Magnetic hydrochar derived from waste lignin for thallium removal from wastewater: Performance and mechanisms

Taloring sawdust derived hydrochar via red mud for cadmium removal: Electron transfer insight and recyclability assessment

Iron modified bio-adsorbents gained a lot of attention recently, especially some iron-contain wastes were employed for fabrication. However, the influence of indigenous impurities in wastes was merely investigated. In this study, red mud (RM), an iron-rich by-product was employed as source to prepare Fe modified hydrochar (RM@HC) by a facile hydrothermal method, and then employed for Cd(II) removal from wastewater. The RM@HC demonstrated excellent adsorption performance with capacity of 598.26 mg/g and maintained with a wide pH range. Further, the removal mechanisms were comprehensively elucidated and calculated, which was attributed to the various interactions include physical adsorption (29.07%), reduction (27.61%), and co-precipitation (25.81%). Moreover, the abundant metal oxides in RM@HC contributed to the removal through co-precipitation by building a highly alkaline environment. This work provided a promising choice for the sustainable reutilization of RM by designing a green bio-adsorbent to remove heavy metals from wastewater.

Amphichdiral enhancement on singlet oxygen generation and stable thallium immobilization using iron-driven copper oxide

Thallium (Tl) as a prominent priority contaminant in aquatic environment necessitates rigorous regulation. However, limited horizon devotes the impact of selective oxidation on the process of thallium purification. In this study, selective active radical of singlet oxygen (1O2) was continually generated for Tl(Ⅰ) oxidation accomplished with efficient Tl(Ⅲ) immobilization using iron-driven copper oxide (CuFe)/peroxymonosulfate (PMS). Fe-doping changed the active center of electronic structure for enhancing the catalytic and adsorptive reactivities, and installed magnetism for solid-liquid separation. Rapid reaction rate (0.253 min-1) coupled with vigorous elimination efficiency (98.32%) relied on electrostatic attraction, surface complexation, and H-bond interaction. EPR and XPS analyses demonstrated that the synergistic effects of ≡ Cu(Ⅰ)/≡Cu(Ⅱ) and ≡ Fe(Ⅲ)/≡Fe(Ⅱ) redounded to the sustained generation of 1O2 through the pathway of PMS → •O2- → 1O2, and 1O2 exploited an advantage to selectively oxidize Tl(Ⅰ) to Tl(Ⅲ). 3D isosurface cubic charts revealed that the immobilizing ability of Tl(Ⅲ) hydrate for CuFe was notably superior to that of Tl(Ⅲ) hydrate for CuO and Tl(Ⅰ) hydrate for CuO/CuFe, which further attested surface reactivity promoted stable immobilization form. This work develops the continuous generation of 1O2 and stable immobilization with the goal of efficiently cleansing Tl-containing wastewater.

Efficient incorporation of highly migratory thallium into struvite structure: Unraveling the stabilization mechanisms from a mineralogical perspective

The remediation of high-concentration thallium (Tl+) contaminated wastewater is a critical environmental concern. Current research emphasizes the effectiveness of adsorption and oxidation methods for Tl+ treatment, yet challenges persist in enhancing their performance. This study explores the feasibility of emergency Tl+ wastewater treatment and elucidates the mechanisms of Tl+ incorporation into mineral structures, with a focus on the struvite mineral as a framework for Tl+ integration via NH4+ ion exchange. To assess the efficacy and mechanisms of Tl+ immobilization, we utilized comprehensive analytical techniques, including X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TG), and Density Functional Theory (DFT) calculations. The findings reveal that struvite adsorbs Tl+ onto its surface, followed by an ion exchange process between monovalent cations (NH4+/K+) within the structure and Tl+. Ultimately, Tl+ is incorporated in the form of a (NH4,Tl)MgPO4 solid solution within the structure, achieving a remarkable maximum incorporation capacity of 320.56 mg/g, which significantly surpasses the capacity of typical adsorbents. The findings demonstrate significant Tl+ incorporation, validating the approach for emergency wastewater treatment and suggesting the potential of mineralogy in environmental remediation. This research contributes to advancing heavy metal wastewater treatment strategies, offering a foundation for further investigation.

Chromium immobilization from wastewater via iron-modified hydrochar: Different iron fabricants and practicality assessment

The recycling of industrial solid by-products such as red mud (RM) has become an urgent priority, due to their large quantities and lack of reutilization methods can lead to resource wastage. In this work, RM was employed to fabricate green hydrochar (HC) to prepare zero-valent iron (ZVI) modified carbonous materials, and conventional iron salts (IS, FeCl3) was applied as comparison, fabricated HC labeled as RM/HC and IS/HC, respectively. The physicochemical properties of these HC were comprehensively characterized. Further, hexavalent chromium (Cr(VI)) removal performance was assessed (375.66 and 337.19 mg/g for RM/HC and IS/HC, respectively). The influence of dosage and initial pH were evaluated, while isotherms, kinetics, and thermodynamics analysis were also conducted, to mimic the surface interactions. The stability and recyclability of adsorbents also verified, while the practical feasibility was assessed by bok choy-planting experiment. This work revealed that RM can be used as a high value and green fabricant for HC the effective removal of chromium contaminants from the wastewater.

Recent advances and future perspective on lignocellulose-based materials as adsorbents in diverse water treatment applications

The growing shortage of non-renewable resources and the burden of toxic pollutants in water have gradually become stumbling blocks in the path of sustainable human development. To this end, there has been great interest in finding renewable and environmentally friendly materials to promote environmental sustainability and combat harmful pollutants in wastewater. Of the many options, lignocellulose, as an abundant, biocompatible and renewable material, is the most attractive candidate for water remediation due to the unique physical and chemical properties of its constituents. Herein, we review the latest research advances in lignocellulose-based adsorbents, focusing on lignocellulosic composition, material modification, application of adsorbents. The modification and preparation methods of lignin, cellulose and hemicellulose and their applications in the treatment of diverse contaminated water are systematically and comprehensively presented. Also, the detailed description of the adsorption model, the adsorption mechanism and the adsorbent regeneration technique provides an excellent reference for understanding the underlying adsorption mechanism and the adsorbent recycling. Finally, the challenges and limitations of lignocellulosic adsorbents are evaluated from a practical application perspective, and future developments in the related field are discussed. In summary, this review offers rational insights to develop lignocellulose-based environmentally-friendly reactive materials for the removal of hazardous aquatic contaminants.

Efficient and effective immobilization of tetracycline and copper from wastewater by zero-valent iron fabricated hydrochar derived from walnut peel

Antibiotics and heavy metals often coexist as non-point-source contaminants in wastewater and their quite contrary physiochemical properties make their co-removal processes challenging. In this work, a bifunctional zero-valent iron-modified hydrochar derived from walnut peel (MWPHC) was synthesized, which was then applied for the simultaneous removal of tetracycline (TC) and Cu(II) from wastewater. Based on the characterizations, Fe0 species were successfully distributed on the surface of the walnut peel substrates. The TC and Cu(II) could be synergistically immobilized, and bridging effects were observed between them, and MWPHC exhibited excellent ability on the simultaneous removal of TC (qmax = 433.59 mg/g) and Cu(II) (qmax = 586.25 mg/g). Furthermore, the engineering feasibility of the MWPHC was evaluated using column and regeneration experiments. These results shed light on the tailored MWPHC as an environmental functional material for pollution control of co-existing antibiotic and heavy metal contaminants in agro-industrial wastewater.