标题：Steel Slag and Autoclaved Aerated Concrete Grains as Low-Cost Adsorbents to Remove Cd<sup>2+</sup> and Pb<sup>2+</sup> in Wastewater: Effects of Mixing Proportions of Grains and Liquid-to-Solid Ratio
摘要：This study investigated the applicability of industrial by-products such as steel slag (SS) and autoclaved aerated concrete (AAC) grains (<0.105, 0.105–2, 2–4.75 mm) as low-cost adsorbents for simultaneous removal of Cd<sup>2+</sup> and Pb<sup>2+</sup> in wastewater. A series of batch adsorption experiments was carried out in single and binary-metal solutions of Cd<sup>2+</sup> and Pb<sup>2+</sup> by changing the mixing proportions of SS and AAC grains. In addition, the effect of the liquid-to-solid ratio (L/S) on the removal of Cd<sup>2+</sup> and Pb<sup>2+</sup> in multi-metal solution was examined. Results showed that SS grains had a high affinity with Cd<sup>2+</sup> in the single solution, while AAC grains had an affinity with Pb<sup>2+</sup>. In the binary solution, the mixtures of SS and AAC grains removed both Cd<sup>2+</sup> and Pb<sup>2+</sup> well; especially, the tested adsorbents of SS+AAC [1:1] and SS+AAC [1:4] mixtures achieved approximately 100% removal of both metals. Based on the results in the multi-metal solutions, the metal removal % and selectivity sequence varied depending on the mixed proportions of SS and AAC grains and L/S values. It was found that the SS+AAC [1:1] mixture of SS and AAC grains showed 100% removals of Cd<sup>2+</sup>, Pb<sup>2+</sup>, Cu<sup>2+</sup>, Ni<sup>2+</sup>, and Zn<sup>2+</sup> simultaneously at L/S = 10 and 60.
