Enhanced removal of Cr(III)-EDTA chelates from high-salinity water by ternary complex formation on DETA functionalized magnetic carbon-based adsorbents

The Design of a Novel Alkali-Activated Binder for Solidifying Silty Soft Clay and the Study of Its Solidification Mechanism

In order to overcome the problems of the high economic and environmental costs of a traditional ordinary portland cement-based binder, this study used self-combusted coal gangue (SCCG), granulated blast furnace slag (GBFS) and phosphorous slag (PS) to prepare a novel SCCG-GBFS-PS (SGP) ternary alkali-activated binder for solidifying silty soft clay (SC). Firstly, the parameters of the SGP ternary binder were optimized using orthogonal experiments. Then the effects of the SGP ternary binder content (mass ratio of the SGP ternary binder and the SGP-solidified soil), initial water content of SC (mass ratio of SC' water and SC) and types of additives on the unconfined compressive strength (UCS) of the SGP-solidified soil were analyzed. Finally, the hydration products and microstructure of the SGP-solidified soil were analyzed to investigate the solidification mechanism of the SGP ternary binder. The results showed that the optimal mass ratio of GBFS and PS is 2:1, and the optimal alkali activator content (mass ratio of Na2O and the SGP ternary binder) and modulus of alkali activator (molar ratio of SiO2 and Na2O of alkali activator) were 13% and 1.3, respectively. When the SGP ternary binder content was 16% and the initial water content of SC was 35%, the SGP-solidified soil met the requirement of UCS for tertiary cured soil. The incorporation of triethanolamine and polyvinyl alcohol improved the UCS, while the incorporation of Na2SO4 significantly deteriorated the UCS of the SGP-solidified soil. The C-S-H gels and C(N)-A-S-H gels generated by hydration of the SGP-solidified soil were interspersed, interwoven and adhered to each other to form a network-like space structure that played the roles of skeleton, bonding soil particles and filling pores, which improved the macroscopic properties of the SGP-solidified soil. The results of this study provide a reference for the design and development of a solid waste-based binder for solidifying SC.

Corrosion process of stainless steel in natural brine as a source of chromium and iron - the need for routine analysis

The corrosion of the installations carrying high salinity water is particularly important in the case of utility and therapeutic waters, such as natural brine. The analysis of such complex systems is challenging in the context of routine analysis of Fe and Cr. Both elements can be determined by UV-Vis spectrophotometry after only 1 : 100 dilution and liquid-liquid extraction (LODFe = 0.03 mg L-1) or thermal chloride stripping (LODCr = 0.02 mg L-1). The corrosion process was characterized. Electrochemically accelerated corrosion showed uneven decomposition of the steel components - Cr is less easily released to the solution than Fe. Iron comprises 53% of the dissolved part, and Cr comprises 8.6%, while the steel originally contained 62% of Fe and 18% of Cr. During the short-term (one week) contact of the brine with stainless steel, the amounts of Fe and Cr released to the brine were insignificant from the perspective of its therapeutic value.

Exploring the potential of Fe(III)-EGTA and Fe(III)-DTPA as the catalysts to enhance UV/persulfate in the degradation of aqueous sulfamethazine

The combination of UV and water-soluble Fe(III) complexes is an effective method for generating Fe(II) in situ for activating advanced oxidation processes. This study explored the potential of Fe(III)-diethylenetriaminepentaacetic acid (Fe(III)-DTPA) and Fe(III)-ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (Fe(III)-EGTA) in activating the UV/persulfate (UV/PS) for sulfamethazine removal. The initial screening showed that Fe(III)-EGTA and Fe(III)-DTPA could significantly improve the rate of sulfamethazine removal. The optimum molar ratios of persulfate to Fe(III)-DTPA and Fe(III)-EGTA were 100:1 and 100:2.5. The predicted percentage of sulfamethazine removal under the optimized conditions, obtained using response surface methodology, was ~99% for both catalysts. The pH range of 6 to 8 did not significantly affect the performance of UV/PS in the removal of sulfamethazine. The percentage sulfamethazine removal in the selected water samples was ranged from 93.6% to 99.6%, agreeing with the predicted value. The performance of both catalysts in activating UV/PS is comparable with that of the frequently used Fe(III)-EDDS. PRACTITIONERS POINTS: The potential of Fe(III)-DTPA and Fe(III)-EGTA in activating UV/persulfate (UV/PS) was explored. Fe(III)-DTPA and Fe(III)-EGTA improved the performance of UV/PS in sulfamethazine removal. Fe(III)-DTPA and Fe(III)-EGTA are effective in catalyzing UV/PS under pH 6 to 8. The performance of Fe(III)-DTPA and Fe(III)-EGTA is comparable with well-studied Fe(III)-EDDS.

