Inhalation of respirable silica particles can cause serious lung diseases (e.g., silicosis and lung cancer), and the toxicity of respirable silica is highly dependent on its crystal form. Common combustion processes such as coal and biomass burning can provide high temperature environments that may alter the crystal forms of silica and thus affect its toxic effects. Although crystalline silica (i.e., quartz, tridymite, and cristobalite) were widely found at different temperatures during the burning processes, the sources and crystal transformation pathways of silica in the burning processes are still not well understood. Here, we investigate the crystal transformation of silica in the coal and biomass combustion processes and clarify the detailed transformation pathways of silica for the first time. Specifically, in coal burning process, amorphous silica can transform into quartz and cristobalite starting at 1100 °C, and quartz transforms into cristobalite starting at 1200 °C; in biomass burning process, amorphous silica can transform into cristobalite starting at 800 °C, and cristobalite transforms into tridymite starting at 1000 °C. These transformation temperatures are significantly lower than those predicted by the classic theory due to possibly the catalysis of coexisting metal elements (e.g., aluminum, iron, and potassium). Our results not only enable a deeper understanding on the combustion-induced crystal transformation of silica, but also contribute to the mitigation of population exposure to respirable silica.

In recent years, biochar has become of considerable interest for environmental applications, it can be used as a catalyst for sulfides reduction of perchloroethylene, but the crucial role of biochar properties played in catalyzing dechlorination remained ambiguous investigation. To pinpoint the critical functional groups, the modified biochars were respectively produced by HNO₃, KOH and H₂O₂ with similar dimensional structures but different functional groups. Combined with the adsorption and catalytic results of different biochars, the acid-modified biochar had the best catalytic performance (99.9% removal) due to the outstanding specific surface area and ample functional groups. According to characterization and DFT results, carboxyl and pyridine nitrogen exhibited a positive correlation with the catalytic rate, indicating that their contribution to catalytic performance. Customizing biochar with specific functional groups removed depth demonstrated that the carboxyl was essential component. Further, alkaline condition was conducive to catalytic reduction, while tetrachloroethylene cannot be reduced under acidic conditions, because HS⁻ and S²⁻ mainly existed in alkaline environment and the sulfur-containing nucleophilic structure formed with biochar was more stable under this condition. Overall, this study opens new perspectives for in situ remediation by biochar in chlorinated olefin polluted anoxic environment and promotes our insight of modifying for biochar catalyst design.

The treatment of contaminants from lignocellulosic biorefinery effluent has recently been identified as a unique challenge. This study focuses on removing phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) from lignocellulosic biorefinery wastewater (BRW) applying a laccase-assisted approach. Cassava waste was used as a substrate to produce the maximum yield of laccase enzyme (3.9 U/g) from Pleurotus ostreatus. Among the different inducers supplemented, CuSO₄ (0.5 mM) showed an eight-fold increase in enzyme production (30.8 U/g) after 240 h of incubation. The catalytic efficiency of laccase was observed as 128.7 ± 8.47 S⁻¹mM⁻¹ for syringaldazine oxidation at optimum pH 4.0 and 40 °C. Laccase activity was completely inhibited by lead (II) ion, mercury (II) ion, sodium dodecyl sulphate, sodium azide and 1,4 dithiothretiol and induced significantly by manganese (II) ion and rhamnolipid. After treating BRW with laccase, the concentrations of PAHs and phenolic contaminants of 1144 μg/L and 46160 μg/L were reduced to 96 μg/L and 16100 μg/L, respectively. The ability of laccase to effectively degrade PAHs in the presence of different phenolic compounds implies that phenolic contaminants may play a role in PAHs degradation. After 240 h, organic contaminants were removed from BRW in the following order: phenol >2,4-dinitrophenol > 2-methyl-4,6-dinitrophenol > 2,3,4,6-tetrachlorophenol > acenaphthene > fluorine > phenanthrene > fluoranthene > pyrene > anthracene > chrysene > naphthalene > benzo(a)anthracene > benzo(a)pyrene > benzo(b)fluoranthene > pentachlorophenol > indeno(1,2,3-cd)pyrene > benzo(j) fluoranthene > benzo[k]fluoranthène. The multiple contaminant remediation from the BRW by enzymatic method, clearly suggests that the laccase can be used as a bioremediation tool for the treatment of wastewater from various industries.

