CO_(2) mineralization by typical industrial solid wastes for preparing ultrafine CaCO_(3): A review

Mineral carbonation is a promising CO_(2) sequestration strategy that can utilize industrial wastes to convert CO_(2) into high-value CaCO_(3).This review summarizes the advancements in CO_(2) mineralization using typical industrial wastes to prepare ultrafine CaCO_(3).This work surveys the mechanisms of CO_(2) mineralization using these wastes and its capacities to synthesize CaCO_(3),evaluates the effects of carbonation pathways and operating parameters on the preparation of CaCO_(3),analyzes the current industrial application status and economics of this technology.Due to the large amount of impurities in solid wastes,the purity of CaCO_(3) prepared by indirect methods is greater than that prepared by direct methods.Crystalline CaCO_(3) includes three polymorphs.The polymorph of CaCO_(3) synthesized by carbonation process is determined the combined effects of various factors.These parameters essentially impact the nucleation and growth of CaCO_(3) by altering the CO_(2) supersaturation in the reaction system and the surface energy of CaCO_(3) grains.Increasing the initial pH of the solution and the CO_(2)flow rate favors the formation of vaterite,but calcite is formed under excessively high pH.Vaterite formation is favored at lower temperatures and residence time.With increased temperature and prolonged residence time,it passes through aragonite metastable phase and eventually transforms into calcite.Moreover,polymorph modifiers can decrease the surface energy of CaCO_(3) grains,facilitating the synthesis of vaterite.However,the large-scale application of this technology still faces many problems,including high costs,high energy consumption,low calcium leaching rate,low carbonation efficiency,and low product yield.Therefore,it is necessary to investigate ways to accelerate carbonation,optimize operating parameters,develop cost-effective agents,and understand the kinetics of CaCO_(3) nucleation and crystallization to obtain products with specific crystal forms.Furthermore,more studies on life cycle assessment(LCA)should be conducted to fully confirm the feasibility of the developed technologies.

Effects of acid-rock reaction on physical properties during CO_(2)-rich industrial waste gas(CO_(2)-rich IWG)injection in shale reservoirs

"Carbon peaking and carbon neutrality"is an essential national strategy,and the geological storage and utilization of CO_(2)is a hot issue today.However,due to the scarcity of pure CO_(2)gas sources in China and the high cost of CO_(2)capture,CO_(2)-rich industrial waste gas(CO_(2)-rich IWG)is gradually emerging into the public's gaze.CO_(2)has good adsorption properties on shale surfaces,but acidic gases can react with shale,so the mechanism of the CO_(2)-rich IWG-water-shale reaction and the change in reservoir properties will determine the stability of geological storage.Therefore,based on the mineral composition of the Longmaxi Formation shale,this study constructs a thermodynamic equilibrium model of water-rock reactions and simulates the regularity of reactions between CO_(2)-rich IWG and shale minerals.The results indicate that CO_(2)consumed 12%after reaction,and impurity gases in the CO_(2)-rich IWG can be dissolved entirely,thus demonstrating the feasibility of treating IWG through water-rock reactions.Since IWG inhibits the dissolution of CO_(2),the optimal composition of CO_(2)-rich IWG is 95%CO_(2)and 5%IWG when CO_(2)geological storage is the main goal.In contrast,when the main goal is the geological storage of total CO_(2)-rich IWG or impurity gas,the optimal CO_(2)-rich IWG composition is 50%CO_(2)and 50%IWG.In the CO_(2)-rich IWG-water-shale reaction,temperature has less influence on the water-rock reaction,while pressure is the most important parameter.SO2 has the greatest impact on water-rock reaction in gas.For minerals,clay minerals such as illite and montmorillonite had a significant effect on water-rock reaction.The overall reaction is dominated by precipitation and the volume of the rock skeleton has increased by 0.74 cm3,resulting in a decrease in shale porosity,which enhances the stability of CO_(2)geological storage to some extent.During the reaction between CO_(2)-rich IWG-water-shale at simulated temperatures and pressures,precipitation is the main reaction,and shale porosity decreases.However,as the reservoir water content increases,the reaction will first dissolve and then precipitate before dissolving again.When the water content is less than 0.0005 kg or greater than 0.4 kg,it will lead to an increase in reservoir porosity,which ultimately reduces the long-term geological storage stability of CO_(2)-rich IWG.

