Parameter optimization of tetracycline removal by vanadium oxide nano cuboids

Abstract Massive production and widespread use of antibiotics have led to concerns about negative outcomes for the environment and human health. In particular, tetracycline (TC) is a persistent and highly soluble chemical that threatens global water security. In this work, the utility of vanadium oxide nano cuboids (VONCs) as a mesoporous, non-toxic, stable, and low-cost material was studied for TC adsorption properties. Optimization of the experimental conditions for TC uptake was carried out using the response surface methodology (RSM) where the model showed that the adsorbent dose was the key variable affecting TC sorption. Moreover, the model indicated a 20% suppression in TC removal as the pH decreased from 9 to 3. The TC removal increased by 30% by increasing the adsorbent dose (0.1 - 0.5 g/L) and initial TC concentration (25 - 100 mg/L) values. RSM optimization afforded 100% adsorptive removal at the following conditions: pH = 4.1, mixing time of 44.5 min, VONCs dosage of 0.49 g/L for a fixed TC concentration (30.7 mg/L TC). Equilibrium sorption data for VONCs agreed well with the Langmuir model, where an estimated monolayer sorption capacity for TC (126.8 mg/g) was obtained. The separation factor (RL) for variable TC concentration covered a range of values (0.02 to 0.19) that is indicative of a favorable process. A study of the sorption mechanism revealed that the rate-controlling step of the sorption process depended on the mutual diffusion of VONCs and TC. The sorption of TC by VONCs is characterized by an exothermic process that was favorable at room temperature and TC removal showed a mild suppression (16%) in the presence of co-adsorbates in real wastewater.