Catalytic reduction of nitrogen monoxide using iron-nickel oxygen carriers derived from electroplating sludge: Novel method for the collaborative emission decrease of polluting gases.

The valorization of electroplating sludge (ES) for high added value presents greater economic and environmental benefits than conventional treatment methods such as thermal processing, solidification, and landfill. Inspired by the mechanism of chemical looping combustion (CLC), this study developed a novel cost-effective method for denitrification by preparing FeNi-OCs from ES to achieve the synergistic reduction of CO and NO emissions. The phase structure, micromorphology, and valence state changes of the FeNi-OC catalyst during the CO-catalyzed reduction of NO and the pathway for catalytic denitrification using FeNi-OCs were analyzed. Results showed that CO could reduce FeNi-OCs to FeNi, and the reduced FeNi was subsequently oxidized back to FeNi-OCs by NO, a process analogous to CLC. During experiments, the simultaneous consumption of CO and NO gases was observed at 350 °C. This phenomenon was highly pronounced at 600 °C, where the CO and NO concentrations decreased from initial values of 8550 and 470 ppm, respectively, to 6719 and 0 ppm, respectively, with conversion rates of 21.41 % and 100 %, respectively. Hence, synergistic emission reduction was achieved. Further experiments also indicated that the addition of 1.5 % ES during iron ore sintering could substantially reduce the CO and NO concentrations in the sintering flue gas from 1268.32 and 244.81 ppm, respectively, to 974.51 and 161.11 ppm, respectively.

Research progress in the degradation of printing and dyeing wastewater using chitosan based composite photocatalytic materials.

The surge in economic growth has spurred the expansion of the textile industry, resulting in a continuous rise in the discharge of printing and dyeing wastewater. In contrast, the photocatalytic method harnesses light energy to degrade pollutants, boasting low energy consumption and high efficiency. Nevertheless, traditional photocatalysts suffer from limited light responsiveness, inadequate adsorption capabilities, susceptibility to agglomeration, and hydrophilicity, thereby curtailing their practical utility. Consequently, integrating appropriate carriers with traditional photocatalysts becomes imperative. The combination of chitosan and semiconductor materials stands out by reducing band gap energy, augmenting reactive sites, mitigating carrier recombination, bolstering structural stability, and notably advancing the photocatalytic degradation of printing and dyeing wastewater. This study embarks on an exploration by initially elucidating the technical principles, merits, and demerits of prevailing printing and dyeing wastewater treatment methodologies, with a focal emphasis on the photocatalytic approach. It delineates the constraints encountered by traditional photocatalysts in practical scenarios. Subsequently, it comprehensively encapsulates the research advancements and elucidates the reaction mechanisms underlying chitosan based composite materials employed in treating printing and dyeing wastewater. Finally, this work casts a forward-looking perspective on the future research trajectory of chitosan based photocatalysts, particularly in the realm of industrial applications.

Low-temperature CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation for selective catalytic reduction of NO using NH3: A structure-activity relationship study.

CeCoMnOx spinel-type catalysts for the selective catalytic reduction of NO using NH3 (NH3-SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnOx spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH3-SCR activities of the CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnOx spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnOx-C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnOx-N-400), and thus CeCoMnOx-C have better low-temperature NH3-SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnOx-C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100-125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnOx-N-400 at 100-125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnOx-C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization.

A novel approach for the resource utilization of zinc-bearing dust and sludge via the blast furnace main trough.

