In view of the problems caused by chromium-containing wastewater, such as environmental pollution, biological toxicity, and human health risks. Based on fly ash adsorption and nano-FeS reduction characteristics, fly ash loaded nano-FeS composite (nFeS-FA) was synthesized using mineral supported modification technology and ultrasonic precipitation method. The effect of adsorbent dosage, initial pH, contact time, and initial concentration of the solution on the adsorption of Cr(VI) and total Cr by nFeS-FA was investigated. The characteristics of Cr(VI) and total Cr adsorption by nFeS-FA were studied using adsorption isotherms, adsorption kinetics principles, as well as XRD, TEM, SEM-EDS, and BET analysis. The results demonstrated that under the conditions of nFeS-FA of 8 g/L, initial pH of 4, contact time of 150 min, and initial concentration of the solution at 100 mg/L, nFeS-FA achieved removal efficiency of 87.85 % for Cr(VI) and 71.77 % for total Cr. The adsorption of Cr(VI) and total Cr by nFeS-FA followed the Langmuir model and pseudo-second-order kinetic model, indicating monolayer adsorption with chemical adsorption as the dominant mechanism. XRD, TEM, SEM-EDS, and BET revealed that the flaky nano-FeS was uniformly distributed on the surface of fly ash, exhibiting good dispersion and thereby increasing the specific surface area. During the adsorption experiments, nFeS-FA reacted with Cr(VI), and the generated Fe3+ mainly existed as FeOOH precipitation, while S2- reacted with Cr(III) to produce Cr2S3 precipitation. Therefore, nFeS-FA exhibited excellent adsorption performance towards Cr(VI) and total Cr. It can serve as a technological reference for the remediation of heavy metal chromium pollution in the field of water treatment.

In order to promote the development and utilization of desert sand, this study is based on researching the most suitable ratio of bio-cement, analyzing the shear strength and permeability of improved desert sand by combining bio-cement and fly ash, and clarifying the applicability of tap water in bio-cement. The relationship between the two and the microstructural properties was investigated using the results of the straight shear test and the permeability test. The results showed that the urease solution prepared with tap water had a more pronounced temperature resistance. The urea concentration and the corresponding pH environment had a direct effect on the urease activity. The calcium carbonate yield was positively correlated with the calcium concentration, and the urea concentration was higher in the ranges of 1.0-1.5 mol/L. As the enzyme-to-gel ratio decreased, the calcium carbonate precipitate produced per unit volume of urease solution gradually converged to a certain value. The shear strength (increased by 37.9%) and permeability (decreased by about 8.9-68.5%) of the modified desert sand peaked with the increase in fly ash content. The microscopic test results indicated that the fly ash could provide nucleation sites for the bio-cement, effectively improving the mechanical properties of the desert sand. The crystal types of calcium carbonate in the modified desert sand were calcite and aragonite, which were the most stable crystal types. This study provides innovative ideas for interdisciplinary research in the fields of bioengineering, ecology and civil engineering.

Despite efforts to reduce dependence on coal-fired power generation due to climate concerns, continued usage for energy stability is anticipated. This study was conducted to address environmental issues associated with coal-fired power generation and promote its persistent utilization. we aimed to establish both eco-friendly and economically sustainable practices by mitigating waste such as fly ash (FA) and bottom ash (BA) emissions while recycling them in circulating fluidized bed combustion (CFBC). Initially, we conducted a literature review to analyze the global and domestic trends in coal-fired power generation. Subsequently, we performed experimental research on CO2 crystallization as a multifaceted approach for treating exhaust gases and waste materials such as FA and BA simultaneously. Throughout this research, we implemented a simple process to ensure scalability. In the context of carbon capture, utilization, and storage (CCUS) technology, we conducted experimental research on mineralizing CO2 targeting FA and BA by applying ambient temperature, atmospheric pressure, and simulated exhaust gas. The empirical findings demonstrated that 12.28 kg CO2/ton and 58.14 kg CO2/ton of CO2 were immobilized for BA and FA, respectively. The economic evaluation was measured based on the experimental results obtained from the techno-economic analysis (TEA). The B/C ratio stands at 1.07, with the cost of composite carbonate estimated at USD 159.6 per ton. With an internal rate of return (IRR) of 7.78 % and a net present value (NPV) of USD 7294.59, the economic viability demonstrates considerable promise. Ultimately, this study aims to mitigate the impact of coal-fired power plants on climate change and enhance environmental sustainability through CO2 removal and waste recycling.

