Effective removal of Pb (II) from wastewater by zinc-iron bimetallic oxide-modified walnut shell biochar: A combined experimental and DFT calculation approach

Efficient capture and detoxification of gaseous arsenic trioxide from flue gas using silicomanganese alloy dust

This study aims to develop efficient capture materials for gaseous arsenic trioxide (As2O3(g)) that can prevent arsenic poisoning in selective catalytic reduction (SCR) systems and reduce atmospheric arsenic emissions from coal-fired power plants. One kind of metallurgical dust from a silicomanganese alloy plant (named as SiMnD) was found to be cost-effective and environmentally friendly for As2O3(g) removal from flue gas for the first time. The sorbent showed excellent performance for gaseous arsenic trioxides capture with a good capacity of 13.82 mg/g at 450 °C in 60 min, which was better than the other reported metal oxides at high temperature. The As2O3(g) capture capacity in 12-h continuous test reached as high as 118.16 mg/g without penetration, and the sorbent showed good long-term durability and pretty good resistance to high concentrations of nitric oxide (NO), sulfur dioxide (SO2) and carbon dioxide (CO2). The sorbent also exhibited good recyclability even after five regeneration cycles. Nearly 92% of As2O3(g) was transformed into manganese (II) pyroarsenate (Mn2As2O7), manganese arsenate (MnAsO4) and diarsenic pentoxide (As2O5) after capture with lower toxicity. The results of Toxicity Characteristic Leaching Procedure (TCLP) and five-step sequential extraction demonstrated that spent SiMnD exhibited low arsenic bioavailability, indicating reduced environmental mobility of arsenic species. Trimanganese tetroxide (Mn3O4) and blythite (Mn3Mn2(SiO4)3) were the most essential active component for As2O3(g) removal and detoxification. The optimal As2O3(g) capture temperature of SiMnD was 450 °C which was suitable to be applied before SCR with little operating cost. SiMnD was proved to be one excellent capture and detoxification agent for As2O3(g) in flue gas at a lower temperature with promising application prospects.

Bimetallic Fe-Mo modified N-doped carbon materials activating peroxymonosulfate for acetaminophen degradation: Synergistic effects of free radicals and electron transfer process

This study aimed to synthesize a bimetallic Fe-Mo modified N-doped carbon material (FeMo@NCN) using a simple pyrolysis method. Structural and physical characterizations confirmed the successful incorporation of Fe and Mo into the catalyst. The FeMo@NCN/PMS system exhibited an excellent acetaminophen (ACE) degradation rate (kobs = 0.1232 min-1), which is 51 times higher than that of NCN/PMS system (kobs = 0.0024 min-1). Mechanistic analysis revealed that the Fe/Mo interaction, as well as the synergistic effects between Mo-N and Fe-N sites, facilitated the continuous generation of reactive oxygen species (ROS), including SO4•- and •OH. Specifically, Mo doping to promoted the regeneration of Fe2+, contributing to the recovery of catalytic activity and playing a key role in maintaining high degradation efficiency. Furthermore, electrochemical analysis demonstrated that the Fe and Mo doping significantly enhanced the electronic transfer properties of the material, revealing the existence of an electron transfer-based non-radical pathway. Additionally, FeMo@NCN exhibited remarkable stability across a wide pH range (3-9). The intermediate degradation products and degradation pathways of ACE were identified, and the toxicity of ACE and its degradation products were evaluated. This work provides new insights into improving the performance of carbon-based materials for efficient removal of refractory organic compounds in PMS systems.

Bimetallic Zinc-Iron-Modified Sugarcane Bagasse Biochar for Simultaneous Adsorption of Arsenic and Oxytetracycline from Wastewater

Arsenic (As), a highly toxic and carcinogenic heavy metal, poses significant risks to soil and water quality, while oxytetracycline (OTC), a widely used antibiotic, contributes to environmental pollution due to excessive human usage. Addressing the coexistence of multiple pollutants in the environment, this study investigates the simultaneous adsorption of As(III) and OTC using a novel bimetallic zinc-iron-modified biochar (1Zn-1Fe-1SBC). The developed adsorbent demonstrates enhanced recovery, improved adsorption efficiency, and cost-effective operation. Characterization results revealed a high carbon-to-hydrogen ratio (C/H) and a specific surface area of 1137 m2 g-1 for 1Zn-1Fe-1SBC. Isotherm modeling indicated maximum adsorption capacities of 34.7 mg g-1 for As(III) and 172.4 mg g-1 for OTC. Thermodynamic analysis confirmed that the adsorption processes for both pollutants were spontaneous (ΔG < 0), endothermic (ΔH > 0), and driven by chemical adsorption (ΔH > 80 kJ mol-1), with increased system disorder (ΔS > 0). The adsorption mechanisms involved multiple interactions, including pore filling, hydrogen bonding, electrostatic attraction, complexation, and π-π interactions. These findings underscore the potential of 1Zn-1Fe-1SBC as a promising adsorbent for the remediation of wastewater containing coexisting pollutants.