Modeling, Simulation, Optimization, and Experimental Verification of Mercury Removal onto Natural and Sulfur-Impregnated Zeolite Clinoptilolite—Assessment of Feasibility for Remediation of Mercury-Contaminated Soil

Abstract

In this paper, a series of equilibrium and kinetic experiments of Hg(II) removal in a single-stage batch reactor on natural (NZ) and sulfur-impregnated zeolite (SZ) were performed. Batch sorption of Hg(II) on zeolites was studied using different isothermal and kinetic models. It was found to be best described by the Brouers-Sotolongo isotherm and the Vermeulen’s approximation, which were applied in optimizing the mass and contact time in two-stage cross-current and counter-current flow batch reactors based on the desired criterion of 99.9% removal efficiency. Mathematical models for minimizing zeolite mass and contact time were developed and experimentally verified. The optimum minimum masses of NZ and SZ were calculated for all systems, and a significant saving in SZ consumption was found when the counter-current design was applied. The toxicity characteristic leaching procedure (TCLP) was applied to mercury contaminated soil from the Idrija mine region in Slovenia to evaluate potential soil toxicity. The results showed that the soil is extremely contaminated and represents hazardous waste. The addition of zeolites significantly reduced the concentration of leached Hg, with the most satisfactory results obtained with SZ. It was found that at the lowest dose of 0.25 g of SZ, the leached Hg concentration was reduced below the maximum concentration criterion of 0.2 mg/L according to the TCLP test. This study revealed that SZ could be a potential sorbent for in situ remediation of mercury contaminated soil.

Soil Organic Matter Composition and pH as Factors Affecting Retention of Carbaryl, Carbofuran and Metolachlor in Soil

“…Hence, it can be concluded that the lower values of the constant obtained for loamy soil indicate a higher degree of surface coverage with the pesticides compared to sandy loam soil material. Furthermore, from the b T value, the nature of the process may be elucidated [ 53 ]. In the case of physical sorption, it should be lower than 4.184 kJ mol −1 (1 kcal mol −1 ), while for chemical sorption it is above 41,840 kJ mol −1 (10 kcal mol −1 ).…”

“…The value of the mean sorption energy provides information about chemical and physical sorption. The E a value ranges from approximately 1 kJ mol −1 to 8 kJ mol −1 for physical sorption and from 8 kJ mol −1 to 16 kJ mol −1 for chemical sorption [ 53 ].…”

Influence of SOM Composition, Clay Minerals, and pH on 2,4-D and MCPA Retention in Peri-Urban Soils

“…The Temkin b T constant (amount of energy that is released), revealed a decreasing trend when comparing soil L to C. It can be concluded that the lower values of the constant obtained for loamy soil indicate the higher degree of surface coverage with the pesticides, compared to sandy loam soil material [69]. In addition, the values of the b T parameter (Table 5) suggest that the sorption of 2,4-D and MCPA on L and C soil is presumably of a physical nature, due to the energy magnitude lower than 4.184 kJ mol −1 (1 kcal mol −1 ) [70].…”

Fabrication of Novel Nanosulfur-Modified Activated Carbon Adsorbent for Elemental Mercury Removal from Flue Gas

“…Adsorbent injection technology is considered the most promising and mature strategy for mercury control, wherein Hg 0 is converted to Hg p and subsequently captured by downstream particulate control devices. Various types of adsorbents have been designed, and halogen (chlorine and bromine)-modified adsorbents have shown superior mercury removal performance and been commercially utilized. − However, mercury and halogen species may leach out in the spent halogen-modified adsorbents, posing risks to the environment. , To address this issue, sulfur doping on the adsorbent surface has been explored as it can enhance the adsorbent’s performance and produce chemically stable mercury sulfide (HgS). − The active material in the sulfur-impregnated adsorbent is demonstrated to be elemental sulfur. − However, the utilization rate of the active material in existing sulfur-impregnated adsorbents is low due to the large sulfur-to-carbon ratio . Specifically speaking, the loaded sulfur is not only on the adsorbent surface but also in the adsorbent bulk phase, while mercury in the flue gas could only react with the adsorbent surface in the duct.…”