Release Of Heavy Metals Research Articles

In-situ immobilization mechanism of lead and cadmium species by pyrolytic char in MSW pyrolysis process: Effect of chlorine group

The release of heavy metals brings severe environmental pollution and affects product application during the pyrolysis of municipal solid waste. Due to the excellent immobilization properties, the utilization of pyrolytic char for heavy metals is a promising approach, yet the microscopic mechanism between Cl functional groups on the char surface and Pb/Cd species remains unclear. Thus, density functional theory was applied to study the interaction mechanism between them through geometric optimization, electronic structure, and chemical reaction. Owing to the strong valence electron hybridization, the Cl functional group greatly increases the adsorption stability of Pb and Cd species. In addition, the armchair edge of char exhibits better affinity to heavy metal (belonging to the chemisorption) than that of the zigzag edge, whose fixation stability follows the order of Pb0>PbCl2>CdCl2>Cd0. Compared with the chlorination by HCl, the Cl group raises the chlorination barrier of Pb0 and Cd0 over the zigzag edge, while there is no apparent tendency over the armchair edge, since it increases the energy barrier of Cd0 but lowers that of Pb0. Therefore, the Cl functional groups of char promote the fixation of Pb/Cd and inhibit the generation of the easily leachable CdCl2, thereby facilitating the in-situ immobilization of heavy metals.

Risk control and assessment of sulfide-rich sediment remediation by controlled-release calcium nitrate

Nitrate stimulation is widely used in sediment remediation to eliminate sulfides, degrade organic pollutants and immobilize phosphorus. However, the environmental risks of nitrate escape and the subsequent release of pollutants (e.g. nitrite, ammonium and trace metals) to water bodies during its application has received less attention. In this study, controlled-release nitrate pellets (SedCaN pellets) were manufactured and applied at different sediment depths to examine their effectiveness in controlling the risk of nitrate escape and subsequent pollutant release. The germination of submerged plant was also analyzed to assess the ecological risks associated with the remediated sediment. The results showed that the SedCaN pellets slowly released calcium nitrate, which led to denitrifying sulfide oxidation, organic matter degradation and the immobilization of phosphorus as a calcium-bound species. Gas production by denitrification increased the sediment porosity (0.3–2.2%) and led to the concomitant release of nitrite, ammonium, and heavy metals, creating secondary risks. Application of the SedCaN pellets at depth decreased the nitrate escape and the secondary risks, presumably by means of a capping effect of the upper sediment. The release of nitrate, ammonium, Ni and Cu were partially limited by 91.6%, 19.0%, 61.6% and 57.4% when SedCaN pellets were incorporated into deeper sediments (7–9 cm). Moreover, the range of sulfide oxidation extended to the upper and lower sediments in the profile (column), while the sulfide oxidation efficiency reached 85.9–95.0%. Finally, increased germination of Bacopa monnieri (20.0–26%) demonstrated that in comparison to reference materials the ecological risks of the treated sediments was reduced and the habitat function of sediment was restored after nitrate-stimulating remediation. The results of this study provide valuable guidelines for nitrate-stimulating remediation of sulfide-rich (black-odor) sediments.

Concentrations, Speciation, and Potential Release of Hazardous Heavy Metals from the Solid Combustion Residues of Coal-Fired Power Plants.

Hazardous heavy metal-laden coal combustion byproducts exposed to precipitation or surface/groundwater are of environmental concern. This study analyzed fly ash (FA) and desulfurization gypsum (FGD gypsum) samples obtained from 16 coal-fired power plants in Guizhou Province, China. A combination of field and laboratory studies was used to investigate the binding forms of lead (Pb), cadmium (Cd), and chromium (Cr) and their leaching characteristics under natural storage conditions. The results showed that there were significant proportions of residual states of these elements in FA (84–99% for Pb, 83–91% for Cd, and 73–97% for Cr), indicating a lack of migration to other environmental media. FGD gypsum contained high proportions of metals in migratable states, but the environmental risks were low due to their very low concentrations. The release of Pb, Cd, and Cr from FA and FGD gypsum into extracts varied according to pH. This is related to the form of each element in the solid and the series of reactions that occurs during the leaching process. However, aside from Cr in FA, all heavy metals in FA and FGD gypsum samples were present in concentrations below the relevant standards for landfill leachate, indicating very low release rates. The Cr levels (206–273 μg/L) in some of the FA extracts were higher than the limits for water pollution from domestic landfill, indicating that Cr in FA poses a leaching risk. The results of field leachate sampling and indoor simulated rainfall experiments further validated these findings, indicating that the release of Cr from stockpiled coal FA is a cause for concern.