The effects of steel slag (SS) and fly ash (FA) on hydration heat, fluidity, setting time and rheological properties of alkali-activated slag (AAS) pastes with different silicate modulus (Ms) values were comparatively investigated. The results show that the incorporation of SS shortens the induction period, increases the cumulative hydration heat, improves the initial fluidity and decreases the setting time at low Ms, but the opposite trend is found at high Ms. FA significantly retards the reaction, reduces the hydration heat, increases the fluidity and prolongs the setting time. The addition of SS or FA reduces the yield stress and plastic viscosity of AAS paste. SS improves the rheological properties of AAS paste more significantly than that of FA at high Ms. The yield stress and plastic viscosity of AAS paste with SS or FA rise with the increasing Ms and decline with the increasing water/binder (w/b) ratio.

Aiming at the acid mine drainage (AMD) in zinc, copper and other heavy metals treatment difficulties, severe pollution of soil and water environment and other problems. Through the ultrasonic precipitation method, this study prepared fly ash-loaded nano-FeS composites (nFeS-F). The effects of nFeS-F dosage, pH, stirring rate, reaction time and initial concentration of the solution on the adsorption of Zn(II) and Cu(II) were investigated. The data were fitted by Lagergren first and second-order kinetic equations, Internal diffusion equation, Langmuir and Freundlich isotherm models, and combined with SEM, TEM, FTIR, TGA, and XPS assays to reveal the mechanism of nFeS-F adsorption of Zn(II) and Cu(II). The results demonstrated that: The removal of Zn(II) and Cu(II) by nFeS-F could reach 83.36% and 70.40%, respectively (The dosage was 8 g/L, pH was 4, time was 150 min, and concentration was 100 mg/L). The adsorption process, mainly chemical adsorption, conforms to the Lagergren second-order kinetic equation (R2 = 0.9952 and 0.9932). The adsorption isotherms have a higher fitting degree with the Langmuir model (R2 = 0.9964 and 0.9966), and the adsorption is a monolayer adsorption process. This study can provide a reference for treating heavy metals in acid mine drainage and resource utilization of fly ash.

Binders formulated with activated alkali materials to replace Portland cement, which has high polluting potential due to CO2 emissions in its manufacture, have increasingly been developed. The objective of this study is to evaluate the main properties of activated alkali materials (AAM) produced by blast furnace slag, fly ash, and metakaolin. Initially, binders were characterized by their chemical, mineralogical and granulometric composition. Later, specimens were produced, with molarity variation between 4.00 and 5.50, using the binders involved in the research. In preparing the activating solution, sodium hydroxide and silicate were used. The evaluated properties of AAM were consistency, viscosity, water absorption, density, compressive strength (7 days of cure), calorimetry, mineralogical analysis by X-ray diffraction, and morphological analysis by scanning electron microscopy. The results of evaluation in the fresh state demonstrate that metakaolin has the lowest workability indices of the studied AAM. The results observed in the hardened state indicate that the metakaolin activation process is optimized with normal cure and molarity of 4.0 and 4.5 mol/L, obtaining compressive strength results after 7 days of curing of approximately 30 MPa. The fly ash activation process is the least intense among the evaluated binders. This can be seen from the absence of phases formed in the XRD in the compositions containing fly ash as binder. Unlike blast furnace slag and metakaolin, the formation of sodalite, faujasite or tobermorite is not observed. Finally, the blast furnace slag displays more intense reactivity during thermal curing, obtaining compressive strength results after 7 days of curing of around 25 MPa. This is because the material\'s reaction kinetics are low but can be increased in an alkaline environment, and by the effect of temperature. From these results, it is concluded that each precursor has its own activation mechanism, observed by the techniques used in this research. From the results obtained in this study, it is expected that the alkaline activation process of the types of binders evaluated herein will become a viable alternative for replacing Portland cement, thus contributing to cement technology and other cementitious materials.

