Cu–Fe embedded cross-linked 3D hydrogel for enhanced reductive removal of Cr(VI): Characterization, performance, and mechanisms

• Published in: Chemosphere (Oxford) 2021-10, Vol.280, p.130663-130663, Article 130663
• Main Authors: Wang, Yin, Lin, Naipeng, Gong, Yishu, Wang, Ruotong, Zhang, Xiaodong
• Format: Article
• Language: English
• Subjects: 3D hybrid hydrogel; Cr(VI); Fe–Cu bimetallic Composite; Reduction activity; Stability
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.130663

Porous hydrogel, as a high-efficiency adsorbent for heavy metals, suffers the drawbacks of the use of expensive and toxic reagents during the process of preparation, further limiting its application ranges. Besides, the heavy metals couldn't be transformed into nontoxic species, which leads to the environmental pollution risk. Herein, a three-dimensionally (3D) structured Cu–Fe embedded cross-linked cellulose hydrogel (nFeCu-CH) was innovatively fabricated by a novel self-assembly and in-situ reduction method, which exhibited exceptionally enhanced adsorption-reduction property towards Cr(VI) wastewater. The results of degradation experiment exhibited that the removal reaction followed Langmuir-Hinshelwood first order kinetic model and the degradation rate constant decreased with solution pH and initial Cr(VI) concentration, while increased with nFeCu-CH dosage and temperature. Regeneration studies demonstrated that more than 88% of Cr(VI) was removed by nFeCu-CH even after five times of cycling. nFeCu-CH exhibited excellent reductive activity, which had a close connection with the superiority of 3D crosslinked architectures and bimetallic synergistic effect. And 97.1% of Cr(VI) could be removed when nFeCu-CH dosage was 9.5 g/L, pH was 5, initial concentration of Cr(VI) was 20 mg/L and temperature was 303 K. Combined with cellulose hydrogel not only could provide additional active sites, but also could restrain the crystallite growth and agglomeration of nano-metallic particles, leading to the promotion of Cr(VI) removal. In addition, coating with Cu facilitated the generation and transformation of electrons according to the continuous redox cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I), leading to the further improvement of the reductivity of nFeCu-CH. Multiple interaction mechanisms including adsorption, reduction and co-precipitation between nFeCu-CH and Cr(VI) were realized. The current work suggested that nFeCu-CH with highly reactive sites, excellent stability and recyclability was considered as an potential material for remediation of Cr(VI) contaminated wastewater. [Display omitted] •Cu–Fe embedded crosslinked 3D hydrogel was synthesized by in-situ reduction method.•nFeCu-CH showed highly Cr(VI) reductive reactivity, stability and recyclability.•Synergistic effect of CH, Fe and Cu are responsible to the excellent performance.•The redox cycles of Fe(III)/Fe(II) and Cu(II)/Cu(I) are involved in the reaction.