EVALUATION OF REMEDIATION ABILITY OF PONGAMIA PINNATA (L.) PIERRE UNDER HEXAVALENT CHROMIUM STRESS SOIL CONDITIONS

The increase in demands for industrial and mining products alters the conventional ecosystemapproach and attainment of sustainable development. Production of industrial products,processing of metals and protection of environment are intimately connected with one another andmake a challenge for sustainable growth and development of human-beings. In the industrial andmining environment, the release of heavy metals like hexavalent chromium [Cr(VI)] in solid,liquid or gaseous states influence the soil health of the region. Its concentration exceeding thethreshold limits is highly toxic and expresses in the form of manifold health problems. The healthof crop plants and animal husbandry are not spared from its toxic effects. The Cr (VI) is a highlytoxic, mobile, inter-convertible form of chemical element mostly used in industrial applications forits tensile strength and anti-corrosion ability. The soil pollution due to high Cr(VI) load is anegative attribute of mining and industrial developmental activities. Restoration of soil quality inthese mining and industrial areas is highly essential for sustainable development and healthyliving. Confinement of this toxic element in the closed biological system is a move towardsreducing its load in the soil profile. In the present approach Pongamia pinnata (L.) Pierre isexperimented as a renewable closed biological system for improving the soil health of Cr(VI) richmining and industrial sites. In this experimental set up the assessment of Cr(VI) content in selectedparts of this experimental plant species and the rhizospheric soil of their growth was performedusing the standard methodologies of APHA (1998). The positive aspect of this approach is thesurvival of this species under high soil Cr(VI) concentration and differential accumulation of thistoxic element in this biotic system. The targeted plant species was able to accumulateapproximately 50 % of the soil Cr(VI) within a period of 135 days from the initiation of treatment.The order of accumulation of Cr(VI) was found to be root > leaf > stem. Compared to thelimitations of physical, chemical and microbiological techniques, this process is sustainable in thelong run, cheaper and has least negative interference with other components of the environment.Further work in this area has the possibility to improve the efficiency of Cr(VI) intake by thisliving system.

Utilization of Demolition Waste for Treatment of Acid Mine Drainage and Immobilization of Heavy Metals Released from Copper Flotation Tailings

In this study, the treatment of acid mine drainage (AMD) and immobilization of heavy metals released from CFT (copper flotation tailings) were investigated using strongly alkaline demolition waste (DW), collected from the urban renewal areas. Shake flask batch tests were conducted to assess the influence of time and different ratios of CFT/DW on the acidity and heavy metal release characteristics of the drainage water. During the tests, samples were collected from filtered leachates at regular intervals to monitor pH, SO42- and release of heavy metals. The results indicated that the pH increased from 2.21 (t=0) to 10.37 after 120 minutes of shaking in an orbital shaker. The highest SO42- release ([SO42-]=4558 mg L-1, t=0) was measured at 1:3 dose of CFT:DW application with 257 mg L-1 (pH=10.37) at the end of 120 minutes. The addition of DW almost completely reduced the release of heavy metals from CFT due to its high alkaline content. As a result, it was suggested that DW could effectively be used for the treatment of AMD and immobilization of heavy metals released from CFT.