Catalytic pyrolysis is a promising chemical recycling technology to supplement mechanical recycling since plastics can be broken down into monomers or converted to the required fuels and chemicals. In this study, a microwave (MW) -responsive SiC foam@zeoltie core-shell structured catalyst was proposed for the catalytic pyrolysis of polyolefins. Under microwave irradiation, the SiC foam core works as both microwave adsorber and catalyst support, thus concentrating the generated heat energy on the ZSM-5 zeolite shell, where the catalytic reaction takes place. SiC foam with an open cellular structure can also improve the global transport of mass and heat during plastics pyrolysis. In this work, the effects of the SiO₂/Al₂O₃ ratio and alkaline treatment of ZSM-5 zeolite coated SiC foam under MW irradiation on the variations in product distribution from low-density polyethylene (LDPE) pyrolysis were investigated at 450 °C. The results indicated that the appropriate acidity and pore structure were crucial to upgrading gas and liquid products. Particularly, the creation of a mesoporous structure in ZSM-5 zeolite via alkaline treatment could improve the diffusion of large molecules and products, thus significantly increasing the selectivity of high-valued light olefins and aromatics while inhibiting the formation of unwanted alkanes, which are expected in the chemical industry. Concretely, the concentration of olefins in gas increased to 51.0 vol% for ZSM-5(50)-0.25AT, and 65.6 vol% for ZSM-5 (50)-0.50AT, compared with 45.2 vol% for the parent ZSM-5(50). The relative concentration of aromatics in liquid decreased from 96.6% for ZSM-5(50) to 75.9% for ZSM-5(50)-0.25AT, and 71.1% for ZSM-5(50)-0.50AT. Given the respective yield of gas and liquid, the total selectivity of C2–C4 olefins and aromatics for mesoporous ZSM-5 zeolites could reach 58.6–64.9% during LDPE pyrolysis, which were higher than that for the parent ZSM-5 zeolite.

Fe–N co-doped biochar is recently an emerging carbocatalyst for persulfate activation in situ chemical oxidation (ISCO). However, the involved catalytic mechanisms remain controversial and distinct effects of coexisting water components are still not very clear. Herein, we reported a novel N-doped biochar-coupled crystallized Fe phases composite (Fe@N-BC₈₀₀) as efficient and low-cost peroxydisulfate (PDS) activators to degrade bisphenol A (BPA), and the underlying influencing mechanism of coexisting inorganic anions (IA) and humic constituent. Due to the formation of graphitized nanosheets with high defects (AI index>0.5, ID/IG = 1.02), Fe@N-BC₈₀₀ exhibited 2.039, 5.536, 8.646, and 23.154-fold higher PDS catalytic activity than that of Fe@N-BC₆₀₀, Fe@N-BC₄₀₀, N-BC, BC. Unlike radical pathway driven by carbonyl group and pyrrolic N of low/mid-temperature Fe@N–BCs. The defective graphitized nanosheets and Fe-Nx acted separately as electron transfer and radical pathway active sites of Fe@N-BC₈₀₀, where π-π sorption assisted with pyrrolic N and pore-filling facilitated BPA degradation. The strong inhibitory effects of PO₄³⁻ and NO₂⁻ were ascribed to competitive adsorption of phosphate (61.11 mg g⁻¹) and nitrate (23.99 mg g⁻¹) on Fe@N-BC₈₀₀ via electrostatic attraction and hydrogen bonding. In contrast, HA competed for the pyrrolic-N site and hindered electron delivery. Moreover, BPA oxidation pathways initiated by secondary free radicals were proposed. The study facilitates a thorough understanding of the intrinsic properties of designed biochar and contributes new insights into the fate of degradation byproducts formed from ISCO treatment of micropollutants.

The beta-blocker atenolol (ATE), and the selective serotonin and norepinephrine reuptake inhibitor, venlafaxine (VEN) are frequently detected in municipal wastewater effluents, but little is known about their ecotoxicological effect on aquatic animals. Herein, ATE and VEN were selected to explore their accumulation and global DNA methylation (GDM) in zebrafish tissues after a 30-day exposure. Molecular dynamics (MD) stimulation was used to investigate the toxic mechanism of ATE and VEN exposure. The results demonstrated that ATE and VEN could reduce the condition factor of zebrafish. The bioaccumulation capacity for ATE and VEN was in the order of liver > gut > gill > brain and liver > gut > brain > gill, respectively. After a 30-day recovery, ATE and VEN could still be detected in zebrafish tissues when exposure concentrations were ≥10 μg/L. Moreover, ATE and VEN induced global DNA hypomethylation in different tissues with a dose-dependent manner and their main target tissues were liver and brain. When the exposure concentrations of ATE and VEN were increased to 100 μg/L, the global DNA hypomethylation of liver and brain were reduced to 27% and 18%, respectively. In the same tissue exposed to the same concentration, DNA hypomethylation induced by VEN was more serious than that of ATE. After a 30-day recovery, the global DNA hypomethylations caused by the two drugs were still persistent, and the recovery of VEN was slower than that of ATE. The MD simulation results showed that both ATE and VEN could reduce the catalytic activity of DNA Methyltransferase 1 (DNMT1), while the effect of VEN on the 3D conformational changes of the DNMT1 domain was more significant, resulting in a lower DNA methylation rate. The current study shed new light on the toxic mechanism and potential adverse impacts of ATE and VEN on zebrafish, providing essential information to the further ecotoxicological risk assessment of these drugs in the aquatic environment.