Minimizing the environmental impact of zinc-bearing dust and sludge (ZDS) while efficiently extracting valuable metals from its intricate mix has become a pressing issue for steel mills. To facilitate comprehensive ZDS usage, we propose a novel approach for recycling ZDS in the blast furnace main trough. This work explores the self-reduction reaction principles of carbon-containing pellets derived from ZDS. Moreover, it examines the consequent alterations in the physical and chemical properties of molten iron and slag. The molten iron temperature inversely correlates with the number of added pellets; the temperature declines as more pellets are introduced. To restrict the molten iron's temperature decrease to within 30℃, it is advisable to limit the quantity of pellets added to 20 kg per ton of molten iron. At 1500℃, the self-reduction reaction of the pellet initiates 1.5 min post its introduction into the molten iron and concludes 12 min thereafter. The pellet mass percentage entering the molten iron is 32 %, whereas the mass percentage of iron elements within the pellet entering molten iron is 64 %. The pellet addition results in an uptick in blast furnace slag viscosity, yet it remains within an acceptable viscosity range (<1Pa·s).

Can microplastics and disinfectant resistance genes pose conceivable threats to water disinfection process?

Microplastic pollution in the environment has aroused widespread concerns, however, the potential environmental risks caused by excessive use of disinfectants are still unknown. Disinfectants with doses below the threshold can enhance the communication of resistance genes in pathogenic microorganisms, promoting the development and spread of antimicrobial activity. Problematically, the intensification of microplastic pollution and the increase of disinfectant consumption will become a key driving force for the growth of disinfectant resistance bacteria (DRB) and disinfectant resistance genes (DRGs) in the environment. Disinfection plays a crucial role in ensuring water safety, however, the presence of microplastics and DRGs seriously disturb the water disinfection process. Microplastics can reduce the concentration of disinfectant in the local environment around microorganisms and improve their tolerance. Microorganisms can improve their resistance to disinfectants or generate resistance genes via phenotypic adaptation, gene mutations, and horizontal gene transfer. However, very limited information is available on the impact of DRB and DRGs on disinfection process. In this paper, the contribution of microplastics to the migration and transmission of DRGs was analyzed. The challenges posed by the presence of microplastics and DRGs on conventional disinfection were thoroughly discussed. The knowledge gaps faced by relevant current research and further research priorities have been proposed in order to provide a scientific basis in the future.

Synthesis of triethylenetetramine modified sodium alginate/CuS nanocrystal composite for enhanced Cr(VI) removal: Performance and mechanism.

Photocatalysis has been widely used for the removal of hexavalent chromium from wastewater as an efficient and environmental friendly method. However, conventional photocatalysts generally exhibit poor adsorption properties toward Cr(VI), resulting in unsatisfactory performance in high concentrated wastewaters. In this study, we synthesized a novel composite material with high Cr(VI) adsorption ability by blending prepared CuS nanocrystals into triethylenetetramine modified sodium alginate for the enhanced photocatalytic removal of Cr(VI). Effect of CuS dosage, pH value, light source and intensity were discussed for the optimum Cr(VI) removal conditions. The synthesized composite has shown good adsorption performance toward Cr(VI) and the overall removal rate reached 98.99 % within 50 min under UV light irradiation with citric acid as hole scavenger. Adsorption isotherm, thermodynamics, and kinetics with corresponding model fitting were discussed, which suggested that the monolayer and chemical adsorption dominated the adsorption process. Characterization results indicated that amino and hydroxyl groups contributed electrons in the photocatalysis reaction for the reduction of Cr(VI) to Cr(III). CuS nanocrystals can enhance the surface charge and light absorbance ability of the composite, and the Cr(VI) removal was governed by electrostatic interaction and photo-induced redox reaction.

Subcritical hydrothermal oxidation of semi-dry ash from iron ore sintering flue gas desulfurization: Experimental and kinetic studies.

Realization of low temperature and high efficiency oxidation of CaSO3 is the key to solve the issue of ecological hazards caused by semi-dry sintering flue gas desulfurization ash. The subcritical hydrothermal technology was employed for the oxidation of CaSO3, achieving 89.83% of CaSO3 at 180 °C, 2 MPa for 120 min with a solid-to-liquid ratio of 1:20. The macroscopic oxidation kinetics of CaSO3 in the subcritical hydrothermal reaction system was investigated. A mathematical model was established, incorporating the intrinsic reaction, CaSO3 dissolution, oxygen diffusion and CaSO4 precipitation. It was concluded that the macroscopic oxidation of CaSO3 was co-controlled by the oxygen diffusion and CaSO4 precipitation. Subcritical hydrothermal technology promises not only higher efficiency, but more importantly, potentially "one-step" preparation of CaSO4 whiskers, enabling cost-effective and high value-added resource utilization of the semi-dry FGD ash.

