Pioneering nanobiosorbent of doped cellulose-gelatin hydrogel into carbon quantum dots and magnesium ferrite for effective removal of Cr(VI)

Hexavalent chromium is the most stable and predominant form with high toxic effects on various environments including water and wastewater. Therefore, removal of low Cr(VI) concentration levels from water is a target with major concerns. To address this issue, a novel nanobiosorbent was generated via a facile microwave synthesis approach (<20 min). The aimed material was assembled from direct impregnation of cellulose-gelatin hydrogel (C-GHg) with carbon quantum dots (CODs) and magnesium ferrite (MgFe₂O₄) to form C-GHg@CQDs@MgFe₂O₄. This was confirmed in the range 10.10 ± 0.09 nm and 28.58 ± 0.17 nm based on the TEM analysis with surface area (270.03 m² g⁻¹) and negatively charged surface (−8.3 mV) according to the zeta potential analysis. Besides, several active functional groups were confirmed from the FT-IR investigation. The applicability of C-GHg@CQDs@MgFe₂O₄ in capturing Cr(VI) was optimized by numerous controlling parameters providing 93.4–96.9 % (5 mg/L) and 88.8–91.1 % (10 mg/L) removal by 20 mg and 50 mg nanobiosorbent in presence of 100 mg NaCl ionic strength and pH 2.0. Linear and nonlinear kinetic models concluded excellent suitability of linear PSO and Elovich models to account for Cr(VI) adsorption behavior onto C-GHg@CQDs@MgFe₂O₄. Also, Cr(VI) uptake was best demonstrated by the Langmuir and Fritz–Schlunder isotherms. C-GHg@CQDs@MgFe₂O₄ was regenerated after its initial use and found highly stable after five regenerations. The removed Cr(VI) from polluted sea, waste and tap water matrices by C-GHg@CQDs@MgFe₂O₄ affirmed excellent superiority with the achievement of high removal efficiency (>91.0 %). Finally, the developed and investigated C-GHg@CQDs@MgFe₂O₄ displayed excellent behaviors to consider it as a promising sustainable, regenerable, low-cost and efficient material for Cr(VI) removing from diverse aquatic systems.