Biochar: its characteristics application and utilization of on environment

Abstract There are a variety of organic waste feedstocks that may be used to make biochar, such as agricultural byproducts and municipal solid waste. Biochar’s distinctive properties, such as its high carbon content and cation exchange capacity, large specific outer area, and stable structure, have attracted increased interest. The purpose of this study was to offer an overview of biochar with a focus on its environmental application by methodically analyzing and summarizing research on its production, characterization, modification, and the utilization in this review. Based on the kind of feedstocks used, the Biochar’s physiochemical characteristics might vary greatly. A variety of processes are used to create biochar, including pyrolysis, gasification, and hydrothermal carbonization. Acidic, alkaline, oxidizing agent, carbonaceous materials, steam and gas purging may be used to alter biochar. The environment field of application influences the adoption of modification methods. Soil remediation and improvement, carbon sequestration, composting of organic solid waste, water and wastewater purification, catalyst and activator, electrode materials and electrode modification are all examples of applications for biochar. In order to get consistent results, additional research into the use of biochar in carbon sequestration is needed. Soil microorganisms and biochar should be studied further to determine the primary cause of increased soil fertility in various soils and feedstocks. When biochar is utilized for environment remediation, further consideration must be given to the release of heavy metals and PAHs from biochar into the environment. To further understand how biochar works as an activator for per sulfate, more research into the link between biochar structure and activation capabilities is needed. There are several environmental remediation applications for biochar, and greater research is needed to understand its mode of action.

Mercury(II) and lead(II) ions removal using a novel thiol-rich hydrogel adsorbent; PHPAm/Fe3O4@SiO2-SH polymer nanocomposite.

The abundant release of toxic heavy metals into wastewater has been a serious threat to human health, aquatic environments, plants, and animals; thus, it is critical to purify wastewater of these pollutants through a proper treatment process. A novel hydrogel compound was synthesized using partially hydrolyzed polyacrylamide (PHPAm) and functionalized Fe3O4-coated magnetic nanoparticles (PHPAm/Fe3O4@SiO2-SH) that is efficient in removal of mercury and lead from wastewater. This new magnetic nanoadsorbent is characterized using scanning electron microscope, Fourier-transform infrared, thermogravimetric analysis, vibrating sample magnetometer, and energy-dispersive X-ray analysis. The central composite design under response surface methodology (CCD-RSM) was applied in designing the experiments to optimize the main parameters affecting the adsorption capacity: initial concentration (77.50 mg L-1), pH (6.11 and 6.48), adsorbent dosage (25 mg), and contact time (115 and 106 min) for both Hg2+ and Pb2+ adsorption, respectively. Quadratic models were used for variable predictions and analysis of variance was applied to evaluate the statistical parameters and investigate the interactions of the variables. The high determination coefficient (R2 0.99) for both metals indicates a good correlation between actual and predicted response values. Additionally, thermodynamic modeling showed an endothermic and exothermic for Hg2+ and Pb2+, respectively, and also the spontaneous nature of both metals' adsorption process within the temperature range of 288-318 K. Mercury and lead kinetic studies were in agreement with pseudo-second-order modeling, and the equilibrium results revealed that the Langmuir isotherm best fit the experimental data with maximum adsorption capacities of 256.41 and 227.27 (mg g-1) for Hg2+ and Pb2+, respectively. Overall, PHPAm/Fe3O4@SiO2-SH is thought to have highly promising potential for investigating heavy metals in wastewater treatment, and will make important contributions to similar studies that may be conducted in the future.

Identifying contamination of heavy metals in soils of Peruvian Amazon plain: use of multivariate statistical techniques.

The Peruvian Amazon plain has abundant natural resources and is home to great biodiversity, which makes it an area with high economic potential. However, the use of its resources through various activities has contributed to the release of heavy metals (HMs) into its soils, generating severe pollution problems which have mainly affected the health of local populations and their ecosystems. Currently, there are no comprehensive studies that have identified the specific sources of contamination by HMs in the soils of this part of the Peruvian territory. In this sense, this research aims to identify the possible sources of contamination by HMs in the soils of the Peruvian Amazon plain to focus efforts on the establishment of adequate measures for the protection of the health of people and the ecosystem. In the present study, samples of topsoils (0-20cm depth) and subsoils (100-150cm depth) were collected for the analysis of 11 HMs (Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn, Be, and Hg) in 48 sites located in four regions of the Peruvian Amazon plain (Loreto, Amazonas, San Martín, and Ucayali), over the year 2019. The enrichment factor and geoaccumulation index were applied to assess contamination levels of HMs. The results indicated that topsoils and subsoils presented a greater enrichment by the elements Be and Pb, and were classified as moderately contaminated. Likewise, the integral analysis of these indexes together with principal component analysis, hierarchical cluster analysis, correlation analysis, and coefficient of variation allowed the identification of potential sources of contamination by HMs. As a result, Fe, Co, Zn, Ni, V, and Cr were associated with natural or lithogenic sources (parent material, crude oil deposits, and organic matter decomposition). Hg was attributed to anthropogenic sources (illegal gold mining, atmospheric deposition, and vehicle emissions). Be, Pb, Cu, and Mn originated from natural sources (parent material, crude oil deposits, decomposition of organic matter, and forest fires) and anthropogenic (areas degraded by solid waste, illegal gold mining, agriculture, and hydrocarbons). These findings provide essential information to establish regulations and prevent and control HM contamination in soils of the Peruvian Amazon plain.

