The silica aerogels were prepared via a sol-gel technique and ambient pressure drying by using industrial solid wastes, dislodged sludges, as raw materials. A strategy was put forward to reduce the corrosion of equipment during the drying procedure. The pore structure, hydrophobicity, and thermal insulation property of the obtained samples were investigated in detail. The results show that the corrosion can be effectively avoided by using an equimolar mixture of trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) as silylation agents. At a Si:TMCS:HMDS molar ratio of 1:0.375:0.375, the silica aerogels possess a desirable pore structure with a pore volume of 3.3 ± 0.1 cm³/g and a most probable pore size of 18.5 nm, a high hydrophobicity with a water contact angle of 144.2 ± 1.1°, and a low thermal conductivity of 0.031 ± 0.001 W/(m∙K).

The slag obtained in the process of pig iron smelting has been widely used, but the variational hydration activity always is a significant factor affecting its quality. In this experiment, the laboratory simulated slag was prepared by adjusting the chemical composition and cooling method. The experiment primary characterized the structure and hydration process with different types of slag by using MAS NMR, XRD, compressive strength, ICP, SEM, and hydration heat, then obtained the influence of the composition of the network former S/A (the mass ratio of SiO₂ and Al₂O₃ in chemical composition) and amorphous phase content on its structure and hydration activity. The result shows that lowering the S/A value can reduce the degree of vitreous polymerization in the slag; reducing the S/A value of the slag can make the slag hydration time advance, and consequently, the cumulative exotherm increases, the liquid phase Ca/Si and Al/Si ionic ratio increases, and the hydration product changes from C–S–H gel to C–A–S–H gel, which ultimately leads to an increase in compressive strength. In the high S/A value slag, the formation of the trace crystal phase of gehlenite is beneficial to reduce the degree of polymerization of the amorphous.

In order to obtain low-cost and excellent adsorption materials, this paper used calcium acetate and water glass as raw materials to synthesis hydrated calcium silicate gel by precipitation method. The performance and structure of hydrated calcium silicate gel were systematically studied by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, specific surface area analyzer and scanning electron microscope. Studies have shown that, non-crystal hydrated calcium silicate gel (CSH) were successfully prepared, and the removal rate of lead ion using CSH reached more than 90%. The adsorption process is consistent with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and the limit adsorption capacity reaches 263.17 mg·g⁻¹. The acid treatment experiment proved that the adsorption capacity of lead ion using CSH was satisfactory, and the adsorption rate remained at >60% after 5 cycles. The research may provide a low-cost, high-efficiency and high stability adsorbent.

The potential possibility of blast furnace slag as a low-cost adsorbent to remove lead ions from wastewater was investigated in detail in the present work. Both single factor experiment and orthogonal experiment were performed to reveal the effect of pH, adsorption temperature, contact time and initial concentration of lead ions on the adsorption performance of pristine slag. In order to make clear the correlation between the lead ion adsorption performance and the structure of slag, solid state nuclear magnetic resonance (NMR) was conducted to reveal the network structure and X-ray fluorescence (XRF) was used to calculate the nonbridging oxygen in the network-forming tetrahedra. For the purpose of improving the adsorption performance, γ-aminopropyltriethoxysilane (APTES) was adopted to modify the slag via post-grafting method. The results show that the slag is predominately composed of SiO₂, Al₂O₃, CaO and MgO, exhibiting an amorphous network structure based on SiO₄ and AlO₄ tetrahedra. The conditions for adsorption can be optimized as follows: a pH of 7, an adsorption temperature of 60 °C, a contact time of 120 min and an initial lead ion concentration of 40 mg·L⁻¹. Under the optimal conditions, a removal rate of 99.98% and an adsorption capacity of 49.99 mg·g⁻¹ are obtained for the pristine slag. The adsorption complies with the Langmuir model thermodynamically and conforms to the pseudo-second order model kinetically. It is noted that aminopropyl-modification has considerably enhanced the removal rate of lead ions from 20.71 to 64.32% and the adsorption capacity from 29.01 to 96.48 mg·g⁻¹ since amino groups (-NH₂) are more inclined to form a complex with lead ions than hydroxyl groups due to the higher nucleophilicity of amino groups than that of hydroxyl groups. However, it is necessary to develop more low-cost modification agents in the future work.