La-Doped ZnFe2O4/NiWO4-D400-MMT/PMMA-CMS Nanocomposites for Amoxicillin Adsorption from Aqueous Solutions

Pharmaceutical antibiotics in aquatic systems have led to a need for effective, re-usable and highly structurally stable materials for contaminant removal purposes. In this study, hybrid nanocomposites based on multifunctional nanocomposites with NiWO4 and La-doped ZnFe2O4 loaded in the matrix of montmorillonite/PMMA/CMS modified with Jeffamine-D400 were prepared and investigated for removal of amoxicillin (AMX) from water solution. The formation of heterogeneous structures was confirmed by FTIR, XRD, SEM–EDX, TEM and zeta potential techniques. There was an increase in the basal spacing of MMT from 6.9 Å for D400-MMT to 9.3–9.4 Å after the incorporation of the polymeric and inorganic phases. The adsorption efficiency was in the order S3 (La-doped ZnFe2O4/NiWO4@PMMA/CMS@D400-MMT) > S2 (NiWO4@PMMA/CMS@D400-MMT) > S1 (PMMA/CMS@D400-MMT). The adsorption efficiency of S3 was about 98% at pH 5. The kinetic study revealed that AMX adsorption on the material was influenced by several mechanisms of surface adsorption, mass transfer through the boundary layer, and intraparticle diffusion. At the initial concentration of AMX of 300 mg L−1, the experimentally obtained equilibrium adsorption capacities of S1, S2, and S3 were about 250, 265, and 290 mg g−1, respectively. The nonlinear isotherm analysis revealed that the adsorption data can be described more precisely using the Langmuir model. The maximum adsorption capacities obtained from the isotherms according to the Langmuir model were 278.12, 295.73, and 323.17 mg g−1 for S1, S2, and S3, respectively, while a lesser correlation coefficient was obtained for the Freundlich model. The increasing adsorption capacity obtained from the Langmuir isotherm from S1 to S3 confirms the beneficial effect of NiWO4 and La-doped ZnFe2O4 on the adsorption ability of the composite. Five repeated adsorption–regeneration cycles showed that after five adsorption cycles, S3 retained about 82% of its initial adsorption capacity.