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A novel magnetic Fe3O4@SiO2@Bi2O2CO3/rGO composite comprising of uniform core-shell-structured Fe3O4@SiO2@Bi2O2CO3 microspheres mounted on reduced graphene oxide (rGO) sheets was successfully fabricated by using a facile hydrothermal method. The adsorption–desorption isotherm of Fe3O4@SiO2@Bi2O2CO3/rGO belonged to type IV with an H4-type hysteresis loop. The specific surface areas and magnetization saturation value (Ms) of Fe3O4@SiO2@Bi2O2CO3/rGO (x = 0.15 g) were 102.12 m2/g and 25.4 emu/g, respectively. Fe3O4@SiO2@Bi2O2CO3/rGO (x = 0.15 g) exhibited remarkable photocatalytic degradation activity and mineralization effect for MO and decolorization performance for the mixed solution of MO, Rh B, and MB. MO degradation by Fe3O4@SiO2@Bi2O2CO3/rGO conformed to a first-order kinetic reaction, and the corresponding kapp value was 0.05553 min−1. A suitable amount of rGO in Fe3O4@SiO2@Bi2O2CO3/rGO could decrease the energy band gap, inhibit the recombination of photo-induced electron/hole (e−/h+) pair, and broaden and enhance the response of the catalyst to visible light, thereby enhancing the visible-light catalytic degradation of organic dyes. The active species produced in the photocatalysis included •O2−, •OH, and h+, with •O2− being the dominant active species. The as-prepared photocatalyst also showed excellent magnetic separation performance and stability. Results show that the as-prepared Fe3O4@SiO2@Bi2O2CO3/rGO composite is a promising photocatalyst with considerable application potential in organic dyes removal. [ABSTRACT FROM AUTHOR]

The adsorption characteristic and mechanism of poly(N1,N1,N3,N3-tetraallylpropane-1,3-diaminium chloride) (PTAPDAC) toward Cr(VI) ions were systematically investigated. Results showed that the removal efficiency of PTAPDAC toward Cr(VI) could reach above 98% at pH = 3–6. The equilibrium data of Cr(VI) adsorbed by PTAPDAC fitted the Langmuir model well, and the maximum sorption capacity deduced from the Langmuir model at 293 K was 273.17 mg g−1. The adsorption of PTAPDAC toward Cr(VI) was rapid and reached equilibrium within 60 min, and the adsorption kinetic process was relevant to the pseudo-second-order kinetic model. Moreover, the activation energy Ea was calculated as −22.505 kJ mol−1. The adsorption processes were spontaneous and exothermic driven by an increase in entropy, which involved electrostatic attraction, ion exchange, and redox reactions. The X-ray photoelectron spectroscopy analysis revealed that approximately 64.5% of Cr(VI) reduced to be Cr(III), and 24.29% of –C–NH+ deprotonated. The combination of reduced Cr(III) with tertiary amine groups resulted in a positively charged tertiary amine group, which further promoted Cr(VI) adsorption, thereby increasing the adsorption capacity of PTAPDAC toward Cr(VI). Therefore, PTAPDAC has a broad application prospect in removing Cr(VI) ions in wastewater. [ABSTRACT FROM AUTHOR]

A two-component material (Fe3O4@CaSiO3) with an Fe3O4 magnetite core and layered porous CaSiO3 shell from calcium nitrate and sodium silicate was synthesized by precipitation. The structure, morphology, magnetic properties, and composition of the Fe3O4@CaSiO3 composite were characterized in detail, and its adsorption performance, adsorption kinetics, and recyclability for Cu2+, Ni2+, and Cr3+ adsorption were studied. The Fe3O4@CaSiO3 composite has a 2D core–layer architecture with a cotton-like morphology, specific surface area of 41.56 m2/g, pore size of 16 nm, and pore volume of 0.25 cm3/g. The measured magnetization saturation values of the magnetic composite were 57.1 emu/g. Data of the adsorption of Cu2+, Ni2+, and Cr3+ by Fe3O4@CaSiO3 fitted the Redlich–Peterson and pseudo-second-order models well, and all adsorption processes reached equilibrium within 150 min. The maximum adsorption capacities of Fe3O4@CaSiO3 toward Cu2+, Ni2+, and Cr3+ were 427.10, 391.59, and 371.39 mg/g at an initial concentration of 225 mg/L and a temperature of 293 K according to the fitted curve with the Redlich–Peterson model, respectively. All adsorption were spontaneous endothermic processes featuring an entropy increase, including physisorption, chemisorption, and ion exchange; among these process, chemisorption was the primary mechanism. Fe3O4@CaSiO3 exhibited excellent adsorption, regeneration, and magnetic separation performance, thereby demonstrating its potential applicability to removing heavy metal ions. [ABSTRACT FROM AUTHOR]