Fabrication of robust CaO-based sorbent via entire utilization of MSW incineration bottom ash for CO2 capture

Abstract

CO2 capture using CaO-based sorbent is a promising and effective CO2 mitigation strategy due to its high theoretical capacity of CO2 adsorption and potential use in large scale. The preparation of waste-derived CaO-based CO2 sorbents has received extensive interests due to its economic feasibility via waste recycling. In this work, the development of a novel robust CaO-based sorbent via the entire utilization of municipal solid waste incineration (MSWI) bottom ash (BA) was reported. Specifically, residues from the extraction of CaO from BA were added back to the extracted CaO after thermal passivation. The results showed that the addition of BA residue-derived stabilizer (BAS) promoted the homogeneous dispersion of CaO and increased the specific surface area (17.66 m2/g) of the BAS/CaO sorbents and pores in the range of 20–100 nm. Meanwhile, the small amounts of Al2O3 and SiO2 in the Ca-Si-Al-O species of BAS reacted with CaO to form Ca12Al14O33 and Ca2SiO4 during cyclic carbonation/calcination, which was beneficial to alleviate the aggregation and sintering between CaO particles and maintain porous structure of sorbents. In addition, the CO2 uptake exhibited a volcano-type variation with the increase of BAS additive amount and carbonation temperature, where the optimum carbonation temperature for BAS(20 wt%)/CaO sorbents was 700 °C. Among the various sorbents, the BAS(20 wt%)/CaO sorbent (BAS/CaO = 2/8) exhibited the most superior CO2 uptake of 0.14 gCO2/gsorbent after 20 cycles. This study provides a promising method to achieve a cost-effective CO2 capture candidate with enhanced capacity by completely reusing solid wastes, which eliminates the disposal of secondary residues that was rarely considered in previous studies.