Recent advances in the research on effects of micro/nanoplastics on carbon conversion and carbon cycle: A review.

Massive production and spread application of plastics have led to the accumulation of numerous plastics in the global environment so that the proportion of carbon storage in these polymers also increases. Carbon cycle is of fundamental significance to global climate change and human survival and development. With the continuous increase of microplastics, undoubtedly, there carbons will continue to be introduced into the global carbon cycle. In this paper, the impact of microplastics on microorganisms involved in carbon transformation is reviewed. Micro/nanoplastics affect carbon conversion and carbon cycle by interfering with biological fixation of CO2, microbial structure and community, functional enzymes activity, the expression of related genes, and the change of local environment. Micro/nanoplastic abundance, concentration and size could significantly lead to difference in carbon conversion. In addition, plastic pollution can further affect the blue carbon ecosystem reduce its ability to store CO2 and marine carbon fixation capacity. Nevertheless, problematically, limited information is seriously insufficient in understanding the relevant mechanisms. Accordingly, it is required to further explore the effect of micro/nanoplastics and derived organic carbon on carbon cycle under multiple impacts. Under the influence of global change, migration and transformation of these carbon substances may cause new ecological and environmental problems. Additionally, the relationship between plastic pollution and blue carbon ecosystem and global climate change should be timely established. This work provides a better perspective for the follow-up study of the impact of micro/nanoplastics on carbon cycle.

Carbonyl sulfur removal from blast furnace gas: Recent progress, application status and future development.

Carbonyl sulfide (COS), a poisonous and harmful gas, is found in industrial gas products from various coal-firing processes. The emission of COS into the atmosphere contributes to aerosol particles that affect the global climate, posing a risk to climate change and population health. In recent years, the total amount of anthropogenic COS emissions has increased significantly, resulting in the prominent COS pollution problem and becoming a vital environmental issue. This review summarizes the research progress of removing COS from industrial gases. According to the characteristics of different industrial gas products, the COS removal mechanism and influence factors, as well as the advantages and disadvantages for various methods, are discussed, including oxidation, absorption/adsorption, hydrogenation, and hydrolysis. Although COS emission control technologies have attracted widespread attention, the progress of application in blast furnace gas purification has been extremely slow, insufficient and sporadic. To fill the gap, this work provides a timely review on blast furnace gas characteristics and application process of various methods for removing COS from blast furnace gas with varying compositions, and their challenges and future development. This work aims to provide guidance on how effective processes and techniques for removal of COS from blast furnace gas can be developed. This review emphasizes the desirability of direct COS removal from blast furnace gas compared to expensive terminal desulfurization technologies. Furthermore, the development of a new process for low-temperature COS removal from blast furnace gas based on a dual-functional catalyst of hydrolysis/adsorption is advocated.

Interfacial Area Transport Equation for Bubble Coalescence and Breakup: Developments and Comparisons.

Bubble coalescence and breakup play important roles in physical-chemical processes and bubbles are treated in two groups in the interfacial area transport equation (IATE). This paper presents a review of IATE for bubble coalescence and breakup to model five bubble interaction mechanisms: bubble coalescence due to random collision, bubble coalescence due to wake entrainment, bubble breakup due to turbulent impact, bubble breakup due to shearing-off, and bubble breakup due to surface instability. In bubble coalescence, bubble size, velocity and collision frequency are dominant. In bubble breakup, the influence of viscous shear, shearing-off, and surface instability are neglected, and their corresponding theory and modelling are rare in the literature. Furthermore, combining turbulent kinetic energy and inertial force together is the best choice for the bubble breakup criterion. The reviewed one-group constitutive models include the one developed by Wu et al., Ishii and Kim, Hibiki and Ishii, Yao and Morel, and Nguyen et al. To extend the IATE prediction capability beyond bubbly flow, two-group IATE is needed and its performance is strongly dependent on the channel size and geometry. Therefore, constitutive models for two-group IATE in a three-type channel (i.e., narrow confined channel, round pipe and relatively larger pipe) are summarized. Although great progress in extending the IATE beyond churn-turbulent flow to churn-annual flow was made, there are still some issues in their modelling and experiments due to the highly distorted interface measurement. Regarded as the challenges to be addressed in the further study, some limitations of IATE general applicability and the directions for future development are highlighted.

