Search

In this work, chitosan-grafted-poly(acrylic acid) (CS-g-PAA) was synthesized for use as a Co2+ adsorbent and circularly utilized as a peroxymonosulfate (PMS) activator in the degradation of rhodamine B (RhB) dye. CS-g-PAA demonstrated 3.7 times higher adsorption capacity toward Co2+ than pristine chitosan. The impact of the adsorption conditions was evaluated. The pseudo-second-order kinetic model and the Langmuir isotherm model best described the adsorption process. Under optimum conditions, the adsorption capacity of CS-g-PAA for Co2+ was 212 mg/g. The Co2+-adsorbed CS-g-PAA hydrogel was further utilized in the RhB degradation process. The effects of catalyst dosage, initial RhB concentration, pH, and the coexistence of anions on the degradation of RhB were studied. The hydrogel catalyst could remove 98 % of RhB within 5 min, at a degradation rate of 0.624 per min. Electron paramagnetic resonance (EPR) analysis and the radical scavenger experiment suggested that SO 4 •−, HO•, 1O 2 , and O 2 •− were involved in the degradation. Furthermore, when tested in various water systems, high degradation efficiencies of 98 % were attained after 20 min. The hydrogel catalyst performed excellent degradation over ten cycles without any chemical recovery processes. Moreover, high degradation efficiencies were observed between 95 % and 98 % when tested with other dyes. [ABSTRACT FROM AUTHOR]

Using agrochemicals are considered as an anthropogenic source of heavy metal contamination in water, and ecofriendly remediation tools for removal is desired. Here, we demonstrate material circulation by converting SiO 2 extracted from agrowaste: rice husk ash, into an easily collectable adsorbent: BEA zeolite/Fe 3 O 4 composite, through dry-gel conversion technique. In addition, the synthesized BEA zeolite/Fe 3 O 4 composite was tested for removal of heavy metals for the first time. Instrumental analyses confirmed that incorporated Fe 3 O 4 particles inside BEA zeolites showed no severe effects on its morphologies. Pseudo-second order kinetic and Langmuir isotherm models were found best described the adsorption of three typical toxic heavy metals: Pb(II), Cu(II), Zn(II). Moderate adsorption capacities of 0.675, 0.310, and 0.308 mmol/g for Pb(II), Cu(II), and Zn(II), respectively, following the selectivity order: Pb(II) > Cu(II) ≈ Zn(II) were obtained. The composite adsorbent exhibits magnetic collectability, reusability and stability, indicating its practicality for removal of heavy metals from water. [Display omitted] • First try on heavy metal removal using magnetic zeolite made by dry-gel conversion. • Agrowaste-based-magnetic zeolite used to purify agrochemical-based heavy metals. • The magnetic zeolite was a composite of BEA zeolite with Si/Al∼20 and Fe 3 O 4. • A reusable and magnetically collectable adsorbent for Pb, Cu, and Zn was developed. • The adsorption capacities were 0.675, 0.310, and 0.308 mmol/g for Pb, Cu, and Zn. [ABSTRACT FROM AUTHOR]