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In order to reduce the environmental hazards of red mud (RM) and realize its resource utilization, in this study, RM-based iron-carbon micro-electrolysis material (RM-MEM) were prepared by a carbothermal reduction process using RM as raw material. The influence of the preparation conditions on the phase transformation and structural characteristics of the RM-MEM were investigated during the reduction process. The ability of RM-MEM to remove organic pollutants from wastewater was evaluated. The results showed that RM-MEM prepared at a reduction temperature of 1100 °C, a reduction time of 50 min and a coal dosage of 50% had the best removal effect for the degradation of methylene blue (MB). When the initial MB concentration was 20 mg L−1, the amount of RM-MEM material was 4 g L−1, the initial pH was 7, and the degradation efficiency reached 99.75% after 60 min. When RM-MEM is split into carbon free and iron free parts for use, the degradation effect becomes worse. Compared to other materials, RM-MEM has lower cost and better degradation. X-ray diffraction (XRD) analysis showed that hematite was transformed to zero-valent iron with the increase in the roasting temperature. Scanning electron microscopy (SEM) and energy spectroscopy (EDS) analysis showed that micron-sized ZVI particles were formed in the RM-MEM, and increasing the carbon thermal reduction temperature was beneficial to the growth of zero-valent iron particles. [Display omitted] • Waste-derived iron carbon micro-electrocatalyst by carbon thermal reduction method. • Iron carbon micro-electrocatalyst shows high efficiency in the degradation of MB. • Iron carbon micro-electrocatalyst shows the potential for practical application. [ABSTRACT FROM AUTHOR]

The manganese is successfully induced as a "bridge joint" to fabricate a new adsorbent (CNC–Mn-PEI) connecting cellulose nanocrystal (CNC) and polyethyleneimine (PEI) respectively. It was used to remove As (III) from waste water. It has been proved that the incompact CNC and PEI were successfully connected by Mn ions, which induced the formation of O–Mn–O bonds and the removal efficiency is maintained in the broad pH range of 4–8, even with the influence of NO 3 − and CO 3 2−. The CNC–Mn-PEI was characterized by Brunauer–Emmett–Telley (BET) method and the results showed that the nanoparticle of the specific surface area was 106.5753 m2/g, it has a significant improvement, compared with CNC–Mn-DW (0.1918 m2/g). The isotherm and kinetic parameters of arsenic removal on CNC–Mn-PEI were well-fitted by the Langmuir and pseudo-second-order models. The maximum adsorption capacities toward As (III) was 78.02 mg/g. After seven regeneration cycles, the removal of As (III) by the adsorbent decreased from 80.78% to 68.2%. Additionally, the hypothetical adsorption mechanism of "bridge joint" effect was established by FTIR and XPS, which provided the three activated sites from CNC–Mn-PEI can improve the arsenic removal efficiency, and providing a new stratagem for the arsenic pollution treatment. [Display omitted] • The introduction of polyethyleneimine can effectively organize the forces between the molecular chains of manganese-based cellulose materials. • The removal efficiency of manganese-based cellulose materials was greatly enhanced with the introduction of polyethyleneimine for arsenite (III) removal. • The "bridging effect" of Mn was confirmed by inducing a large amount of the activated sites. [ABSTRACT FROM AUTHOR]