Tetracycline removal by a natural biosorbent: optimization by response surface methods employing DOE/FFD design of the experiment
Aicha Naboulsi, Imane Naboulsi, Taoufiq Bouzid, Abdelali Grich, Abdelmajid Regti, Mamoune El Himri, Mohammadine El Haddad
Abstract
This study utilised activated carbon, synthesised with H3PO4 as an active agent (referred to as C-H3PO4), as an adsorbent for the removal of tetracycline (TC), a commonly used pharmaceutical compound. The activated carbon underwent characterisation through SEM-EDS, FTIR, and XRD analyses. The C-H3PO4 particles were found to range in size from 63 to 50 µm and possessed acidic functions within a surface area of 590 mmol/g. To assess the adsorptive performance of C-H3PO4 in relation to tetracycline, several operational parameters were investigated, including contact time, temperature, pH, concentration of the pharmaceutical compound, and C-H3PO4 dosage. Optimal conditions were determined as follows: a pH of 2.8, a TC concentration of 15 mg/L, a temperature of 308 K, and an adsorbent dosage of 90 mg, utilising the design of experiments (DOE/FFD) for parameter optimisation. In addition, the analysis of variance (ANOVA) and three-dimensional surface plots were created to evaluate the interaction between the factors and the ideal conditions for removing tetracycline. The maximum adsorption capacity of C-H3PO4 onto TC was found to be 7.41 mg/g. The experimental data were best fitted using the pseudo-second-order and Freundlich models, suggesting a multilayer physisorption phenomenon.