Lan Xiang

Hydrothermal hydrolysis of TiOSO₄ is a critical step in recovering titanium from sulfuric-acid leachates derived from titanium-bearing blast furnace slag (TBFS). This research examined the effects of Mg, Al, and Fe impurities on TiOSO₄ hydrolysis and assessed modified coal gasification slag (m-CGS) as a substrate for TiO₂ deposition. Mg, Al, and Fe sulfates suppressed Ti hydrolysis but yielded smaller, more highly dispersed metatitanic acid particles; at comparable hydrolysis ratios, the mean particle size decreased from 305 to 143 nm. Thermodynamic calculations indicated that the additional sulfate reduced the [TiO²⁺][OH⁻]² concentration product and the theoretical hydrolysis ratio. In contrast, m-CGS accelerated hydrolysis, particularly at lower temperatures. The lower Avrami exponents observed upon the addition of m-CGS indicated an increased contribution of heterogeneous particle growth. Particle size distribution analysis and TEM-EDS confirmed Ti deposition on the m-CGS surfaces. These results support direct TiO₂ deposition from impurity-bearing TiOSO₄ solutions as a route to the integrated utilization of TBFS and CGS.

Semiconductor-based sensors continue to face challenges related to poor response and stability in humid conditions. Herein, Au nanoparticles (NPs) are successfully deposited on sulfur-vacancies-enriched MoS₂ (SV-MoS₂/Au) to develop an enhanced humidity-resistant trace NO₂ sensor. The SV-MoS₂/Au sensor exhibits a high response (115%) and rapid response/recovery rate (10 s/7 s) toward 50 ppb of NO₂ under visible light illumination. Additionally, it exhibits satisfactory reversibility, long-term stability, low detection limit (0.1 ppb), and good selectivity in a humid environment (relative humidity ≈60%) at room temperature. The sulfur-vacancies-enriched structure facilitates firm anchoring of abundant Au NPs on the surface of SV-MoS₂, leading to an effective utilization of water molecules to generate increasing free radicals (·O₂^- and ·OH) in the humid air. The in situ FTIR results and theoretical calculations demonstrate that the increasing formation of free radicals could effectively inhibit the formation of HNO₃ and HNO₂ during the reaction between NO₂ and H₂O. Consequently, the sensors exhibit remarkable responsiveness to NO₂, providing important new perspectives for the future design of room-temperature semiconductor-based humidity-resistant gas sensors.

Coal gasification slag (CGS) is a major byproduct of coal gasification, yet its complex mineral composition hinders efficient resource utilization. In this study, selective leaching of CGS by hydrochloric acid was investigated to clarify phase-dependent dissolution behavior from thermodynamic and structural perspectives. Leaching experiments conducted at 80 °C with 1.4 mol·L⁻¹ HCl revealed rapid dissolution within the first 10 min, with Ca, Al, and Mg exhibiting higher leaching ratios than Fe and Si. X-ray diffraction analysis showed that anorthite and gehlenite dissolved almost completely at the initial stage and augite decomposed progressively, whereas quartz, iron oxide, and aluminum oxide remained relatively stable. Thermodynamic calculations of Gibbs free energy changes predicted the reactivity sequence: anorthite < gehlenite < augite < aluminum oxide < iron oxide, consistent with experimental observations. Structural analysis of Ca–O coordination environments further explained the preferential dissolution trends of silicates, as lower coordination numbers and longer Ca–O bond distances facilitate protonation and hydration. Hydrochloric acid treatment increased the specific surface area from 98 to 329 m²·g⁻¹ and produced hollow silica-rich composite oxides. These findings provide mechanistic insight into selective phase dissolution and establish a foundation for the high-value utilization of CGS.

A novel method for selectively removing F from F/P‐containing CaSO₄·2H₂O slurry using CaCl₂ as the precipitant is reported. Experimental results indicate that under conditions of 25°C, a Ca/F ratio of 2.5, and acidic pH (0.9–4.0), the F removal and P retention performance is optimal, where the removal rate of soluble F increases from 67.93% to 95.15%, while the loss rate of soluble P rises from 0% to 46.67%. At pH ≥ 6.0, the P loss rate exceeds 60%. Thermodynamic equilibrium calculations were conducted to reveal the equilibrium concentration distributions of F and P components and precipitation behavior of F and P at varying pH. At pH ≥ 4.4, binary co‐precipitation of CaF₂ and CaHPO₄ occurs, hindering F removal while retaining P. At pH = 5.6–11.8, ternary co‐precipitation of CaF₂, Ca₃(PO₄)₂, and CaHPO₄ further complicates selective F removal. In contrast, at pH = 0.9–4.0, the method effectively removes F while preserving P, aligning closely with the experimental results.

Globally, phosphogypsum (PG) is the primary by-product of the phosphorus industry. Aspergillus niger (A. niger), one of the most powerful types of phosphate-solubilizing fungi (PSF), can secrete organic acids to dissolve the phosphates in PG. This study investigated heavy metal (HM) remediation by PG and A. niger under the co-existence of Pb and Cd. It demonstrated that 1 mmol/L Pb²⁺ stimulated the bioactivity of A. niger during incubation, based on the CO₂ emission rate. PG successfully functioned as P source for the fungus, and promoted the growth of the fungal cells. Meanwhile, it also provided sulfates to immobilize Pb in the solution. The subsequently generated anglesite was confirmed using SEM imaging. The immobilization rate of Pb reached over 95%. Under co-existence, Pb²⁺ and 0.01 mmol/L Cd²⁺ maximized the stimulating effect of A. niger. However, the biotoxicity of Pb²⁺ and elevated Cd²⁺ (0.1 mmol/L) counterbalanced the stimulating effect. Finally, 1 mmol/L Cd²⁺ dramatically reduced the fungal activity. In addition, organic matters from the debris of A. niger could still bind Pb²⁺ and Cd²⁺ according to the significantly lowered water-soluble Pb and Cd concentrations. In all treatments with the addition of Cd²⁺, the relatively high biotoxicity of Cd²⁺ induced A. niger to absorb more Pb²⁺ to minimize the sorption of Cd²⁺ based on the XRD results. The functional group analysis of ATR-IR also confirmed the phenomenon. This pathway maintained the stability of Pb²⁺ immobilization using the fungus and PG. This study, hence, shed light on the application of A. niger and solid waste PG to remediate the pollution of Pb and Cd.

Real-time and sensitive detection of methane (CH₄) is vital to the safety of life and production due to the explosivity and greenhouse effect of methane. Currently, metal oxide semiconductor (MOS)-based chemiresistive sensors are considered as an effective approach for its low cost, highly tunable structures and easy fabrication. However, disadvantages like high working temperature, low sensitivity, unsatisfying selectivity etc. limit its potential wide application. In order to achieve the goal of high-performance MOS-based methane sensors, in this review, from the basic mechanism of MOS-based gas sensing and the property of methane, possible strategies of improving methane sensing performances in multiple aspects have been summarized systematically, including sensitivity, selectivity, stability and humidity resistance. Recent progress in the research and development of metal oxide semiconductor-based methane sensor technology is also surveyed in this review. Finally, the future trends and perspectives of MOS-based chemiresistive methane sensors are proposed.