Mechanistic study of Cr (VI) removal by modified alginate/GO composite via synergistic adsorption and photocatalytic reduction.

A novel composite material was prepared by blending graphene oxide into polyethyleneimine grafted sodium alginate. The synthesized material was investigated as adsorbent and photocatalyst for the removal of hexavalent chromium (Cr (VI)) from aqueous solutions. The composite material has shown remarkable removal efficiency for Cr (VI) in high initial concentration solutions as the removal rate reached 86.16% and 99.92% for adsorption and photoreduction, respectively. We discovered experimentally that the adsorption was dominated via electrostatic interaction while the blending of GO could contribute in stimulating electrons for the photoreduction process. Moreover, the photoreduction can alter the surface charge of chromium species, thus electrostatic repulsion could regenerating the active sites of composite spontaneously. The conduction band energy was calculated as -2.04 eV, which proved that blending GO can narrow the bandgap of the composite material, thus enhance the light response and the photoreduction ability towards Cr (VI).

Influence of cerium doping on Cu-Ni/activated carbon low-temperature CO-SCR denitration catalysts.

In this study, to evaluate the effects of two methods for activation of nitric acid, air thermal oxidation and Ce doping were applied to a Cu-Ni/activated carbon (AC) low-temperature CO-SCR denitration catalyst. The Cu-Ni-Ce/AC0,1 catalyst was prepared using the ultrasonic equal volume impregnation method. The physical and chemical structures of Cu-Ni-Ce/AC0,1 were studied using scanning electron microscopy, Brunauer-Emmett-Teller analysis, Fourier-transform infrared spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, CO-temperature programmed desorption (TPD) and NO-TPD characterisation techniques. It was found that the denitration efficiency of 6Cu-4Ni-5Ce/AC1 can reach 99.8% at a denitration temperature of 150 °C, a GHSV of 30 000 h-1 and 5% O2. Although the specific surface area of the AC activated by nitric acid was slightly lower than that activated by air thermal oxidation, the pore structure of the AC activated by nitric acid was more developed, and the number of acidic oxygen-containing functional groups was significantly increased. Ce metal ions were inserted into the graphite microcrystalline structure of AC, splitting it into smaller graphene fragments, whereby the dispersibility of Cu and Ni was improved. In addition, many reaction units were formed on the catalyst surface, which could adsorb more CO and NO reaction gases. With the increase in Ce doping, the relative proportions of Cu2+/Cu n+, Ni3+/Ni n+ and surface adsorbed oxygen (Oα) in the Cu-Ni-Ce/AC0,1 catalyst increased. In addition, after the introduction of Ce into Cu-Ni/AC, the amount of weak and medium acids significantly increased. This may be due to the Ce species or its influence on the Cu/Ni species. Further, the active sites of the acid were more exposed. According to the results of the study, a composite metal oxide CO-SCR denitration mechanism is proposed. Through the oxidation-reduction reaction between the metals, the reaction gas of CO and NO is adsorbed and the incoming O2 is converted into (Oα), which promotes the conversion of NO into NO2. The CO-SCR reaction is accelerated, and the rate of low-temperature denitration was increased. Overall, the results of this study will provide theoretical support for the research and development of low-temperature denitration catalysts for sintering flue gas in iron and steel enterprises.