Preparation of Super Composite Cement with a Lower Clinker Content and a Larger Amount of Industrial Wastes

The effects of the grinding mode,fineness,gypsum kinds and dosage,mix proportions on properties of the composite cements consisting of slag,fly ash,limestone and a lower content clinker were investigated,respectively.The results show that when the proportions among slag,fly ash and limestone are appropriate,the grinding technology and system are reasonable,the optimized gypsums and additives are effective,the 52.5R grade cement (52.5R grade cement means a higher strength than 52.5 at early age) can be prepared by clinker dosage of 50% in weight,the 42.5R or 42.5,32.5 grade composite cement containing 40% and 30% clinker also may be made, respectively.Moreover,the high performance concrete prepared from the above composite cements was studied experimentally.

Industrial wastes applications for alkalinity regulation in bauxite residue: A comprehensive review

Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda.Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfilled,creating environmental risks either from the generation of dust or migration of filtrates.High alkalinity is the critical factor restricting complete utilization of bauxite residues,whilst the application of alkaline regulation agents is costly and difficult to apply widely.For now,current industrial wastes,such as waste acid,ammonia nitrogen wastewater,waste gypsum and biomass,have become major problems restricting the development of the social economy.Regulation of bauxite residues alkalinity by industrial waste was proposed to achieve‘waste control by waste’with good economic and ecological benefits.This review will focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste.It will propose key research directions with an emphasis on alkaline regulation by industrial waste,whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on bauxite residue disposal areas(BRDAs)following large-scale disposal.

The catalytic effect of the Na and Ca-rich industrial wastes on the thermal ignition of coal combustion

The catalytic effects of four industrial wastes,namely,the soap residue(SR),brine sludge(BS),calcium carbide residue(CCR),and white lime mud(WLM),on coal thermal ignition were investigated.The acidity of palmitate anion associated with Na+in SR was lower than that of chloride anion combined with Na+in BS,which resulted in an improved the combustion of SR.The acidity of OH-anion combined with Ca2+in CCR was lower than that of CO32-anion combined with Ca2+in WLM,resulting in CCR exhibiting a better catalytic effect on coal ignition.The alkaline metal Na had lower initial ionisation energy than the alkaline earth metal Ca.Therefore,the Na-rich SR exhibited higher catalytic activity on coal ignition than Ca-rich CCR.The ignition temperature of coal with 0.5%SR decreased from 544 to 503°C.

Preparation and characterization of high-strength calcium silicate boards from coal-fired industrial solid wastes

To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization(FGD) gypsum. The changes in mineral phases, chemical structure, and morphology during hydration were investigated by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), and scanning electron microscopy(SEM). A traditional board made from quartz and lime was prepared as a reference. The novel board not only consumes a lot of solid wastes, but also meets the strength requirement of the class-five calcium silicate board according to the Chinese Standard JC/T 564.2—2008. Microanalysis showed that hydrated calcium silicate gel(C-S-H(I)), ettringite, tobermorite, and xonotlite were successively generated in the novel board by synergistic hydration of the mixed solid wastes. The board strength was improved by the formation of tobermorite and xonotlite but decreased by unhydrated quartz. It was demonstrated that quartz was not completely hydrated in the traditional board. As a result, the flexural strength of the traditional board was much lower than that of the novel board.

Basic Characteristics of an Appropriate Waste Fillers for Solvent Free and Water-Borne Industrial Polymer Floors and Their Utilization

Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluents contained in the materials appeared at the end of 90´s.This situation was supported by the Council of Europe in 2004 to reduce VOC emissions to zero till 2020.Solvent materials were thus largely replaced by solvent free materials from which the volatile substances are not released into the air.But pressure continued to increase,and over the past decade began to take centre stage water-based epoxy.On the Czech market solvent based material is still occasionally used,but predominant are solvent free materials.There are no commonly used materials containing wastes as fillers in new water-borne and solvent-free epoxy materials.Characteristics identification of the waste material as a potential filler is a set of properties that determine the limits of secondary raw materials or waste as a filler.This paper describes the basic characteristics which must be selected to meet the requirements,to affect negatively the workability,sedimentation,properties and behavior of the final floor system.Some materials must comply with special requirements,such as resistance to chemicals,etc.Next part of paper talks about utilization of polymer floors and their mechanical properties.

