Meso-porous activated carbon from lignite waste and its application in methylene Blue adsorption and coke plant effluent treatment

Sriramoju, Santosh Kumar and Dash, Pratik Swarup and Majumdar, Saptarshi (2021) Meso-porous activated carbon from lignite waste and its application in methylene Blue adsorption and coke plant effluent treatment. Journal of Environmental Chemical Engineering, 9 (1). p. 104784. ISSN 22133437

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Abstract

Coke plant wastewater contains many toxic pollutants such as phenol, cyanide, and ammonia, etc., handling and disposal of which has a significant impact on the environment and human health. A novel adsorbent based on lignite extraction waste was prepared and its effect on the removal of simulated methylene blue, phenol and colour (ortho, para-benzo quinone) from real coking wastewater was investigated. Lignite waste (residue) after humic acid separation has a significant quantity of oxidized functional groups along with residual KOH, which makes it suitable for the preparation of activated carbon with high surface area. Since hydrothermal extraction breaks coal-mineral-pore aggregate, the separation efficiency of ash-bearing minerals improved, 11 % ash coal prepared from the residue with 81.6 % yield. Prepared activated carbon from low ash residue has a mesoporous surface (49.8 nm pore size), 0.554 cm3/g of total pore volume, and 980 m2/gram BET surface area. The adsorption kinetics followed pseudo-second order (R2 = 0.984) for methylene blue, pseudo-second-order (R2 = 0.978) for phenol, and pseudo-first-order (R2 = 0.935) for colour adsorption. Adsorption isotherm at equilibrium shows a maximum adsorption capacity of 120 mg/g for methylene blue, 20.49 mg/g for phenol and 588.23 PtCo/g for colour. The adsorption isotherm was in good agreement with Langmuir isotherm (R2 = 0.989-0.994) compared to Freundlich model (R2 = 0.924-0.982). The presence of negatively charged surface favours the uptake of cationic groups. Apart from phenol and colour, the adsorbent can remove total organic carbon (TOC) by 93.6 % and thiocyanide by 6.7 %. Adsorbent reutilization studies show that, the regenerated adsorbent by thermal treatment can be used for 3 cycles.

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