Adsorption of heavy metal ions by sodium alginate based adsorbent-a review and new perspectives.

With the development of modern industry, heavy metal pollution is one of the most important environmental issues. Due to its simplicity and low-cost, adsorption is considered as a green and environmental friendly method to remove heavy metals from industrial effluents. Sodium alginate is a natural polysaccharide, which consists of abundant hydroxyl and carboxyl groups, has been widely reported as the raw material for the adsorption of heavy metals from aqueous solutions. By surface grafting and cross-linking, adsorbents synthesized from sodium alginate have exhibited large uptake capacities as well as high removal rates for heavy metal ions. However, the poor physical strength and plain thermostability have significantly limited the utilization of sodium alginate based materials in industrial applications. Moreover, reductions of specific metal ions were observed in some studies, of which the reduction mechanism is not clearly clarified. In this work, the development of sodium alginate based adsorbents was summarized, including the physicochemical properties of the polymer, the modification of sodium alginate, sodium alginate based composite materials, and the adsorption behaviors as well as the mechanism. Chelation, electrostatic interaction, ion exchange, reduction and photocatalytic reduction were involved in the adsorption process, which can be determined by chemical characterization with further elucidation by density functional theory calculation. Finally, the limitations of sodium alginate based adsorbents were revealed with suggestions for future research.

Selective adsorption of Pd (II) by ion-imprinted porous alginate beads: Experimental and density functional theory study.

In this study, a novel thiourea grafted porous sodium alginate-based adsorbent was synthesized by combining ion-imprinting and direct templating method. Due to ion-imprinting, the prepared adsorbent has demonstrated outstanding selectivity towards Pd (II) from bi-metallic solution at different pH values. Langmuir and both pseudo-first and pseudo-second kinetic equations were used to describe the adsorption isotherm and kinetics, respectively. FT-IR, XPS, and SEM-EDX analyses suggested that selective adsorption of Pd (II) was dominated by electrostatic interactions at pH 1.0 and chelation on imprinted sorption sites at pH 3.0. Density functional theory (DFT) calculation further explained the effect of ion-imprinting and provided two binding configurations, which is consistent with characterization analyses. The pregnant adsorbent can be regenerated and reused by thiourea solution in dilute hydrochloric acid. Therefore, the synthesized adsorbent would be useful as a selective adsorbent for the enrichment of Pd (II) from effluents.

High-yield synthesis of Ce modified Fe-Mn composite oxides benefitting from catalytic destruction of chlorobenzene.

Ce-Fe-Mn catalysts were prepared by an oxalic acid assisted co-precipitation method. The influence of Ce doping and calcination temperature on the catalytic oxidation of chlorobenzene (as a model VOC molecule) was investigated in a fixed bed reactor. The Mn3O4 phase was formed in Ce-Fe-Mn catalysts at low calcination temperatures (<400 °C), which introduced more chemisorbed oxygen, and enhanced the mobility of O atoms, resulting in an improvement of the reduction active of Mn3O4 and Fe2O3. Additionally, CeO2 has strong redox properties, and Ce4+ would oxidize Mn x+ and Fe x+. Therefore, the interaction of Ce, Fe and Mn can improve the content of surface chemisorbed oxygen. As compared with Fe-Mn catalysts, the catalytic conversion of chlorobenzene over Ce(5%)-Fe-Mn-400 was about 99% at 250 °C, owing to high specific surface area, Mn3O4 phase, and Ce doping. However, with the increase in roasting temperature, the performance of the catalysts for the catalytic combustion of chlorobenzene was decreased, which probably accounts for the formation of the Mn2O3 phase in Ce-Fe-Mn-500 catalysts, leading to a decrease in the specific surface area and concentration of chemically adsorbed oxygen. As a result, it can be expected that the Ce-Fe-Mn catalysts are effective and promising catalysts for chlorobenzene destruction.

Effect of Calcination Temperature on the Activation Performance and Reaction Mechanism of Ce-Mn-Ru/TiO2 Catalysts for Selective Catalytic Reduction of NO with NH3.

