resource-recycling-red-soil-to-synthesize-fe2o3fau-type-zeolite

Resource Recycling of Red Soil to Synthesize Fe<sub>2</sub>O<sub>3</sub>/FAU-type Zeolite Composite Material for Heavy Metal Removal

Heavy metal-polluted water is of great concern to human health and the eco-environment. In situ water remediation techniques enabled by highly efficient ...

Southern University of Science and Technology

As one of the biggest hazardous solid waste in the metallurgical industry, arsenic-bearing gypsum (ABG) is a great threat to environmental safety owing to possible leakage and diffusion contamination. However, the reclamation of ABG suffers great challenges due to its worthless constituents and high arsenic leaching. In this study, an ABG was reclaimed as more valuable bassanite (CaSO∙0.5HO) and anhydrite (CaSO). Firstly, the overmuch arsenic in ABG was removed to below 150 mg/kg (Japan standard value) using acid extraction. Then, the sludge was mixed with a small amount of CaO and heated at 150 °C and 900 °C to produce bassanite and anhydrite, respectively. In this calcination, gypsum dehydration and arsenic stabilization were combined. In Japan standard leaching test (JSLT), the arsenic leaching concentrations from bassanite (5.1 μg/L) and anhydrite (1.3 μg/L) satisfied the environmental criteria (<10 μg/L) set by Japan government and remained stable for three months. In toxicity characteristic leaching procedure (TCLP), arsenic leaching concentrations remained at 1.61 and 0.61 mg/L, much lower than the limitation (<5 mg/L). Moreover, the arsenic leaching behavior implied that higher temperature was benefited to arsenic stability, which indicated that the arsenic stabilization process was temperature dependent. By XRD analyses, it was found that heating (over 100 °C) could effectively promote arsenic immobilization through reducing the carbonation influence. And the temperature dependence was attributed to the formation of insoluble svabite (Ca(AsO)OH) at high temperature (300-900 °C).

Reclamation of an arsenic-bearing gypsum via acid washing and CaO-As stabilization involving svabite formation in thermal treatment.

The hazardous red mud (RM) with high As/F mobility and heavy metal contaminated soil have constituted severe environmental threats. This work demonstrates a "waste to eco-material" strategy through a reliable and low-cost protonation approach to eliminate the As/F leaching risk of RM, and then recycle it as heavy metal passivators for Pb/As polluted soil remediation. The As/F anions have been immobilized by the protonated Fe/Al (hydr)oxides within RM via the formation of stable As/F compounds during the protonation process, which satisfies the requirement by the World Health Organization (As leaching <0.01 mg/L; F leaching <0.8 mg/L). Moreover, in the oilseed rape pot experiments, by adding 30 g/kg stabilized RM into Pb/As polluted soils (100 ~ 300 ppm), benefited from its large adsorption capacity, approximately 40.9 ~ 49.7% Pb and 40.8 ~ 54.8% As concentrations in the plant are reduced without adverse effects. The whole process for RM treatment and soil remediation is cost-effective, straightforward and eco-friendly without secondary pollution or soil degradation. This research provides a green chemical strategy to address both RM recycling and heavy metal contaminated soil remediation problems, which shows high economic feasibility and ecological benefits.

Protonation stabilized high As/F mobility red mud for Pb/As polluted soil remediation.

Search for simple and efficient recycling methods to utilize spent lithium-ion batteries is crucial for achieving sustainable resource development and reducing the hazardous materials released from the spent batteries. Herein, we have developed a new strategy to utilize the spent LiFePO batteries by utilizing the cathode plate as raw material to synthesize mesoporous core-shell adsorbent Mm@SiO (Mm denoted as the magnetic material) through a simple alkaline leaching process. The as-converted material exhibits excellent adsorption capacity when it has been used to remove heavy metal ions in heavy metal polluted water. The adsorption capacities for Cu, Cd, and Mn have been achieved up to 71.23, 80.31 and 68.73 mg g, respectively. The detailed adsorption mechanism has been elucidated with comprehensive characterization techniques, including TEM, XPS, NEXAS, and EXAFS, the edge shared [CuO] bipyramids can be fit against the EXAFS data to represent the atomic-scale local structure after Mm@SiO adsorbs Cu. The present work demonstrates a novel routine to reutilize the spent lithium batteries, which is of great importance to achieve sustainable development based on the "waste-to-treasure" and "waste-to-control-waste" strategy for simultaneously reducing the hazardous release from industrial solid waste and heavy metal polluted water.

