model and the Redlich–Peterson isotherm model provided the best fit to the experimental data. The maximum amount of TC adsorbed onto the Zn-AC (Q_max) is 282.06 mg g⁻¹, indicating this adsorbent is a good adsorbent for the removal of TC from aqueous solutions.