Heavy metal release and acid generation during the oxidation of sulfide waste rock induced by ferric iron

As aby-product of waste rock from sulfide ore, Fe3+ is one of the important factors that promote acid production and heavy metals release from waste rock pile fields. In this paper, the dynamic leaching tests were conducted to investigate the behavior of acid generation and heavy metal release from the sulfide waste rock of Dexing copper mine under different Fe3+ concentrations. The Sulphur content in the waste rock samples was 3.56 % and the net acid production potential (NAPP) reached 47.95 kg·t−1 H2SO4. Under the oxidation of 600 mg·L-1 Fe3+, the pH value of the leaching system decreased to 5.53, which is 1.85 units lower than that of the control check group (CK). However, the quantity of SO42- in the leachate was reduced by 41.81 % compared to the CK group, as the jarosite precipitation was more likely to form under high Fe3+ conditions. The oxidation of Fe3+ effectively accelerated the release of heavy metals from the waste rock. In addition, the heavy metals release quantity gradually increased with the increase of the Fe3+ concentration, with the maximum release quantities of Cu, Pb, Zn, and As of 569.69, 333.75, 222.69, and 31.11 μg·kg−1, respectively, which increased by 27.66 %-129.60 % compared to the CK group. The release of SO42-, Cu, Pb, and Zn was controlled by the combined internal diffusion and the chemical reaction, while the release of As was best fitted to the interfacial chemical reaction-controlled model. The SEM analysis showed that the waste rock near the top of the column was strongly corroded, resulting in the increase of the specific surface area of the waste stone by 24.48 %. The re-precipitation reaction of heavy metals mainly occurred near the bottom of the leaching column. Leaching under Fe3+ oxidation caused a decrease in the proportion of residual heavy metals in the waste rock, which will lead to the easier release of heavy metals.

Solvay claims soda ash breakthrough

Solvay is piloting a soda ash production process that it claims will reduce CO 2 emissions by half and eliminate limestone in its effluent, which currently contributes to the release of heavy metals into the sea. The company has reached a settlement with the activist investor Bluebell Capital Partners that calls for it to roll out the new process across all of its soda ash plants by 2050. In parallel, Solvay will take shorter-term measures to reduce the amount of limestone released into the sea from its plant in Rosignano, Italy. Solvay is the world’s largest producer of soda ash (sodium carbonate), which is used to make glass and other products. Solvay’s process uses brine and limestone as raw materials and ammonia as a catalyst. The process creates large amounts of CO 2 from the burning of fossil fuels and generates powdery limestone, which contains traces of heavy metals. The

Heavy metal and metalloid emissions during co-processing of waste in a sintering kiln: Migration characteristics in the kiln and long-term leaching from bricks

Heavy metals (HMs) in mixed hazardous waste can be volatilized in the kiln for preparing sintered bricks, which greatly increases the environmental risk. In this study, the volatilization, transformation, and leaching of HMs from bricks were evaluated. Field tests and laboratory leaching experiments were carried out. HM-contaminated soil was used to prepare sintered bricks at high-temperature in a tunnel kiln. Release of HMs from brick under rainfall conditions was investigated in laboratory simulation experiments. The field tests showed that the total amount of Pb, Zn, Cd distributed to the gas phase were all less than 2%, but the amount of Hg entering the gas phase 40.1%–60.5% in the particulate forms. The As leaching rate increased after sintering of bricks in the kiln, which was attributed to the increased formation of soluble arsenate and the reduced availability of sorption sites. The tank leaching test indicated that the release mechanism of trance elements (Cr, As, Zn, Cd, Pb and Ni) was mainly controlled by diffusion. This study provides useful knowledge for decreasing the volatilization and leaching of HMs from sintered bricks prepared using hazardous waste.

