Fe/C materials prepared by one-step calcination of acidified municipal sludge and their excellent adsorption of Cr(VI)

• Published in: Chemosphere (Oxford) 2022-10, Vol.304, p.135303-135303, Article 135303
• Main Authors: Shi, Ruixue, Liu, Tianbao, Lu, Jing, Liang, Xiangjing, Ivanets, Andrei, Yao, Junqin, Su, Xintai
• Format: Article
• Language: English
• Subjects: Acidifying and modifying; adsorption; biochar; Cr(VI) adsorption; electrostatic interactions; endothermy; Fe–C bonding; hydrochloric acid; iron; kinetics; Municipal sludge; sludge; sorption isotherms
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.135303

Biochar derived from municipal sludge can be applied to adsorption. But it usually requires activation and pickling due to the generation of impurities such as metal oxide particles, which is uneconomical. Here, a facile strategy, acidification-one-step calcination, was developed and sludge-based Fe–C materials with good Cr(VI) removal effect were obtained by regulating the amount of hydrochloric acid. The results show that the adsorption capacity of Fe/C-5 (the best sample) for Cr(VI) was 150.84 mg g−1. According to the Langmuir isotherm and pseudo-second-order kinetic model, the removal of Cr(VI) by Fe/C-5 is spontaneous and endothermic chemisorption process. In addition, Fe/C-5 has good ability to remove Cr(VI) under the interference of coexisting ions, and has good cycle stability. The removal of Cr(VI) by Fe/C-5 is considered to be synergistic process of adsorption and reduction. The Fe atoms were highly dispersed in Fe/C-5 and tightly bonded with C atoms, which not only strengthened the Cr(VI) adsorption by electrostatic attraction, but also activated the C atoms in the biochar material, so that the C atoms can reduce Cr(VI) to Cr(III) under acidic conditions. This may be due to the fact that acid pretreatment converted the iron in municipal sludge in the form of Fe–O/OH to free Fe3+ and entered the C lattice during the calcination process. In this work, Fe–C materials with excellent Cr(VI) adsorption capacity were prepared by one-step calcination method, which has important reference significance for the resource utilization of municipal sludge. [Display omitted] •Fe/C materials were prepared by one-step calcination of acidified municipal sludge.•The Fe3+ are highly dispersed in Fe/C-5 rather than in the form of cluster.•Fe/C materials removed Cr(VI) by adsorption and reduction synergistically.