Removal of potentially toxic metal by biochar derived from rendered solid residue with high content of protein and bone tissue

• Published in: Ecotoxicology and environmental safety 2021-01, Vol.208, p.111690, Article 111690
• Main Authors: Park, Jong-Hwan, Yun, Jin-Ju, Kang, Se-Won, Kim, Seong-Heon, Cho, Ju-Sik, Wang, Jim J., Seo, Dong-Cheol
• Format: Article
• Language: English
• Subjects: Adsorption; Animal carcass; Animals; Bone and Bones - chemistry; Cadmium - analysis; Char; Charcoal - chemistry; Diffusion; Ion Exchange; Proteins - chemistry; Pyrolysis; Rendering; Swine; Temperature; Waste Products - analysis; Waste Water - chemistry; Water Pollutants, Chemical - analysis
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2020.111690

The purpose of this study was to produce rendering animal carcass residue char (RACR-C) by pyrolyzing the solid residues of low-recyclable rendered pig carcasses and to evaluate their cadmium (Cd) adsorption characteristics and mechanisms. As the pyrolysis temperature increased, the inorganic content of RACR-C increased, while the carbon content decreased. In particular, the surface structure and chemistry of RACR-Cs prepared at different pyrolysis temperatures were well described by SEM-EDS, XRD, XRF, TGA, and FTIR. The Cd adsorption characteristics of RACR-C were in good agreement with the Langmuir isotherm and pseudo-second-order models, and the Cd adsorption capacities of RACR-Cs prepared at various pyrolysis temperatures were in the order of RACR-C500 (73.5 mg/g)> RACR-C600 (53.8 mg/g)> RACR-C400 (41.5 mg/g) " RACR-C250 (15.9 mg/g). The intraparticle diffusion model suggested that the adsorption of Cd by RACR-C is greatly influenced by internal diffusion as well as external boundary. Since the Cd adsorption capacity of RACR-C is greatly influenced by the initial dosage, pH, and co-existing metals, it is necessary to manage these influencing factors when treating wastewater containing heavy metals. Our results suggest that Cd adsorption by RACR-C is a complex adsorption phenomenon by various mechanisms such as adsorption by functional group (C˭C and C-O), precipitation of Cd-P and ion exchange reaction by exchangeable cation occurring rather than by a single specific mechanism. •Rendering animal carcass residue char (RACR-C) was prepared by pyrolysis.•The main composition of RACR-C is calcium, carbonates and phosphates.•The optimal pyrolysis temperature for Cd adsorption by RACR-C was 500 °C.•Adsorption mechanisms by RACR-C were well described by SEM-EDS, XRD, FTIR and XPS.•Cd adsorption by RACR-C is a complex phenomenon occurring by various mechanisms.