Laboratory scale studies on removal of chromium from industrial wastes

Chromium being one of the major toxic pollutants is discharged from electroplating and chrome tanning processes and is also found in the effluents of dyes, paint pigments, manufacturing units etc. Chromium exists in aqueous systems in both trivalent (Cr 3+) and hexavalent (Cr 6+) forms. The hexavalent form is carcinogenic and toxic to aquatic life, whereas Cr 3+ is however comparatively less toxic. This study was undertaken to investigate the total chromium removal from industrial effluents by chemical means in order to achieve the Pakistan NEQS level of 1 mg/L by the methods of reduction and precipitation. The study was conducted in four phases. In phase Ⅰ, the optimum pH and cost effective reducing agent among the four popular commercial chemicals was selected. As a result, pH of 2 was found to be most suitable and sodium meta bisulfate was found to be the most cost effective reducing agent respectively. Phase Ⅱ showed that lower dose of sodium meta bisulfate was sufficient to obtain 100 % efficiency in reducing Cr 6+ to Cr 3+, and it was noted that reaction time had no significance in the whole process. A design curve for reduction process was established which can act as a tool for treatment of industrial effluents. Phase Ⅲ studies indicated the best pH was 8.5 for precipitation of Cr 3+ to chromium hydroxide by using lime. An efficiency of 100 % was achievable and a settling time of 30 minutes produced clear effluent. Finally in Phase Ⅳ actual waste samples from chrome tanning and electroplating industries, when precipitated at pH of 12 gave 100 % efficiency at a settling time of 30 minutes and confirmed that chemical means of reduction and precipitation is a feasible and viable solution for treating chromium wastes from industries.

Research Progress on Porous Ceramics Prepared from Industrial Solid Wastes

The situation of porous ceramics prepared from industrial waste slag(fly ash,red mud,metallurgical slag,tailings,etc.)was summarized.It was pointed out that the preparation of porous ceramics from industrial waste slag can bring long-term economic and social benefits.The development trend of secondary utilization of industrial waste slag was also prospected.

Behavior of Heavy Metals during the Agro-Industrial Wastes Gasification

The characterization analysis of three agro-industrial wastes was performed in order to study its thermal gasification. Some analyses such as determination of Ca, K and Mg concentration and determination of three representative toxic metals concentration Cd, Cr and Pb in all its oxidation states and the fundamental state, were carried out. The heavy metals concentration was also determined in the ashes obtained during the gasification process. The mobility of these elements was studied through three leaching tests. The behavior of heavy metals, sulfur and chlorine compounds, was predicted considering the presence of water vapor, syngas, Ca, Mg, K, Si, Al and other ash components. The heavy metals are not more concentrated in the gasification ash;these pollutants are released during this process. Ca, Mg and K presence in these residues would promote the pollutants retention. The ash of the studied waste can be disposed in controlled landfills or used in road construction, according to the obtained results during the leaching test DIN-DEV S4. The obtained results in the leaching test EPA 1311 TLCP classify these gasification ashes as no toxic waste.

Leaching kinetics in cyanide media of Ag contained in the industrial mining-metallurgical wastes in the state of Hidalgo, Mexico

The leaching kinetics in cyanide media of the silver contained in the Dos Carlos waste tailings at the City of Pachuca de Soto, Hidalgo State, Mexico were carried out. The used material contained the following chemical composition: 56 10-6of Ag, 0.6 10 6of Au and 70.43%(by weight) of SiO2; 7.032%(by weight) of Al2O3; 2.69%(by weight) of Fe; 0.46%(by weight) of Mn; 3.98%(by weight) of K2O; 3.34%(by weight) of CaO; 2.50%(by weight) of Na2O; 0.04%(by weight) of Zn; 0.026%(by weight) of Pb. The mineralogical phases present were the following: Silica, albite, argentite, berlinite, orthoclase, potassium jarosite, and natrojarosite. In the leaching kinetics in cyanide media, and under the studied conditions,the effect of the CN concentration on the reaction rate has no effect on the whole process of alkaline cyanidation, of which the reaction order is n 0. Temperature has an effect on the cyanidation rate of the reaction, with an activation energy of 47.9 KJ/mol. At the same time, when the particle size decreases there is an increase in the reaction rate, which is inversely proportional to the particle diameter; when increasing the NaOH concentration there is an increase in the reaction rate Kexp, with a reaction order(n) of 0.215 under the studied ranges.

Behavior of Cu, Pb, and Zn in Ash during the Endothermic Burning of Mixed Industrial Wastes

The behaviors of Cu, Pb, and Zn during the endothermic burning of heterogeneous wastes were investigated using a variety of operational parameters, i.e., the mixed waste ratio, burning temperature, and burning time, to obtain fundamental knowledge to generate an optimal burning operation and recycling strategy for bottom ash. Changing these parameters had no impact on the Cu content of the ash, whereas the Pb content depended on the burning temperature and the mixed ratio, and the Zn content was affected by all three parameters. It was found in this study that the optimal burning conditions were a temperature of 1100?C, a time of 15 minutes, and either the current waste conditions or waste conditions with double the waste plastic and wood content.