UV-vis spectroscopic method for detection and removal of heavy metal ions in water using Ag doped ZnO nanoparticles.

The primary source of heavy metal discharge into the water is human activity and urbanization near water bodies. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are Zinc (Zn), Copper (Cu), Nickel (Ni), Lead (Pb), Cadmium (Cd), Chromium (Cr), Arsenic (As), Mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals (Zhang et al., 2018; Lu et al., 2019; Ma et al., 2020; Gao et al., 2018; Wen et al., 2018; Saranya et al., 2021). Colorimetric sensing is a simple and cost-effective method for the detection of heavy metal ions. Moreover, the results can be analysed with naked eye. In this work, Ag doped ZnO nanoparticles synthesized via co-precipitation method are used for the colorimetric detection of heavy metal ions. The nanoparticles are characterized for their morphology, structural, and chemical analysis using XRD, SEM, EDS, and XPS techniques. The synthesized nanoparticles are used for the colorimetric detection of heavy metal ions. The heavy metal ions such as Ni2+, Cu2+, Cr3+, Cr6+, Fe2+, and Fe3+ are successfully detected and the color change is visible from the naked eye. The minimum concentration detected is found to be 100μM. The results are analysed via UV-vis spectroscopy. In addition to detection, the nanoparticles are further used as catalyst during the degradation of above detected heavy metal ions using NaBH4. All the heavy metal ions are degraded with in the duration of 30min. Thus, the Ag doped ZnO nanoparticles successfully detected the heavy metal ions in aqueous solution and also acted as a catalyst during their degradation.

Toxicity Assessment for Aquatic Ecosystem, Soil and Crops in Tongi, Bangladesh

As Tongi is an industrial area, massive amounts of effluents generated by the industries end up in the river and soil of this region. These wastes contain an excessive amount of heavy metals, which is detrimental for both environment and living organisms. The concentration of metals, Cadmium (Cd), Chromium (Cr), and Lead (Pb) were studied for water, soil and vegetable samples in order to understand the current pollution scenario of Tongi industrial area, Bangladesh. In this research, studies were conducted on water and soil by using water quality parameters, geo-chemical index, contamination factor, and pollution load index. This research also investigated the daily metal intake by people consuming the vegetables grown from that contaminated soil. Experimental observations reveal that the water of those areas is polluted with the concentration of Cd (0.0542-0.1728) mgL-1, Pb (0.0421-0.245) mgL-1 and Cr (1.0622-2.4357) mgL-1. However, the study also demonstrated that the soil of these areas is severely contaminated with Cd(4.42-100.564)mgkg-1, but moderately contaminated with Pb and Cr, and the rate of heavy metal intake is within the World Health Organization (WHO) standard among the consumers of vegetables grown in the local agricultural land. Cadmium concentration is observed to be higher in water and soil compared to the concentrations of lead and chromium, which might be due to the high cadmium containing industrial effluent discharge in the river. This study demonstrates the requirements for wastewater containing heavy metal discharge regulations into the river water, and it is also concluded that the assessment area is extremely contaminated with cadmium concentrations.

Impact of hydroxyl aluminum speciation on dewaterability and pollutants release of dredged sludge using polymeric aluminum chloride

Flocculation conditioning is a common pretreatment step for dredged sludge dewatering, while various pollutants in sludge might release into the residual water during flocculation conditioning and dewatering process, leading to secondary pollution. In this study, polymeric aluminum chloride (PAC) with different alkalinity was used as conditioners to enhance the dewaterability of dredged sludge in Baiyangdian Lake, and effects of hydroxyl aluminum speciation on dewatering performance and release of pollutants of dredged sludge were investigated. The results showed that the surface positive charge density of the mediumly polymeric hydroxyl aluminum (Alb) and highly polymeric hydroxyl aluminum (Alc) was higher, and the produced flocs were more compact, the abundant pore structure in flocs enhanced the water transport capacity and dewatering performance. Correlation analysis results showed that the release of heavy metals in residual water was mainly related to Ala, and the release of high molecular weight organic matter (aromatic protein), nitrogen and phosphorus was related to Alb, while Alc helped reduce pollutions in residual water. Alc showed better performance in improving dredged sludge dewaterability, and reduce the release of pollutants. This study provides an optimized strategy of flocculants for dredged sludge treatment based on aluminum speciation control.

