Effects of physicochemical properties of biochar derived from spent coffee grounds and commercial activated carbon on adsorption behavior and mechanisms of strontium ions (Sr2+)

• Published in: Environmental science and pollution research international 2021-08, Vol.28 (30), p.40623-40632
• Main Authors: Shin, Jaegwan, Lee, Sang-Ho, Kim, Sangwon, Ochir, Duuriimaa, Park, Yongeun, Kim, Jihye, Lee, Yong-Gu, Chon, Kangmin
• Format: Article
• Language: English
• Subjects: Activated carbon; Adsorption; Aquatic Pollution; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Charcoal; Chemical and Biological Process Techniques and Tools for Pollution Prevention and Sustainability; Chemisorption; Coffee; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Functional groups; Isotherms; Kinetic equations; Physical; Physicochemical properties; Specific surface; Strontium; Surface area; Surface chemistry; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-020-10095-6

This study examined differences in the adsorption isotherms, kinetic equations, and thermodynamics of Sr 2+ by biochar from spent coffee grounds (SCG) and powdered activated carbon (PAC). The specific surface area (957.6 m 2 /g) and pore volume (0.676 cm 3 /g) of PAC were much greater than those of SCG biochar (specific surface area = 11.0 m 2 /g, pore volume = 0.009 cm 3 /g). However, SCG biochar showed a higher maximum adsorption capacity of Sr 2+ ( Q max  = 51.81 mg/g) compared with PAC ( Q max  = 32.79 mg/g) due to its abundance of O-containing functional groups. The negligible removal efficiencies of Sr 2+ by SCG biochar and PAC under acidic conditions (pH = 1.0–3.0) are evidence that the electrostatic repulsion might hinder severely the adsorption of Sr 2+ by the carbonaceous adsorbents. The higher R 2 values of the pseudo-second-order model ( R 2  ≥ 0.999) compared with the pseudo-first-order model ( R 2  ≥ 0.815) suggest that chemisorption governed the removal of Sr 2+ using SCG biochar and PAC. Furthermore, the better description of the adsorption behavior of Sr 2+ by the Langmuir isotherm model ( R 2  ≥ 0.994) than the Freundlich isotherm model ( R 2  ≥ 0.982) supports the assumption that the monolayer adsorption played critical roles in the removal of Sr 2+ using SCG biochar and PAC. The thermodynamic studies revealed that adsorption of Sr 2+ onto SCG biochar and PAC was endothermic and happened spontaneously. Despite the significant inhibitory effects of DOM, SCG biochar exhibited the higher removal efficiencies of Sr 2+ compared with PAC. Hence, SCG biochar could be considered as an alternative to PAC for the removal of Sr 2+ from aqueous solutions.