Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Abstract

As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at a certain region, and was used for the adsorption of lead ions from aqueous solutions, thereby broadening the research field for the practical application of CSHW. Its adsorption capacity was significantly influenced by various parameters, particularly, the pH level and initial lead concentration. The pH value highly affected the hydrolysis degree of lead ions and dominated the adsorption of lead. The equilibrium isotherms under two different temperatures were simulated using Langmuir, Freundlich, and Temkin models. Both Langmuir and Temkin models showed a good fit to the data. Combined with the well-fitted pseudo-second-order model, the adsorption mechanism was thought to be a chemisorption process that was enforced by the ion exchange reaction. In addition, the specific crystal structure of CSHW revealed that ion exchange reaction occurred on the (010) and (100) facets due to their preferential growth and negatively charged property. The residual solid phase after adsorption was collected and detected using X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. Results revealed that PbSO 4 was formed on the surface of CSHW. The alkaline condition introduced the tribasic lead sulfate, and thus reduced the stability of the adsorption system.

The Influence of the Textural Characteristics of the Hierarchical Porous Carbons on the Removal of Lead and Cadmium Ions from Aqueous Solution

“…The optimum conditions for the factors of Pb 2+ uptake were found to be at high values of A (90-100 mg/L) and B (5 mg/L). Based on the chemical speciation of cadmium and lead, it is averred that the major species of the two metals that will dominate at the pH range investigated are the ionic Cd 2+ and Pb 2+ [66][67][68]. Formation of the hydroxide species of the metals can occur at pH 6-7.…”

Bioadsorption of lead(II) over the pulp of Acrocomia aculeata

“…The pH was found to have a pH of 5.84 at 25.4 °C. As lead has a solubility between a pH of 2 to 7, distilled water was used in the following solutions (Wang et al, 2017). Lead nitrate, Pb(NO3)2, were used in the preparation of all solutions.…”

Nano-enhanced Dialytic Fluid Purification: CFD Modeling of Pb(II) Removal by Manganese Oxide

“… 8 , 9 In low ionic strength and slightly acidic aqueous conditions, lead is predominantly in its free divalent form. 9 , 10 Hexagonal birnessite (δ-MnO 2 ) was used as the model nanoadsorbent given its layered surface area, negative surface charge at circumneutral pH, and high adsorption capacity 11 − 13 that makes it a natural high affinity, 14 strong sorber 15 for divalent lead.…”