SYNTHESIS AND CHARACTERIZATION OF β- CYCLODEXTRINE CAPPED MAGNETIC NANOPARTICLES ANCHORED ON CELLULOSIC MATRIX FOR REMOVAL OF HEXAVALENT CHROMIUM FROM MIMICKED WASTEWATER

Abstract

Water is one of the most abundant features on Earth covering up to 70% of Earth's crust but only less than 1% of this water is fit for human consumption. Water can be polluted by both organic and inorganic matter. Hexavalent chromium (Cr(VI)) one of the inorganic pollutant is an important component in many industrial process finds its way into water bodies posing health problems which include lung cancer and inhibition of DNA and RNA in biological systems. This study thus focused on the preparation, characterization, and application of a novel nanocomposite adsorbent, CNC-Fe3O4NP CD, for the removal of Cr(VI) from aqueous solutions. The cellulose used in this research was extracted from Typha angustifolia and hydrolized to cellulose nanocrystals (CNCs) using 32% H2SO4. The prepared and characterized cellulose nanocrystals, were incorporate onto iron oxide nanoparticles using co-precipitation method and functionalized with β-cyclodextrin by shear homogenization. Fourier Transform Infrared Spectroscopy (FTIR) identified the characteristic peaks of cellulose functional groups, including O-H stretching at 3309 cm⁻¹, C-H stretching at 2892 cm⁻¹, and C-O-C stretching at 1034 cm⁻¹. Transmission Electron Microscopy (TEM) revealed that the CNCs had nano-scale dimensions, with an average particle size of 98.57 ± 2.54 nm. X ray Diffraction (XRD) analysis confirmed the successful conversion to crystalline form, with a crystallinity index of 77.41%. The characterization of the nanocomposite (CNC Fe3O4NP) with Scanning Electron Microscopy (SEM) and TEM analyses showed a uniform distribution of Fe3O4 nanoparticles, with an average particle size of 16.82 nm. The nanocomposite exhibited strong magnetic properties, as evidenced by Vibrating Sample Magnetometer (VSM) analysis, which recorded a magnetization value of 64.56 emu/g. Batch adsorption studies were conducted under varying conditions, including pH, adsorbent dosage, initial Cr(VI) concentration, contact time, and temperature. The optimal conditions for Cr(VI) removal were determined to be a pH of 2, an adsorbent dosage of 1.0 g, an initial Cr(VI) concentration of 20 mg/L, a contact time of 35 minutes at room temperature. Under these conditions, CNC-Fe3O4NP-CD achieved a maximum Cr(VI) removal efficiency of 97.45%. In the presence of competing ions such as Cu²⁺, Zn²⁺, and Pb²⁺ at a concentration of 20 mg/L, the Cr(VI) removal efficiency of CNC Fe3O4NP-CD decreased to 30.22%, 30.22%, and 40.49% respectively. Regeneration studies demonstrated that CNC-Fe3O4NP-CD could be reused effectively over multiple adsorption-desorption cycles. Based on kinetic study, the experimental data fitted best with the pseudo-second-order kinetic model, which exhibited high linear regression coefficients (R² > 0.98) across all tested conditions. Equilibrium isotherm studies fitted well with the Langmuir isotherm model, indicating monolayer adsorption on a homogeneous adsorbent surface. The Freundlich and Temkin isotherms fitted to the experimental data. Thermodynamic studies revealed that the adsorption process was spontaneous, as indicated by negative Gibbs free energy (ΔG°) values. The enthalpy change (ΔH°) was also negative, suggesting that the adsorption process was exothermic. The positive entropy change (ΔS°) indicated an increase in randomness at the solid-liquid interface during adsorption. From the study, CNC-Fe3O4NP-CD presented a highly effective, sustainable, and reusable adsorbent for Cr(VI)