Removal of phosphate from aqueous solution using MgO-modified magnetic biochar derived from anaerobic digestion residue

• Published in: Journal of environmental management 2019-11, Vol.250, p.109438-109438, Article 109438
• Main Authors: Liu, Jiwei, Jiang, Jianguo, Aihemaiti, Aikelaimu, Meng, Yuan, Yang, Meng, Xu, Yiwen, Gao, Yuchen, Zou, Quan, Chen, Xuejing
• Format: Article
• Language: English
• Subjects: Adsorption; Anaerobic digestion residue; MgO-Modified magnetic biochar; Phosphate; Precipitation
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.109438

A novel MgO-modified magnetic biochar (MgO@MBC) was made by chemical co-precipitation of Mg2+/Fe3+ on anaerobic digestion residue (ADR) and subsequently pyrolyzing at different temperatures. MgO@MBC was used for phosphate recovery from aqueous solution. The physicochemical properties of MgO@MBC were comprehensively investigated using TEM-EDS, FT-IR, XRD, VSM, N2 adsorption-desorption and TGA. Results showed that MgO/γ-Fe2O3 nanoparticles were successfully deposited onto the surface of BC. The effects of reaction temperature, initial solution pH, MgO@MBC dosage, coexisting anions and phosphate concentration on the removal of phosphate by MgO@MBC were researched. Additionally, the adsorption process of phosphate onto MgO@MBC was well described by the pseudo second-order and pseudo first-order models, which indicated a chemisorption and physisorption process. Besides, the maximum adsorption capacity of MgO@MBC for phosphate by the Langmuir model were 149.25 mg/g at 25 °C. Moreover, the thermodynamic study suggested that the adsorption of phosphate onto MgO@MBC was a spontaneous and endothermic process. The adsorption mechanisms including physical absorption, surface electrostatic attraction, surface complexation and precipitation were revealed. It could be concluded that MgO@MBC exhibited high removal efficiency of phosphate and excellent magnetic property for the recovery. MgO@MBC could be utilized as a magnetically recoverable adsorbent to realize phosphate recovery and MgO@MBC after the adsorpion of phosphate could be applied in agricultural production as a fertilizer. [Display omitted] •An efficient and low-cost MgO@MBC composite for phosphate recovery was made.•Nanosized MgO and γ-Fe2O3 were doped on the surface of biochar derived from ARD.•Phosphate adsorption was largely affected by various operating parameters.•Electrostatic attraction, complexation and precipitation were the removal mechanism.