废弃混凝土中钙离子的提取实验研究

废弃混凝土间接碳酸化封存CO2的重要一步是将Ca2+从混凝土中提取出来。论文对废弃混凝土中Ca2+的提取进行了研究,主要考察了提取溶剂、混凝土粒径、温度和固液比等对Ca2+提取过程的影响。对不同的提取溶剂进行了比较,发现HNO3作为溶剂时Ca2+提取率最高,其次为CH3COOH、HCOOH和H2SO4。减小混凝土粒径可有效提高Ca2+提取率。对粒径小于0.15 mm的混凝土,Ca2+提取率随温度升高而增大,其最佳固液比为40 g/L。粒径大于0.25 mm时,最佳固液比为20 g/L,温度的影响明显减弱。将Ca2+提取实验结果与XRD、SEM表征结合,发现废弃混凝土提取过程中SiO2惰性层的出现是限制Ca2+提取率进一步提高的重要原因。

Experimental Study of Ca~(2+) Extraction from Waste Concrete

Ca2+ extraction is an important step for sequestration of CO2 by indirect carbonation of waste concrete.Studies on the extraction of Ca2+ from waste concrete were done,and effects of extraction solvent,particle size of waste concrete,temperature and solid-liquid ratio upon Ca2+ extraction were investigated.Different extraction solvents were compared,and the extraction rate was highest with HNO3 as solvent,followed by CH2COOH,HCOOH and H2SO4.Ca2+ extraction rate was effectively improved by reducing the particle size.For concrete with particle size less than 0.15mm,Ca2+ extraction rate increased with the increasing temperature,and the optimum solid-liquid ratio was 40 g/L.The optimum solid-liquid ratio was 20 g/L when the particle size was greater than 0.25 mm,while the effect of temperature was significantly weakened.Combining the experimental result and XRD,SEM characterization,it was found that a SiO2 inert layer formed during the extraction process would hinder the further extraction of Ca2+.