Retention Effect of Heavy Metals in Rivers of a Typical Mountainous City by Cascade Weirs: A Case Study of Liangtan River in Chongqing

Contaminants such as heavy metals in rivers are partially retained in the sediments at the bottom as a result of the altered water regime within the cascade weirs. The associated heavy metals in the sediments can affect surface water quality and ecology for a long period. In May 2020, sediments were collected in a typical mountainous river (Liangtan River) with cascade weirs in the main urban area of Chongqing. The accumulation of sediments in each river section, the content of heavy metals, and other basic physicochemical indicators in the samples were monitored. The results showed that the average ω(As), ω(Cd), ω(Cu), ω(Hg), ω(Ni), and ω(Pb) in the sediments of the main stream of Liangtan River were (4.66±4.78), (0.361±0.256), (32.30±14.38), (0.069±0.039), (33.47±15.37), and (26.34±11.52) mg·kg-1, respectively. A large coefficient of spatial variation regarding the content of heavy metals in the sediments across the sampling sites was observed owing to the uneven spatial distribution of pollution sources and the destruction of river connectivity by cascade weirs. The modified geoaccumulation index (Im) showed that Cd was the most polluted heavy metal element in the sediments. Of the monitored river sections, 12.50% approached or were at moderate pollution levels, and these sections were mainly found in the upstream and downstream reaches of Liangtan River with relatively concentrated construction lands. The potential ecological risk assessment index method (RI) and the sediment quality guideline method (SQGs) showed that, in addition to Cd and Hg with a high pollution level and strong toxicity, Ni in the sediments also posed a potential threat to the ecological safety of surface water due to its high background content in the watershed. The total amounts of As, Cd, Cu, Hg, Ni, and Pb retained in the sediments by cascade weirs were estimated to be 446.10, 47.28, 4997.80, 10.81, 5135.68, and 4048.16 kg, respectively, in which Cd, Ni, and Pb were identified to be the major threats to the ecological safety of surface water over a long period. The upper reaches prior to the weirs with the most retained heavy metals and the easier formation of an anaerobic environment are suggested to be the key areas for investigation of the endogenous release of heavy metals. Source apportionment of heavy metals in river sediments through the combination of principal component analysis and cluster analysis revealed that Cd, Cu, and Pb mainly originated from residential/industrial point source pollution. Hg mainly originated from agricultural non-point source pollution, whereas As and Ni mainly originated from natural soil erosion.

Release of soluble ions and heavy metal during fly ash washing by deionized water and sodium carbonate solution

Two municipal solid waste incineration fly ashes were selected for washing by deionized water and Na2CO3 solution for comparison. Results showed that the benefits of washing were two folds: (1) Washing was able to reduce the contents of Cl− and SO42− while increased the contents of CaO, SiO2, Al2O3 etc.; (2) Washing by Na2CO3 solution showed increased stability of heavy metals (Cr, Ni, Cd, Cu, Zn and Pb) and fly ash was safe for later reuse. Release of Cl− was high at more than 90% regardless of washing solution. SO42− and Ca2+ removal was highly dependent on the dissolution and precipitation equilibriums. Na2CO3 washing promoted the formation of CaCO3. Thus SO42− was washed off instead of precipitating as CaSO4 and retained in fly ash solid. SO42− removal was raised to more than 80% by Na2CO3 washing as compared with about 30% by deionized water. At the same time, Ca removal by Na2CO3 dropped to 1–2%. In addition, the basicity of fly ash was important as high basicity helped SO42− removal. Overall, washing by Na2CO3 appears to be a promising option for fly ash treatment.