Biochemical changes during composting of coir pith waste as influenced by different agro industrial wastes

Coir pith, a byproduct of coconut husk is difficult to decompose due to its high lignin and cellulose content. In this study, coir pith was composted with different agro industrial by products such as cow dung, vegetable market waste, poultry waste and microbial consortium. The different treatment combinations used in the present study were Control, T1 (Coir pith + Cow dung + Vegetable market waste + Poultry waste + mixed microbial culture (Trichoderma viridae + Pleurotus sajar caju), T2 (Coir pith + Vegetable market waste + Poultry waste + Tank slit + Mixed microbial culture) and T3 (Coir pith + Cow dung + poultry waste + tank slit + mixed microbial culture). At the end of 12th week, in the treatment T1, C: N ratio of 21.8:1 was observed in the composted coir pith sample. Highest P content of 0.47% and K content of 1.2% and the least Cellulose and Lignin contents of 22.8% and 10.03% were recorded in the T1 treatment after a composting period of 12 weeks. Highest pH of 7.4 was observed in the treatment T3, this was followed by T1 (7.2) treatment.

A disposal strategy of industrial hazardous wastes in the Three Gorges Region

A large quantity of industrial hazardous wastes (IHWs) accumulates in the Three Gorges Region. This study found that approximately 15 000 t IHWs were piled in the region by October 2001. These IHWs came from various sources and were complex in composition, mostly toxic and difficult to be disposed. IHW is regarded as a potential threat to the ecological environment, water resources and survival of local residents. It is important and indispensable to dispose the waste properly. To meet the regulation requirements on the disposal of IHWs and to minimize environmental effects on the Three Gorges Region, a disposal strategy is proposed, according to which approximately 600 t of the IHWs can be disposed by chemical stabilization, incineration and other treatment measures, and the rest need be stockpiled in safe and reliable places situated above the 177 m impoundment line of the Three Gorges dam.

Quantification of Flavonoids in Brazilian Orange Peels and Industrial Orange Juice Processing Wastes

The flavonoid content in orange peels of different Brazilian citrus varieties such as bahia, lima, lima-of-persian, morcote, pera, ponkan, seleta, cravo, kinkan and pomelo was assessed. Industry processing juice wastes such as bagasse, bagasse residues, animal feeding bagasse, pulp WEUE and CORE-wash were also analyzed. The HPLC analysis indicates that the most abundant flavonoids found in these Brazilian citrus peels are hesperidin and naringin. The solvents used are selective for flavonoid extraction, and depending on their polarity, glycoside or aglycone flavonoids are extracted. The use of multivariate analysis shows that DMSO is the best solvent to extract glycosides flavanones while hexane displays high selectivity in the extraction of polymethoxylated flavones. The flavonoids present in the orange wastes, obtained at different stages of the industrial processing, are qualitative and quantitatively different. The identification and quantification of the flavonoid composition in each Brazilian citrus variety were evaluated and allowed the selection of the best solvent for the extraction of each specific class of flavonoids. These compounds were found to be more abundant in the fruit peels than in their juices, revealing their great industrial potential. The residual portion of the processing juices is also rich in flavonoids, depending on the processing step.

Gamma Radiation Hazards and Risks Associated with Industrial Wastes Materials

Solid wastes are generated from common manufacturing and industrial processes, and can also be caused by disposing commerce products. The natural radionuclide (238U, 226Ra, 232Th and 40K) concentrations in various solid waste samples were determined by using a high pure germanium detector. The obtained average concentration values of 226Ra, 232Th, and 40K in various solid wastes were: Iron (173.29, 141.99 and 32.68 Bq·kg-1), Copper (2.63, 0.60 and 30 Bq·kg-1), Aluminum (3.97, 4.89 and 41.67 Bq·kg-1) and in Wood (4.22, 3.11 and 30.20 Bq·kg-1), respectively. The total average values of radium equivalent and the absorbed dose rate were 95.87 Bq·kg-1 and 44.56 nGyh-1, respectively. The effective dose rates in outdoor and indoor average values were 0.05 and 0.20 mSvy-1, respectively. These health hazard parameters were considered to be below the safe limit of UNSCEAR 2000. The presented results show no significant radiological health risks for the workers in the industrial workshops and inhabitance health.

