Process And Mechanism Of Indirect Mineralization Of CO₂ By Carbide Slag With Amino Acid Synergy

In the context of "Peak carbon dioxide emission and Carbon neutrality",CO2 Capture,Utilization and Storage technology is an important technical way to achieve the "double carbon" target on schedule,among which indirect mineralization CO2 technology is the most mature carbon reduction technology in research and industrial application.Amino acid is one of the most common CO2 absorbers in the chemical absorption method.Carbide slag is a kind of highly alkaline calcium-based industrial solid waste,which has a good application prospect in mineralized CO2 sequestration.Indirect mineralization of CO2 using Carbide slag can not only realize the comprehensive utilization of industrial solid waste resources and CO2 emission reduction,but also has good industrial feasibility and theoretical research.This thesis addresses the problems of difficult activation leaching of calcium and magnesium,low CO2 absorption efficiency,high energy consumption and slow kinetics in the indirect mineralization of CO2 from industrial solid waste,proposes a technical route to sequester CO2 by indirect mineralization of calcium and magnesium with amino acids in collaboration with Carbide slag,elucidates the mechanism of amino acids to enhance calcium leaching efficiency,and explores the effect of the integration of calcium precipitation and CO2 absorption on the mechanism of CO2 absorption by amino acids.The enhanced effect of amino acid-enhanced CO2 uptake on mineralization efficiency was revealed,and the cyclic performance of amino acid self-help regeneration in indirect mineralization was further investigated.The main studies are as follows.(1)The effect of indirect mineralization of CO2 from calcium carbide slag synergized with glycine was investigated.The results showed that glycine formed a five-membered ring water-soluble chelate with calcium ions through chelation to enhance the dissolved leaching of Ca from calcium in carbide slag.The Ca leaching concentration was 14854 mg/L at a Gly concentration of 1 mol/L.In the mineralization stage,glycine can recycle CO2 absorption in the highly alkaline leaching solution to enhance the CO2 absorption capacity.The synergistic effect between CO2 absorption and Ca precipitation integration reaction during the mineralization reaction accelerated the reaction rate and enhanced the mineralization efficiency to 93%.During the indirect mineralization process glycine is able to regenerate itself using pH swing,and can sequester CO2 in coordination with carbide slag cycle mineralization.During each cycle of mineralization,pH and Ca extraction and mineralization efficiency remain constant,and the mineralization products are all vaterite phase CaCO3,and the cycle process operates stably.(2)To investigate the effect of amino acid molecular structure on the process of indirect mineralization to sequester CO2,five representative amino acids with functional groups amino and carboxyl in the side chain structure were selected during the experiment The results showed that the carboxyl and amino groups in the molecular structure of amino acids provide coordination structures,and form double or triple coordination structure complexes with Ca,and amino acids can enhance the leaching effect of calcium ions when leaching Ca from carbide slag,and the leaching efficiency of various amino acids on calcium is between 40～50%when the concentration of amino acids is 0.5 mol/L.The functional groups in the side chain structure have a great influence on the mineralization efficiency and CO2 absorption during the mineralization of amino acid leaching solution.When the side chain structure contains amino groups,it can enhance the mineralization efficiency and CO2 absorption capacity,for example,the mineralization efficiency of lysine leaching solution is 97%.Amino acids play multiple effects in the indirect mineralization process,as calcium leaching ligands in the leaching stage to enhance Ca dissolution leaching,as CO2 absorbers in the mineralization stage to enhance CO2 absorption and improve mass transfer efficiency,and as pH buffers to provide suitable pH values for the whole reaction system.