High-efficiency core-shell magnetic heavy-metal absorbents derived from spent-LiFePO Battery.

Due to the large output and potential ecological risks, disposal of engineering abandoned soils (EAS) has become an enormous challenge for human society. Herein, EAS has been transformed into microporous analcime (ANA) zeolite material through a fast, energy-efficient, and straightforward conversion process. The as-synthesized ANA has been employed to remediate Cu-polluted soil, which shows a significant ecological restoration function in a vegetable pot experiment. With 25 g/kg ANA into Cu contaminated soil (total Cu concentration: 200 ppm), the Cu accumulation concentration in vegetables has been decreased from 5.60 down to 1.80 mg/kg (approaching the background Cu level 1.70 mg/kg in vegetables). Detailed mechanism study combining with DFT calculations reveals that the Cu in soil has been captured both inside the ANA pore channels and on the surface via ion-exchange and surface adsorption mechanism. The whole process, including ANA synthesis and Cu polluted soil remediation, has been optimized to show a valuable conceptual model to recycle EAS resource and in-situ remediate Cu polluted soil.

Remediation of Cu-polluted soil with analcime synthesized from engineering abandoned soils through green chemistry approaches.

Both soil erosion and soil contamination pose critical environmental threats to the Chinese Loess Plateau (CLP). Green, efficient and feasible remediation technologies are highly demanded to meet these challenges. Herein we propose a unique "soil for soil-remediation" strategy to remediate the heavy metal polluted soil in CLP by converting loess into zeolite for the first time. With a simple template-free route, the natural loess can be converted into cancrinite (CAN) type of zeolite. A highly crystalline CAN was obtained via hydrothermal treatment at 240 C for 48 h, with a precursor alkalinity of Na/(Si+Al)> 2.0. The as-synthesized CAN zeolite exhibits excellent remediation performance for Pb(II) and Cu(II) polluted soil. Plant assay experiment demonstrates that CAN can significantly restrain the uptake and accumulation of Pb(II) and Cu(II) ions in vegetables, with a high removal efficiency up to 90.7% and 81.4%, respectively. This work demonstrates a "soil for soil-remediation" strategy to utilize the natural loess for soil remediation in CLP, which paves the way for developing green and sustainable remediation eco-materials with local loess as raw materials.

Converting loess into zeolite for heavy metal polluted soil remediation based on "soil for soil-remediation" strategy.

Battery deionization (BDI) offers a powerful platform for integrating water treatment and energy conversion. Exploring novel BDI electrode materials with high energy storage capacity and high efficiency for both cations and anions removal is the key to advancing the BDI technique. Herein, we report the first BDI electrode material capable of simultaneously removing Cl (58.4 mg g) and Na (8.7 mg g) in water with a reversible capacity of 160 mAh g. In situ powder X-ray diffraction (PXRD) unravels that the dual-ion removal capability is attributed to a novel reversible electrochemical driven phase segregation reaction mechanism between NaBiOCl and the in situ formed metallic Bi. The unique dual-ion storage capability demonstrated with the NaBiOCl electrode indicates that exploring electrochemical reversible phase segregation electrode material holds great promise for advancing the BDI electrode for future desalination techniques and aqueous rechargeable battery systems.

Electrochemical Driven Phase Segregation Enabled Dual-Ion Removal Battery Deionization Electrode.