In this study, anatase TiO2-supported cerium, manganese, and ruthenium mixed oxides (CeO x -MnO x -RuO x /TiO2; CMRT catalysts) were synthesized at different calcination temperatures via conventional impregnation methods and used for selective catalytic reduction (SCR) of NO x with NH3. The effect of calcination temperature on the structure, redox properties, activation performance, surface-acidity properties, and catalytic properties of the CMRT catalysts was investigated. The results show that the CMRT catalyst calcined at 350 °C exhibits the most efficient low-temperature (<120 °C) denitration activity. Moreover, the selective catalytic oxidation (SCO) reaction of ammonia is intensified when the reaction temperature is >200 °C, which leads to a decrease in the N2 selectivity of the CMRT catalysts and further results in an increase in the production of NO and N2O byproducts. X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy show that the CMRT catalyst calcined at 350 °C contains more Ce4+, Mn4+, Ru4+, and lattice oxygen, which greatly improve the catalyst's ability to activate NO that promotes the NH3-SCR reaction. The Ru n+ sites of the CMRT catalyst calcined at 250 °C are the competitive adsorption sites of NO and NH3 molecules, while those of the CMRT catalyst calcined at 350 and 450 °C are active sites. Both the Langmuir-Hinshelwood (L-H) mechanism and the Eley-Rideal (E-R) mechanism occur on the surface of the CMRT catalyst at the low reaction temperature (100 °C).

Investigation of reducing particulate matter (PM) and heavy metals pollutions by adding a novel additive from metallurgical dust (MD) during coal combustion.

In this study, a novel additive from metallurgical dust(MD)was applied to reduce particulate matter (PM) emissions and heavy metals pollutions during coal combustion. PM samples were collected and divided into 13 stages from 0.03 µm to 10 µm. Results showed that the irregular morphology of fine particles with equal to/less than 2.5 µm (PM2.5), fine particles with equal to/less than 4 µm (PM4) and fine particles with equal to/less than10 µm (PM10) gradually became dense with increasing of MD content. The PM10 concentration with 10% MD dosage was about 3 times higher than that of raw coal. Zn, Ti, Cu and Cr were the most abundant elements in all particulate matters (PMs), meanwhile, heavy metals accumulated into large particles with increasing MD content. The mechanism of reducing PM emissions indicated that MD reacted with nucleation elements (Pb, Cd, etc.) and trapped a large amount of alkali metal (Na/K), which aggregated into large particles. The study highlights the potential of adding MD into coal to prevent the attachment of heavy metals onto ultrafine particles, thereby reducing the heavy metals emissions.

Study of Catalytic Combustion of Dioxins on Ce-V-Ti Catalysts Modified by Graphene Oxide in Simulating Iron Ore Sintering Flue Gas.

Ce-V-Ti and Ce-V-Ti/GO catalysts synthesized by the sol-gel method were used for the catalytic combustion of dioxins at a low temperature under simulating sintering flue gas in this paper. The catalytic mechanism of Ce-V-Ti catalysts modified with graphene oxides (GO) at a low temperature was revealed through X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2-TPR) and Fourier transform infrared (FTIR). During the tests, chlorobenzene (CB) was used as a model reagent since the dioxins are poisonous. The results showed that introducing GO to Ce-V-Ti catalysts can improve the specific surface area and promote the CB adsorption on the surface of catalysts. Simultaneously, the Ce-V-Ti with 0.7 wt % GO support showed the high activity with the conversion of 60% at 100 °C and 80% at 150 °C. The adsorb ability of catalysts is strengthened by the electron interaction between GO and CB through π-π bond. In the case of Ce-V-Ti catalysts, Ce played a major catalytic role and V acted as a co-catalytic composition. After GO modification, the concentration of Ce3+ and V4+ were enlarged. The synergy between Ce3+ and V3+ played the critical role on the low-temperature performance of catalysts under sintering flue gas.