Chlorinated benzenes (CBzs) are a group of organic pollutants, which have been industrially or unintentionally produced through various chemical and thermal processes. Studies on full congener profiles of CBzs in waste and environmental samples are relatively limited and not updated. In the present study, concentrations of 12 CBzs were determined in fly ash (FA) and bottom ash (BA) samples collected from one municipal waste incinerator (MWI) and one industrial waste incinerator (IWI) in northern Vietnam. Levels of Σ12CBzs were higher in bottom ash (median 25.3; range 1.59-45.7 ng/g) than in fly ash (median 7.30; range 1.04-30.0 ng/g). The CBz profiles were dominated by di- and tri-chlorinated congeners with the major congeners as 1,2,4-TCB, 1,2,3-TCB, 1,2-DCB, and 1,3-DCB. However, CBz profiles varied greatly between sample types and incinerators, implying differences in input materials, formation pathways, and pollutant behaviors. Incomplete combustion is possibly responsible for high levels of CBzs in industrial bottom ash. The emission factors of Σ12CBzs ranged from 21 to 600 µg/ton for fly ash and from 190 to 4570 µg/ton for bottom ash, resulting in annual emissions of about 6 and 3 g/year for the IWI and MWI, respectively. Our results suggest additional investigations on industrial emission and environmental occurrence of all 12 CBzs rather than solely focusing on regulated congeners like hexachlorobenzene and pentachlorobenzene.

The multi-source hazardous waste co-disposal system, a recent innovation in the industry, offers an efficient approach for hazardous waste disposal. The incineration fly ash (HFA) produced by this system exhibits characteristics distinct from those of typical incineration fly ash, necessitating the use of adjusted disposal methods. This study examined the physicochemical properties, heavy metal content, heavy metal leaching concentration, and dioxin content of HFA generated by the new co-disposal system and compared them with those of conventional municipal waste incineration fly ash. This study investigated the solidification and stabilization of HFA disposal using the organic agent sodium diethyl dithiocarbamate combined with cement on a field scale. The findings revealed significant differences in the structure, composition, and dioxin content of HFA and FA; HFA contained substantially lower levels of dioxins than FA did. Concerning the heavy metal content and leaching; HFA exhibited an unusually high concentration of zinc, surpassing the permitted emission limits, making zinc content a critical consideration in HFA disposal. After stabilization and disposal, the heavy metal leaching and dioxin content of HFA can meet landfill disposal emission standards when a 1% concentration of 10% sodium diethyldithiocarbamate (DDTC) and 150% silicate cement were employed. These results offer valuable insights into the disposal of fly ash resulting from incineration of mixed hazardous waste.

Herein, the fabrication of electrospun nanocomposites, using polyacrylonitrile nanofibers (PNF) modified with nano-bentonite and fly ash, is explained. Further, the use of electrospun adsorbent for the remediation of Pb (II) ions from water has been explored. Pristine PNF and nanocomposites were characterized using SEM, EDX, and FTIR to analyze surface topology, elemental composition, and functional groups, respectively. The adsorptive behavior of developed adsorbents was investigated using the effects of dosage, initial concentration, time, and temperature. Pseudo-second order kinetics fit well with experimental data and the adsorption followed intra-particle diffusion. The thermodynamics study confirmed spontaneous endothermic adsorption of the heavy metal. Nanocomposites-based adsorbents showed improved adsorption capacity for Pb (II) ions compared to pristine PNF.

As governments around the world take on ambitious construction projects, from housing to infrastructure to transportation, the demand for cement is set to rise. It is anticipated that global cement production is set to achieve a compound annual growth rate of ∼5.1% for the years 2022-2025. The negative impact of cement production on the environment, such as carbon emissions and energy consumption, is also well known. This instigates the need to look for alternative and sustainable supplementary cementitious materials (SCMs) such as Fly ash (FA), Limestone (LS), Metakaolin (MK), Ground granulated blast furnace slag (GGBFS) and Silica fume (SF) which when blended with Portland clinker result in lower carbon emissions and better end products. With expanding cement demand, the need for chemical admixtures has also increased. This comprehensive study focuses on the compatibility of commercially available superplasticizers with SCMs blended low carbon cement and their influence on fresh and hardened properties along with microstructural and durability aspects. The chemistry of superplasticizers and how it effects the hydration mechanism of blended cement are also highlighted in detail. Moreover, the effect of different types of superplasticizers, their dosage, water binder ratio, and details of experiments used by other authors are also discussed and listed. As cementitious matrix containing any kind of SCM such as FA showed better environmental performance on the basis of life cycle assessment which was due to carbon emission factor (ξi). For cement, ξi was 311.27 kg CO2-eq/t, whereas for FA it was much lower (8.70 kg CO2-eq/t). Based on this comprehensive literature review, current challenges for the utilisation of waste SCMs incorporating superplasticizers along with research gap have been identified. Apart from this, the ongoing research work on the effect of chemical and mineral admixture on Limestone-calcined clay cement (LC3) using statistical modelling to optimize the mix is also discussed. It was observed that the use of a specific type of mineral admixture with a superplasticizer inversely affected the mechanical properties like compressive strength and modulus of rupture but improved the water-binder ratio, porosity, and water absorption.