Abstract
Hydrous ferric oxide (HFO) is most effective with high treatment capacity on arsenate [As(V)] sorption although its transformation and aggregation nature need further improvement. Here, HFO nanoparticles with carboxymethyl cellulose (CMC) or starch as modifier was synthesized for the purpose of stability improvement and As(V) removal from water. Comparatively, CMC might be the optimum stabilizer for HFO nanoparticles because of more effective physical and chemical stability. The large-pore structure, high surface specific area, and the non-aggregated nature of CMC-HFO lead to increased adsorption sites, and thus high adsorption capacities of As(V) without pre-treatment (355 mg·g−1), which is much greater than those reported in previous studies. Second-order equation and dual-mode isotherm model could be successfully used to interpret the sorption kinetics and isotherms of As(V), respectively. FTIR, XPS and XRD analyses suggested that precipitation and surface complexation were primary mechanisms for As(V) removal by CMC modified HFO nanoparticles. A surface complexation model (SCM) was used to simulate As adsorption over pH 2.5–10.4. The predominant adsorbed arsenate species were modeled as bidentate binuclear surface complexes at low pH and as monodentate complexes at high pH. The immobilized arsenic remained stable when aging for 270 d at room temperature.
Highlights
Starch and carboxymethyl cellulose (CMC) are both low-cost and environmentally friendly, and they share similar macromolecular skeletons
After 24 h of standing, the average hydrodynamic diameters of the bare hydrous ferric oxide (HFO) particles and those modified with 0.064% CMC and 0.12% starch were 1605, 216, and 283 nm, respectively
Hydrous Fe (III) oxides could convert to the crystalline Fe (III) oxides gradually[33], but this did not happen for the CMC-modified nanoparticles
Summary
Starch and carboxymethyl cellulose (CMC) are both low-cost and environmentally friendly, and they share similar macromolecular skeletons. CMC carries carboxylate and hydroxyl groups[19] They have been used as stabilizer materials in preparing ZVI, FeS, Fe-Mn oxides, or magnetite nanoparticles for heavy metals and organic contaminants[21,22,29,30,31]. It was reported the primary mechanism for binding CMC to Fe2+ was bidentate bridging while starch worked through steric stabilization[19]. In order to examine the effective removal of arsenate [As(V)] from aqueous solution, a series of HFO nanoparticles modified with various concentrations of starch or CMC were synthesized. The objectives were to (I) characterize the modified HFO nanoparticles and elucidate the stability mechanism; (II) test the effects of type and concentration of modifier, reaction time and solution pH on the effectiveness of As(V) sorption; (III) elucidate the As sorption kinetics, isotherm, and mechanism; (IV) test the effects of nanoparticle aging on As(V) immobilization and long-term stability; and (V) examine the reusability of the regenerated modified HFO nanoparticles for subsequent cycles of As(V) sorption
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