Adsorptive removal of Cr(III)-EDTA chelate from an aqueous solution by magnetic mesoporous silica microspheres

The 3-aminopropyltrimethoxysilane-modified magnetic mesoporous adsorbent (FNMs/APTES) was synthesized and applied to remove Cr(III)-EDTA chelates from water. The characterization of FNMs/APTES showed that the prepared adsorbent with a magnetic mesoporous structure was successfully grafted by APTES, which has good stability under acid conditions. The maximum capacities of FNMs/APTES for Cr(III)-EDTA adsorption at 15, 25 and 35 °C and pH 4.0 were 12.58, 13.13 and 14.00 mg·g^-1, respectively. The adsorption isotherm of FNMs/APTES for Cr(III)-EDTA conforms to the Freundlich model, and the adsorption kinetic model accords with the pseudo-second-order kinetic model. Adsorption of Cr(III)-EDTA on the adsorbent was not affected in the presence of Na⁺, K⁺ and Ca²⁺ even at 100 mmol·L^-1. Cr(III)-EDTA was anchored on FNMs/APTES through electrostatic interaction between protonated amino groups of adsorbents and Cr(III)-EDTA anions, and Cr(III)-EDTA chelates were adsorbed as a whole on the adsorbent. The Cr(III)-EDTA-saturated adsorbent can be readily regenerated in HCl solution and 83.03% of the initial Cr(III)-EDTA adsorption capacity remains after four adsorption-regeneration experiment cycles. The results highlighted that the FNMs/APTES as a potential adsorbent can be applied for the minimization of Cr(III)-EDTA chelates from water.

Highly efficient surface sequestration of Pb2+ and Cr3+ from water using a Mn3O4 anchored reduced graphene oxide: Selective removal of Pb2+ from real water

Owing to the ubiquitous existence of detrimental heavy metals in the environment, simple adsorption-oriented approaches are becoming increasingly appealing for the effective removal of Pb²⁺ and Cr³⁺ from water bodies. These techniques use nanocomposites (NC) of reduced graphene oxide (rGO) and Mn₃O₄ (rGO-Mn₃O₄), they employ a hydrothermal technique featuring NaBH₄ and NaOH solutions. Here, spectroscopic and microscopic instrumental techniques were used to evaluate the morphological and physicochemical characteristics of prepared reduced graphene oxide manganese oxide (rGO-Mn₃O₄), revealing that it possessed a well-defined porous structure with a specific surface area of 126 m² g^-1. The prepared rGO-Mn₃O₄ had significant adsorption efficiencies for Pb²⁺ and Cr³⁺, achieving maximum sequestration capacities of 130.28 and 138.51 mg g^-1 for Pb²⁺ and Cr³⁺, respectively, according to the Langmuir model. These adsorption capacities are comparable to or greater than those of previously reported graphene-based materials. The Langmuir isotherm and pseudo-second-order models adequately represented the experimental results. Thermodynamic analysis revealed that adsorption occurred through spontaneous endothermic reactions. Recycling studies showed that the developed r-GO-Mn₃O₄ had excellent recyclability, with <70% removal at the 5th cycle; its feasibility was evaluated using industrial wastewater, suggesting that Pb²⁺ was selectively removed from Pb²⁺ and Cr³⁺ contaminated water. The instrumental analysis and surface phenomena studies presented here revealed that the adsorptive removal processes of both heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation. Overall, the developed rGO-Mn₃O₄ has the potential to be a high-value adsorbent for removing heavy metals.

Waste Mineral Wool and Its Opportunities-A Review

Massive waste rock wool was generated globally and it caused substantial environmental issues such as landfill and leaching. However, reviews on the recyclability of waste rock wool are scarce. Therefore, this study presents an in-depth review of the characterization and potential usability of waste rock wool. Waste rock wool can be characterized based on its physical properties, chemical composition, and types of contaminants. The review showed that waste rock wool from the manufacturing process is more workable to be recycled for further application than the post-consumer due to its high purity. It also revealed that the pre-treatment method—comminution is vital for achieving mixture homogeneity and enhancing the properties of recycled products. The potential application of waste rock wool is reviewed with key results emphasized to demonstrate the practicality and commercial viability of each option. With a high content of chemically inert compounds such as silicon dioxide (SiO₂), calcium oxide (CaO), and aluminum oxide (Al₂O₃) that improve fire resistance properties, waste rock wool is mainly repurposed as fillers in composite material for construction and building materials. Furthermore, waste rock wool is potentially utilized as an oil, water pollutant, and gas absorbent. To sum up, waste rock wool could be feasibly recycled as a composite material enhancer and utilized as an absorbent for a greener environment.