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar (denoted as N-CSBC, O-CSBC, and B-CSBC, respectively) were fabricated in a one-step pyrolysis process to promote peroxymonosulfate (PMS) activation for the elimination of sulfathiazole (STZ) from aquaculture water. B-CSBC exhibited remarkably high catalytic activity with 92% of STZ degradation in 30 min attributed to the presence of meso-/micro-pores and B-containing functional groups (including B–N, B–C, and B₂O₃ species). Radical quenching tests revealed SO₄•⁻, HO•, and ¹O₂ being the major electron acceptors contributing to STZ removal by PMS over B-CSBC catalyst. The B-CSBC catalyst has demonstrated high sustainability in multiple consecutive treatment cycles. High salinity and the presence of inorganic ions such as chloride, enhanced the performance of the sulfate radical-carbon-driven advanced oxidation processes (SR–CAOPs) as pretreatment strategy that significantly facilitated the removal of STZ from aquaculture water. Furthermore, a potential sulfonamide-degrading microorganism, Cylindrospermum_stagnale, belonging to the phylum Cyanobacteria, was the dominant functional bacteria according to the results of high-throughput 16S rRNA gene sequencing conducted after the B-CSBC/PMS treatment. This study provides new insights into the SR–CAOP combined with bioprocesses for removing STZ from aqueous environments.

Though many studies pertaining to soil bioremediation have been performed to study the microbial kinetics in shake flasks, the process efficiency in column tests is seldom. In the present study, soil columns tests were carried out to study the biodegradation of soil contaminated with a high concentration of diesel (≈19.5 g/kg) petroleum hydrocarbons expressed as C₁₀–C₅₀. Experiments were done with crude enzymatic cocktail produced by the hydrocarbonoclastic bacterium, Alcanivorax borkumensis. A. borkumensis was grown on a media with 3% (v/v) motor oil as the sole carbon and energy source. The effects of the enzyme concentration, treatment time and oxidant on the bioremediation efficiency of C₁₀–C₅₀ were investigated. A batch test was also carried out in parallel to investigate the stability of the enzymes and the effect of the biosurfactants on the desorption and the bioconversion of C₁₀–C₅₀. Batch tests indicated that the biosurfactants significantly affected the desorption and alkane hydroxylase and lipase enzymes, maintained their catalytic activity during the 20-day test, with a half-life of 7.44 days and 8.84 days, respectively. The crude enzyme cocktail, with 40 U/mL of lipase and 10 U/mL of alkane hydroxylase, showed the highest conversion of 57.36% after 12 weeks of treatment with a degradation rate of 0.0218 day⁻¹. The results show that the soil column tests can be used to optimize operating conditions for hydrocarbon degradation and to assess the performance of the overall bioremediation process.

Because the pollutants produced by human activities have destroyed the ecological balance of natural water environment, and caused severe impact on human life safety and environmental security. Hence the task of water environment restoration is imminent. Metal-organic frameworks (MOFs), structured from organic ligands and inorganic metal ions, are notable for their outstanding crystallinity, diverse structures, large surface areas, adsorption performance, and excellent component tunability. The water stability of MOFs is a key requisite for their possible actual applications in separation, catalysis, adsorption, and other water environment remediation areas because it is necessary to safeguard the integrity of the material structure during utilization. In this article, we comprehensively review state-of-the-art research progress on the promising potential of MOFs as excellent nanomaterials to remove contaminants from the water environment. Firstly, the fundamental characteristics and preparation methods of several typical water-stable MOFs include UiO, MIL, and ZIF are introduced. Then, the removal property and mechanism of heavy metal ions, radionuclide contaminants, drugs, and organic dyes by different MOFs were compared. Finally, the application prospect of MOFs in pollutant remediation prospected. In this review, the synthesis methods and application in water pollutant removal are explored, which provide ways toward the effective use of water-stable MOFs in materials design and environmental remediation.

The search for optimal catalysts to improve the working efficiency of ozonation has always been an important issue in the research field of advanced oxidation processes. In this study, a novel catalyst, ferrosilicon, was selected as the catalyst in heterogeneous catalytic ozonation to degrade ibuprofen (IBP) in water and treat real pharmaceutical wastewater. During the procedure, 45#ferrosilicon exhibited the best catalytic activity. Under the optimized experimental conditions, the IBP removal reached 75%, which was a great improvement compared to the 37% removal by ozone alone. The 45#-ferrosilicon-catalysed ozonation also achieved 68% TOC removal for real pharmaceutical wastewater, which was 31% higher than that by ozone alone. The degradation pathway of IBP was proposed using GC/MS. The EPR test proved that the main active species in the system were free active radicals •OH, and the measured accumulative •OH amount was 102 μmol. The characterization results show that the nascent metallic oxides, hydroxides, and hydroxyoxides on the ferrosilicon surface facilitated the decomposition of ozone molecules and generation of free active radicals. The removal of target organic contaminants in the water was mainly attributed to the oxidization of these highly active species.