Batch Experimental Studies and Statistical Modeling for the Effective Removal of Tetracycline from Wastewater Using Bimetallic Zn–Cu-Metal–Organic Framework@Hydrogel Composite Beads

Antimicrobial resistance (AMR) is on an upsurge as more and more broad-spectrum antibiotics are being used haphazardly, resulting in imbalances in the ecosystem and disrupting common/systematic clinical protocols. To combat this issue, metal-organic framework embedded zinc-copper-benzenedicarboxylate@calcium alginate composite beads (Zn-Cu-BDC@CA CBs) were synthesized and utilized for the adsorption of tetracycline (TC) from water. The surface morphology, presence of functional groups, surface area, and thermal stability of Zn-Cu-BDC@CA CBs were evaluated by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and thermal gravimetric analysis (TGA), respectively. Batch adsorption experiments were also carried out to optimize the adsorption performance of Zn-Cu-BDC@CA CBs for TC by adjusting the key parameters, including pH of the solution, contact time, adsorbent dosage, temperature, and initial concentration of TC. From the RSM model, 96.8% removal of TC takes place under the optimum conditions (pH = 7.3, mass = 17.2 mg, concentration = 21.3 ppm, time = 3.4 h, and temperature = 31.8 °C), which aligns closely with the experimental batch study, where the addition of 20 mg of adsorbent to a 20 mL TC solution (20 mg/L) at a pH of 7 and a temperature of 27 °C yielded an impressive TC removal efficiency of 96.55% within 180 min. Zn-Cu-BDC@CA CBs possess homogeneous adsorption surfaces, and TC is adsorbed via monolayer chemisorption, according to the results derived from the Langmuir isotherm model and pseudo-second-order kinetic model. The thermodynamic analysis indicated that the adsorption process is both endothermic and spontaneous. In their entirety, the synthesized Zn-Cu-BDC@CA CBs exhibit certain operational advantages, such as simple separation, satisfactory adsorption performance, and decent recyclability, indicating their viability for industrial application of elimination of TC residues from aquatic environments.