Mild Hydrothermal Synthesis of 11Å-TA from Alumina Extracted Coal Fly Ash and Its Application in Water Adsorption of Heavy Metal Ions (Cu(II) and Pb(II))

Preparation of zirconium oxide nanoparticles from rosette concentrate using two distinct and sequential techniques: hydrothermal and fusion digestion

The preparation of zirconium dioxide nanoparticles (ZrO2-NPs) as hard ceramics was accomplished from rosette zircon concentrate through two consecutive alkaline digestion reactions. The rosette zircon concentration in the Abu Khashaba area consists mainly of zircon and monazite minerals. Using different operating conditions, the hydrothermal digestion by autoclave and the conventional alkaline fusion methods was performed upon the non-magnetic concentrate of rosette in order to complete the removal of monazite firstly and to complete the purification of zircon metal secondly. All monazite content and undesirable impurities were removed by the hydrothermal method using optimal digestion conditions such as 4 mol/L NaOH solutions, 1/6 solid to liquid, 2 h dissolving time, and a temperature of 423 K. The residual zircon (84% Zr) was subjected to complete digestion using NaOH with a zircon-to-alkali ratio of 1/1.5 and a fusion temperature of 923 K. ZrO2-NPs were synthesized using the hydrothermal technique at 473 K for 7 h. The calcined ZrO2-NPs were characterized by X-ray diffraction, scan electron microscope, and transmittance electron microscope. Purified silica was also obtained as a by-product from washing solutions of fused zircon.

Preparation of biomass-based hydrogels and their efficient heavy metal removal from aqueous solution

In this work, a porous tobacco straw-based polyacrylic acid hydrogel STS-PAA with high adsorption performance was prepared by polymerizing pretreated waste tobacco straw (TS) with acrylic acid/potassium acrylate by UV radiation initiation. The adsorption performance of metal ions was investigated. The effects of different temperatures (25°C, 35°C, and 45°C), adsorption times (1-420 min), pH values (2.0-6.0) and initial concentrations (0.25-4.0 mmol L^-1) of metal ions on the adsorption amount of heavy metal ions were investigated. The results showed that the hydrogel had a high removal rate of Pb²⁺, Cd²⁺ and Hg²⁺ in aqueous solution. The adsorption of Pb²⁺ was particularly effective. When C₀ = 4.0 mmol L^-1, pH = 6, the equilibrium adsorption amount of Pb²⁺, Cd²⁺ and Hg²⁺ reached 1.49 mmol g^-1, 1.02 mmol L^-1 and 0.94 mmol g^-1, respectively. The chemical structure and morphology of the hydrogels were characterized by FT-IR, EDS, SEM and XPS. The Langmuir model fits well with the adsorption system. The kinetic data suggest the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ follow the pseudo-first-order model. This indicates that STS-PAA adsorption of three heavy metal ions is monolayer physical adsorption. Thermodynamic analysis shows that the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ by STS-PAA is an endothermic (ΔH>0) entropy increase (ΔS>0) non-spontaneous reaction.