Sustainable water remediation using nano-engineered ZnFe₂O₄/tea waste magnetic composite for efficient dye removal: A mechanistic approach

This research investigates the preparation of an environmentally sustainable adsorbent derived from tea waste and zinc ferrite nanoparticles (ZnFe 2 O 4 /TW) for removing Coomassie blue (CoB) and Celestine blue (CB) dyes from simulated contaminated water. The ZnFe 2 O 4 /TW was produced using tea waste and zinc ferrite nanoparticles through simple co-precipitation technique. Characterization of the ZnFe 2 O 4 /TW was conducted using various techniques, including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy with Energy-dispersive X-ray spectroscopy (SEM-EDX), Vibrating-sample magnetometer (VSM) and Transmission electron microscopy (TEM). Batch adsorption experiments were carried out to determine the influence of ZnFe 2 O 4 /TW on CoB and CB dyes uptake under different experimental conditions, such as material dosage, dye solution pH, contact duration, initial dyes concentration, and temperature. Equilibrium data was evaluated using the linear forms of Langmuir, Freundlich and Temkin isotherm models and revealed the highest Langmuir adsorption capacity of 3.58 mg g −1 and 14.72 mg g −1 for CoB and CB dyes, respectively, at 318 K. Kinetic studies, with pseudo-first order, pseudo-second order, Intraparticle diffusion and Film diffusion models, indicated that the adsorption process was more appropriately described by the pseudo-second order kinetics further indicated that rate-limiting step in a sorption process might be chemisorption involving valence forces through sharing or exchange of electrons between the material and dyes. The thermodynamic evaluation indicated the spontaneous adsorption in the investigated temperature range, with endothermic behaviour for CoB and exothermic for CB (ΔH = +118.42, −29.94 kJ/mol for CoB and CB respectively). Overall, the synthesised ZnFe 2 O 4 /TW presents a promising and cost-effective adsorbent with potential for the adsorptive treatment of CoB and CB dyes.