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This study discussed the mechanism of Fe-modified biochar (FeBC) derived from rice straw biochar (BC) as an adsorbent for removing Cr(VI) from aqueous solution and assessed its applicability in actual industrial wastewater. The Cr(VI) removal percentage increased with the FeBC dose, which achieved a removal of 99.5% at 8.0 g/L FeBC. Increasing the solution pH from 2 to 10 slightly reduced Cr(VI) adsorption by 6.6%. Coexisting ions such as Ca2+, Na+ and Cl− inhibited the removal of Cr(VI); the removal rate decreased to 60% at their concentration of 0.25 mol/L. The adsorption isotherm and kinetics were better described by the Langmuir isotherm and pseudo-second-order kinetic models, respectively. Through scanning electron microscopy with energy dispersive X-ray, the Brunauer–Emmett–Teller method, Fourier transform infrared, X-ray diffraction and X-ray photoelectron spectroscopy, the analysis revealed that FeBC with iron oxides loaded onto its surface had more active sites than BC; the surface functional groups changed; the removal of Cr(VI) by FeBC was mainly attributed to electrostatic adsorption; the redox reaction of Cr, and Fe loaded onto BC enhanced Cr(VI) reduction process. FeBC showed a good removal performance on actual industrial wastewater with the concentration of both total Cr and Cr(VI) meeting the integrated wastewater discharge standard of China.

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Background: Developing environmentally benign and non-vanadium SCR catalysts remains a challenging task for NOx abatement. In this article, Fe-Ce catalysts including Fe-Ce(S) and Fe(S)-Ce catalysts with different molar ratios of Fe/Ce were synthesized by different precursors of active species expecting to gain high catalytic activity for the selective catalytic reduction (SCR) of NOx with NH 3 in a wide temperature range.Results: The Fe-Ce(S) catalyst exhibited better catalytic activity than the Fe(S)-Ce catalyst. The characterization results indicated the Fe-Ce(S)catalyst possessed better dispersion of active species, which would favor the contact of active sites and reactant molecules and thus enhance the catalytic performance. Moreover, higher ratios of Fe 3+ and Ce 3+ and more surface chemisorbed oxygen were observed over the Fe-Ce(S) catalyst. In addition, the Fe-Ce(S) catalyst held better low-temperature redox properties and more weak acid sites.Conclusions: The precursor effect was closely related to the catalytic activity of catalysts. All of the mentioned above might be the main reasons for the superior catalytic performance of the Fe-Ce(S) catalyst, especially at low temperatures. These findings indicate that Fe-Ce(S) catalyst is a promising catalyst for the SCR reaction to replace V-W-Ti catalysts and can provide guidance for the development of environmentally benign and non-vanadium SCR catalysts.