Adsorption performance and optimization by response surface methodology on tetracycline using Fe-doped ZIF-8 loaded with multi-walled carbon nanotubes

A metal-organic framework material, an iron-doped ZIF-8 loaded with multi-walled carbon nanotubes (FZM), was fabricated and used to adsorb tetracycline (TC) in this investigation. The adsorption impact and mechanism of TC on FZM were revealed using batch adsorption experiments and characterization analyses. The effects of Fe doping amount, pH, temperature, beginning concentration, and coexisting ions on the adsorption effect of TC were explored. It was discovered that Fe doping amount of 75 mg, pH of 6, and initial concentration of 100 mg/L produced the optimum adsorption effect. TC adsorption was also enhanced by the presence of Ca2+. The adsorption process of TC on FZM followed the pseudo-second-order (PSO) kinetic and Freundlich isotherm models, indicating that chemisorption was the dominant factor in the removal process of TC and the reaction was multilayer adsorption, with a theoretical maximum saturation capacity of 1111.11 mg/g fitted according to the Langmuir model, which was better than most other adsorbents. The procedure of TC adsorption on FZM. The adsorption process on FZM is a spontaneous, heat-absorbing process, and the adsorption capacity increases as the temperature rises. According to the findings of the FTIR study undertaken before and after adsorption, the mechanism of TC on FZM is predominantly intermolecular hydrogen bonding, surface complexation, π-π interactions, and electrostatic interactions. The projected adsorption capacity of TC was 599.78 mg/g under optimal adsorption circumstances of pH 7.1, temperature 312.5 K, and injection amount 64.43 mg/L, with a divergence of 1.73 % from the actual value, according to the response surface optimization studies. Furthermore, FZM has high reusability, and after four cycles of trials, the adsorption capacity of TC on FZM may still be greater than 370 mg/g, with a 15% loss. The cost of treating 100 mg/L of TC effluent was estimated to be around 8.35 US$/m3, indicating that FZM had excellent application possibilities for TC removal.