Wastewater with complex compositions of both heavy metals and organic pollutants is of critical environmental and socioeconomic threat worldwide, which urgently requires feasible remediation technologies to target this challenge. In this study, natural chalcopyrite (CuFeS, NCP), the most abundant copper-based mineral in the Earth's crust, has been discovered to be a heterogeneous catalyst that can activate peroxydisulfate (PDS) for the simultaneous degradation of organic pollutant Rhodamine B (RhB) and reduction of hexavalent chromium (Cr(VI)). Batch experimental results indicate that both RhB and Cr(VI) could be simultaneously removed under a near-neutral condition in NCP/PDS combined system. The radicals SO and OH generated from PDS activation are the main oxidative species detected by electron paramagnetic resonance (EPR) spectroscopy. SO acted as a predominant role in RhB degradation, while Cr(VI) reduction is mainly attributed to the oxidization of S and S species on NCP surface, as well as the photoreduction performance of NCP, which could be enhanced by the intermediates generated from RhB degradation. Density functional theory (DFT) calculation results disclose that Fe is the critical catalytic site for PDS activation. This work demonstrates a user-friendly strategy for remediation of complex wastewater containing both heavy metal and organic pollutants by combining photoreduction and advanced oxidation processes (AOPs) with natural minerals. It paves a way for wastewater treatment by utilizing low-cost natural abundant minerals as catalysts.

Enhanced Cr(VI) reduction on natural chalcopyrite mineral modulated by degradation intermediates of RhB.

Herein, a novel "waste reclamation for soil remediation" strategy has been developed for both alkaline waste red mud (RM) recycling and heavy metal (HM) polluted soil remediation. Through a direct one-pot hydrothermal reaction process, the Al, Si, alkali, and FeO components in waste RM have been transferred into ferric oxide decorated ANA-type zeolite (FeO-ANA). As tested by the HMs polluted soil remediation and oilseed rape planting experiment, when 25 g/kg FeO-ANA is added into the Pb, Cu, Cr and anionic AsO polluted soil (HM concentration: 100-200 mg/kg), it can effectively suppress the HMs mobility in soil and reduce the bio-accumulation concentrations of HMs in the harvested oilseed rape (reduce ratio: 37.9-69.5%). The detailed mechanism study using energy dispersive X-ray energy spectroscopy, in-depth X-ray photoelectron spectroscopy and density function theory calculation concludes that the Cu, Pb and Cr in soil have been adsorbed and trapped in the framework structure of ANA in FeO-ANA mainly via the cation exchange process. While the anionic AsO species are mainly caught by the FeO component in FeO-ANA via surface adsorption. Overall, this work firstly transforms waste RM into FeO-ANA for soil remediation, which is valuable to waste resource recycling and environmental conservation.

Transferring waste red mud into ferric oxide decorated ANA-type zeolite for multiple heavy metals polluted soil remediation.

Langmuir adsorption model is a classic physical-chemical adsorption model and is widely used to describe the monolayer adsorption behavior at the material interface in environmental chemistry. Traditional adsorption dynamic modeling solely considered the surface physiochemical interaction between the adsorbent and adsorbate. The surface reaction dynamics resulting from the heterogeneous surface and intrinsic electronic structure of absorbents were rarely considered within the reported adsorption experiments. Herein, by employing the chlorine hybrid graphene oxide () to adsorb Ag in an aqueous solution, complicated molecular dynamics significantly deviated from the monolayer adsorption mechanism, as suggested by Langmuir adsorption curve fitting, has been elucidated down to atomic scale. In the time-dependent Ag adsorption experiments, both Ag single atoms and Ag/AgCl nanoparticle heterostructures are observed to be formed sequentially on . These observations indicate that for the surface adsorption dynamics, not only the surface chemical adsorption process involved but also photoreduction and the C-Cl bond cleavage reaction has been heavily engaged within the  interface, suggesting a much more complicated vision rather than the monolayered adsorption algorithm as derived from curve fitting. This study uses  as a simple example to disclose the complicated adsorption dynamic process underneath Langmuir adsorption curve fitting. It advocates the necessity of imaging the interfacial atomic-scale dynamic structure with high-resolution microscopy techniques in modern adsorption studies, rather than simply explaining the adsorption dynamics relying on the curve fitting results due to the complicated physiochemical reactivity of the adsorbents.

Dazhong Yang

Southern University of Science and Technology

Resource Recycling of Red Soil to Synthesize Fe₂O₃/FAU-type Zeolite Composite Material for Heavy Metal Removal

Dazhong Yang

Southern University of Science and Technology

Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal

Resource Recycling of Red Soil to Synthesize Fe₂O₃/FAU-type Zeolite Composite Material for Heavy Metal Removal