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To date, highly toxic heavy metal ions from wastewater seriously deteriorate the aquatic environment safety. This study proposes an adsorbent that can be adopted to remove heavy metal ions by combining environmentally friendly cellulose nanofibers (CNFs), sodium alginate (SA), and amino-rich polyethyleneimine using a ferric chloride- and glutaraldehyde-mediated crosslinking process and yielding a porous hollow bead (CS-Fe@PEI). The bead has a hollow porous structure according to SEM and a high nitrogen content of 13.85 wt% with numerous active adsorption sites, which are beneficial to the adsorption of heavy metal ions. Chromium was chosen as the main model pollutant for batch adsorption experiments. CS-Fe@PEI has excellent adsorption capacity of 526.32 mg/g for Cr(VI) at 298 K, which conforms with the Langmuir isotherm and pseudo-second-order model. The stable hollow structure allowed the regeneration of the CS-Fe@PEI beads for more than six cycles after Cr(VI) adsorption. According to FT-IR, Zeta, and XPS analyses, the beads effectively adsorbed the pollutants by electrostatic interaction, reducing the hypertoxic Cr(VI) to Cr(III). Furthermore, the beads also possessed a superior adsorption capacity for heavy metal cations (Cu(II), Cd(II), Ni(II), and Pb(II)). These results demonstrated that the fabricated CS-Fe@PEI beads were an efficient and reusable adsorbent, with a high potential for removing heavy metal ions from industrial wastewater. [ABSTRACT FROM AUTHOR]

Amino-functionalized monodisperse polymeric microspheres have great significance in water remediation. Herein, polypyrrole (PPy)-modified silica-coated magnetic monodispersed emulsion sphere (MES) microspheres (MES@Fe3O4@SiO2-PPy, MFSP) were successfully prepared via in situ polymerization for the adsorption of hexavalent chromium in an aqueous solution. The magnetism of MFSP enabled fast separation under an applied magnetic field. The results showed that MFSP exhibited outstanding adsorption for Cr(VI) (301.2 mg g−1 at pH 2.0), which followed the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the MFSP can be reused in the adsorption–desorption cycle by simple elution, and the removal rate of Cr(VI) by MFSP remained above 91% after five consecutive cycles. Combined with XPS, EDS, and Zeta potential measurement for adsorption mechanism analysis, it was concluded that the removal of Cr(VI) could be attributed to both adsorption and reduction. The combination of good adsorption performance and magnetic separation makes MFSP a promising candidate for the removal of low-concentration metal ions. [ABSTRACT FROM AUTHOR]

• MAGC has good adsorption capacity for heavy metal ions and anionic dyes. • The maximum adsorption capacity of MAGC for Cr(VI) is 537.63 mg g−1. • MAGC reached equilibrium within 30 min and facile separation less than 25 s. • MAGC has good reusability performance for low or high Cr(VI) concentrations. Background: Biomass materials are currently attracting more research interests as pollutant adsorbent attributed to rich sources, low cost, non-toxicity, biodegradability and easy modification. Methods: Herein, a glucose-based carbon material (GC) was fabricated via hydrothermal method and formed pores materials by activation using KOH. Then the amino modified magnetic glucose-based carbon composite (MAGC) was prepared by the co-precipitation method and followed the simple cross-linking reaction. Significant Findings: MAGC had a high nitrogen content of 10.89 wt.% with many active adsorption sites and the magnetic separation process of MAGC was completed within 25 s. The adsorption experiments indicated the superior adsorption capacity of MAGC for water pollutants (several heavy metal ions and anionic dyes). Cr(VI) was selected as the model pollutant, the maximum adsorption capacity (Q max) of MAGC was 537.63 mg g−1 at pH 2 and 25 °C, which followed the pseudo-second-order model and Langmuir isotherm model. Low concentration (1 mg L−1) cyclic adsorption demonstrated that after 40 cycles without regeneration, the Cr(VI) concentration remained the below 0.05 mg L−1 in 30 min, which was the safe level of drinking water specified by WHO. This design of biomass-based carbon composites may provide a promising absorbent for efficient removal of water pollutants. [Display omitted] [ABSTRACT FROM AUTHOR]

• AF-CMS with high nitrogen loading of 25.0 wt.% was prepared. • AF-CMS could uptake methyl orange up to 1487.29 mg g−1 with high reusability. • AF-CMS displayed high removal efficiency and selectivity towards anionic dyes. • AF-CMS reached equilibrium within 30 min in adsorption process. Synthesis of biomass-based carbonaceous adsorbents with high adsorption performance, reusability, environmental-friendliness as well as low cost for water treatment remains a challenge. In this study, a glucose-based amine-functionalized carbon microsphere (AF-CMS) was synthesized via hydrothermal method and amine functional modification for the removal of organic dye. The results of materials characterization demonstrated an efficient amine functionalization of AF-CMS with a high nitrogen loading of 25.0 wt.% and strong positive charge under acidic conditions. Batch adsorption studies showed that the maximum adsorption capacities of AF-CMS for methyl orange (MO) and tartrazine (TTZ) were up to 1487.29 and 699.30 mg g−1, and the adsorption equilibrium was reached within 30 min with the 500 mg L−1 of dye solution. It could also quickly and completely capture dye molecule within 8 min for the TTZ dye solution of 100 mg L−1. The adsorption data of AF-CMS on anionic dyes was correlated with the pseudo-second-order kinetic and the Langmuir isotherm model. The adsorption capacity of AF-CMS for MO and TTZ dye still reached 1234.55 mg g−1 (83.01% of Q max) and 618.65 mg g−1 (88.47% of Q max), respectively, after five cycles of regeneration. More importantly, superior adsorption selectivity was demonstrated by the investigation of mixture of anionic dye and cation dye. Comprehensive analysis revealed that the good adsorption performance of AF-CMS was contributed to the strong electrostatic interaction between dye molecular and amine groups. Based on its simple preparation, low cost and excellent adsorption properties, the AF-CMS possesses a promising candidate for separating organic dyes from wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]