The use of solid wastes and industrial by-products to prepare CO₂ adsorbents is an alternative to conventional reagent grade raw materials that has recently gained interest. Among waste materials, slag has a high content of silica and calcium and is the largest solid by-product from iron and steel industry, thus its use can reduce the production costs of CO₂ adsorbent materials, such as lithium silicates, which are applied in capture processes at high temperatures. Li₄SiO₄ has potential applications in post-combustion CO₂ capture as well as in H₂ production by sorption enhanced steam reforming process. In this study, Li₄SiO₄ was prepared using solid-state reaction and two iron and steel slags as SiO₂ sources to evaluate their characteristics and CO₂ capture capacities. The slag-derived lithium silicates (S1-Li₄SiO₄ and S2-Li₄SiO₄) were characterized by XRD, adsorption-desorption N₂ and SEM. Different capture tests at CO₂ partial pressures (\(P_{{{\text{CO}}_{2} }}\)) of 0.05, 0.10, 0.15 and 0.20 were performed using thermogravimetric (TG) and temperature programmed (TPC-TPDC) techniques. The kinetic parameters of the CO₂ capture process were obtained by fitting the experimental results to the Avrami–Erofeev model. Finally, the cyclic behavior of S1-Li₄SiO₄ and S2-Li₄SiO₄ was analyzed in \(P_{{{\text{CO}}_{2} }}\) of 0.2 and 0.05. XRD patterns showed that Li₄SiO₄ was the main crystal phase (60 wt%) present in S1-Li₄SiO₄ and S2-Li₄SiO₄ in addition to calcium phases such as Li₂CaSiO₄, Ca₃SiO₅ and CaO. According to the TG and TPC-TPDC tests, the derived lithium silicates showed CO₂ uptake three times greater than the values recorded for Li₄SiO₄ (134 mgCO₂/g sorbent for S1-Li₄SiO₄) produced from pure reagents, at \(P_{{{\text{CO}}_{2} }}\) between 0.2 and 0.05 and 650 °C. Furthermore, these materials had kinetic constants at least one order of magnitude higher than those reported for Li₄SiO₄, at the aforementioned operating conditions. Both materials exhibited an excellent stability during 20 cycles of CO₂ adsorption/desorption. These results showed that slags can be used as silica source to produced adsorbents with better performance and stability in the CO₂ capture process at high temperature than the one of Li₄SiO₄ produced from pure reagents, at \(P_{{{\text{CO}}_{2} }}\) of 0.2–0.05.

中文翻译：

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由钢铁渣合成的硅酸锂作为高温CO 2吸附材料

使用固体废物和工业副产品制备CO ₂吸附剂是最近引起关注的常规试剂级原料的替代方法。在废料中，炉渣中二氧化硅和钙的含量高，是钢铁行业最大的固体副产物，因此其使用可以降低CO ₂吸附剂材料（如硅酸锂）的生产成本，该材料可用于在高温下捕获过程。Li ₄ SiO ₄在燃烧后的CO ₂捕集以及通过吸附增强的蒸汽重整工艺生产H _2中具有潜在的应用。在这项研究中，Li ₄ SiO ₄用固相反应和两种钢铁渣作为SiO ₂源制备了氧化铁，以评估其特性和CO ₂捕获能力。通过XRD，吸附脱附N ₂和SEM对熔渣来源的硅酸锂（S1-Li ₄ SiO ₄和S2-Li ₄ SiO ₄）进行了表征。使用热重（TG）和程序升温（TPC）在0.05、0.10、0.15和0.20的CO ₂分压（\（P _ {{{text {CO}} _ {2}}} \）下进行不同的捕获测试-TPDC）技术。CO ₂的动力学参数通过将实验结果拟合到Avrami-Erofeev模型获得捕获过程。最后，S1-Li的循环行为₄的SiO ₄和S2-栗₄的SiO ₄中进行了分析\（P _ {{{\文本{CO}} _ {2}}} \）的0.2和0.05。XRD图谱表明，除了钙相如Li ₂ CaSiO ₄，Ca ₃ SiO _5外，Li ₄ SiO ₄是S1-Li ₄ SiO ₄和S2-Li ₄ SiO ₄中存在的主要晶相（60 wt％）。和CaO。根据TG和TPC-TPDC测试，衍生的硅酸锂显示出的CO ₂吸收量是纯试剂生产的Li ₄ SiO ₄（134 mgCO ₂ / g S1-Li ₄ SiO ₄吸附剂）记录的三倍，在0.2至0.05和650°C之间的\（P _ {{{\ text {CO}} _ {2}}} \）下。此外，在上述操作条件下，这些材料的动力学常数比Li ₄ SiO ₄所报道的动力学常数高至少一个数量级。两种材料在20个CO ₂循环中均表现出出色的稳定性。吸附/解吸。这些结果表明，渣可以被用作二氧化硅源以产生吸附剂具有更好的性能和稳定性中的CO ₂在高温下比Li的一个捕获过程₄的SiO ₄从纯试剂生产的，在\（P _ {{{\文本{CO}} _ {2}}} \）为0.2-0.05。