The Activity Concentrations, Radiation Contamination, and Hazards from Wastes and Soil Samples in Nasirabad Industrial Area, Chattogram, Bangladesh

Soils and other solid wastes from industrial areas of Nasirabad, Chattogram are usually dumped or used for land development. Information about the radioactivity level presented on these soil and wastes enables one to assess any possible radiological hazard to humankind by the use of such materials. A total of 37 (31 soils and 6 solid waste) samples near from different types of industries along four kilometre range were collected. The presence and activity concentrations of naturally occurred radioactive materials (NORM) and anthropogenic radionuclides in the samples were estimated using HPGe detector of 40% relative efficiency. The activity concentration of 226Ra, 232Th and 40K were found to be ranging from 8 ± 2 to 131 ± 18.33 with an average of 21 Bq·kg-1, 10 ± 2.69 to 133 ± 15.96 with an average of 40 Bq·kg-1 and 81 ± 22.68 to 930 ± 260.40 with an average of 449 Bq·kg-1 respectively. Besides this, some hazard indices like, the radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), and the activity concentration index (Iy) were calculated to assess the radiation hazard in this region. The averages of calculated hazard indices were within the normal limits, except the activity concentration index, which shows elevated values. The outcomes of this study could serve as important baseline radiological data for future epidemiological studies and environmental monitoring initiatives in the study area.

A Review on Stabilization of Expansive Soil Using Industrial Solid Wastes

In developing countries like India, Industrialization is rising rapidly, and also?a great paucity of land is there, the demand for exploitation of industrial?wastes?which coming from industries is increasing. From geotechnical perspective,?fly ash, granite and quarry waste, cement kiln dust, silica fume, rice husk etc.?are the waste materials?which?have effectual features requisites by an excellent soil stabilization admixture. Stabilization using solid wastes is one of the different?methods of treatment, to improve the engineering properties and make it?suitable for construction. This paper briefs about the recent trends in stabilization of expansive soil using industrial waste (granite and quarry waste, cement kiln?dust, silica fume, rice husk) as stabilizers for decreasing the environmental?hazards.

Biotechnological potential of agro-industrial wastes for protein enrichment by solid-state fermentation using Aspergillus niger

This study is to assess the biotechnological potential of agro-industrial wastes of pineapple(Ananas comosus),sweet potato(Ipomoea batatas)and watermelon(Citrullus lanatus)for protein enrichment by solid-state fermentation using Aspergillus niger.Spore suspensions of A.niger were prepared with potato dextrose broth that had been supplemented with sodium chloride,ammonium nitrate and thiamine,and adjusted to pH of 5.Initial protein contents of sterile and non-sterile wastes of the pineapple,sweet potato,and watermelon were determined by the Kjeldahl method.The remaining sterile and non-sterile wastes was inoculated with spore suspensions of A.niger and incubated at temperature of 24℃ under conditions of solid-state fermentation for 14 days.Protein contents of the inoculated sterile and non-sterile wastes were determined after 7 and 14 days.The sterile wastes of pineapple,sweet potato and watermelon recorded initial percentage protein contents of 4.37,4.39,and 10.89,respectively,whereas their corresponding non-sterile wastes recorded initial percentage protein contents of 3.76,4.00,and 10.16,respectively.The results further show that percentage increase in protein content of sterile wastes after 14 days of fermentation were pineapple,35.01%;sweet potato,27.60%;and watermelon,64.40%.Percentage increase in protein content of non-sterile wastes after 14 days of fermentation were pineapple,72.34%;sweet potato,85.25%;and watermelon,80.51%.These findings affirm the biotechnological potential of pineapple,sweet potato and watermelon wastes and the importance of fungi as agents for protein enrichment of agro-industrial wastes.

Potential industrial applications of photo/electrocatalysis: Recent progress and future challenges

Nowadays,the rapid development of the social economy inevitably leads to global energy and environmental crisis.For this reason,more and more scholars focus on the development of photocatalysis and/or electrocatalysis technology for the advantage in the sustainable production of high-value-added products,and the high efficiency in pollutants remediation.Although there is plenty of outstanding research has been put forward continuously,most of them focuses on catalysis performance and reaction mechanisms in laboratory conditions.Realizing industrial application of photo/electrocatalytic processes is still a challenge that needs to be overcome by social demand.In this regard,this review comprehensively summarized several explorations in thefield of photo/electrocatalytic reduction towards potential industrial applications in recent years.Special attention is paid to the successful attempts and the current status of photo/electrocatalytic water splitting,carbon dioxide conversion,resource utilization from waste,etc.,by using advanced reactors.The key problems and challenges of photo/electrocatalysis in future industrial practice are also discussed,and the possible development directions are also pointed out from the industry view.