Study on the accelerated carbonation of MSWI fly ash under ultrasonic excitation: CO2 capture, heavy metals solidification, mechanism and geochemical modelling

The current carbonation technology of municipal solid waste incineration fly ash (FA) has disadvantages such as low carbon sequestration efficiency, harsh conditions, and complicated equipment. An ultrasonic chemical method coupled with wet-carbonization technology is proposed. The effects of the FA ultrasonic carbonation (UC) method on CO2 capture, heavy metals (HMs) release and solidification were investigated, and geochemical model of FA was explored. The results showed that UC improved the CO2 capture capacity, and the carbonation efficiency increased from 14.1 % to 18.8 % because the ultrasonic physical and chemical excitation improved the mass transfer efficiency and strengthened the gas–liquid-solid three-phase carbonation reaction. UC inhibited the release of Pb and Zn into the liquid phase (0.002 mg/L and 0.004 mg/L) and increased the solidification efficiency of Pb and Zn in FA (99.99 % and 100 %) because free Pb and Zn converted carbonates completely. UC FA had a single component, small particle size, high degree of homogenization, and contained slender nano-CaCO3 crystals. The acid neutralization capacities of original FA, FA4, and FA9 were 10, 8, and 3 meq/g because the carbonation reaction neutralized the alkaline substance. The content of carbonate minerals was the highest in UC FA and the pH of carbonate-minerals controlled dissolution/precipitation was mainly between 6 and 10. The HMs were in a soluble state (pH < 6) and the amphoteric HMs were affected by soluble hydroxides, the leaching concentration increasing (pH > 10). Therefore, UC FA had the potential of economical, environmentally friendly, and resource-based applications when avoiding strong acid and alkali application scenarios.

Black microplastics in the environment: Origin, transport and risk of tire wear particles

With the continuous growth of vehicle per capita in recent years, tire wear particles (TWP) produced by tire wear on roads have been widely found in various environmental media, whose environmental behavior and effects have attracted extensive attention. After being produced, these microsized and nanosized TWP will drift into the atmosphere or enter the surrounding soil, rivers, and even into the ocean with rain and runoff. The existence of TWP significantly affects the composition of organic materials in the environment. Meanwhile, the release of heavy metals and organic additives from TWP will be harmful to organisms and human health. We summarized the sources and characteristics of TWP, their migration and diffusion in water, atmosphere, and soil environment. By analyzing the environmental impacts and ecological risks of TWP pollution, we proposed the key questions urgently to be solved and prevention measures.

Biosorption - A Green Approach for the Sequestration of Cadmium and Chromium from Contaminated Water

The release of heavy metals from paint, electroplating, mining industries, etc. is a serious concern. Industrial effluents contain toxic heavy metals such as zinc, cadmium, chromium, lead, nickel, arsenic, etc. The sequestration of heavy metals by chemical processes is costly, time-consuming and causes environmental pollution. The use of microorganisms, example bacteria, actinobacteria, fungi, algae and yeasts for the sequestration of heavy metals is very eco-friendly, economical and fast. The work presented here describes the sequestration of cadmium and chromium from industrial effluent by bacteria Pseudomonas and Enterobacter sp. and fungi Aspergillus and Trichoderma sp. The industrial effluent was collected from Pimpri-Chinchwad, Pune, Maharashtra, India. The sequestration of Cd and Cr was less by Pseudomonas sp. which was 0.44 and 0.27 mg g-1 with biomass conc. (0.5 g). The sequestration of Cd and Cr byTrichoderma sp. was 0.51 and 0.36 mg g-1 respectively with biomass conc. (0.5 g). The biosorption is a 'green technology' for the sequestration of heavy metals from industrial effluents, waste water, and other contaminants.

Assessing the impact of different salinities on the desorption of Cd, Cu and Zn in soils with combined pollution.

Exploring the relationships between heavy metal release and salinity can help address the problems of combination of toxic heavy metals and salinization in contaminated soils. Therefore, in this study, the release characteristics of heavy metals (Cd, Cu and Zn) under different salt types and mass concentrations were investigated through batch desorption experiments. Spearman's correlation analysis was performed to assess the effects of typical physicochemical properties on metal release under salt stress. The results indicated that the types and concentration gradients of salt had notably different impacts on the release of different metals; specifically, there were significant impacts for Cd but slight impacts for Cu and Zn. MgCl2 and CaCl2 had more obvious promoting effects on Cd release, followed by a salt mixture and NaCl, and this pattern was similar for Zn release. Most salts could slightly restrain the release of Cu, except for MgCl2 and Na2SO4, which had slight promoting effects. Moreover, low levels of CaCl2 could effectively restrain the release of Cu. The results showed that the release capacities of metals followed the order of Cd > Cu > Zn, possibly attributed to the competitive adsorption among cations. Ferromanganese oxides in the soil favored the release of Cd and Zn under salt treatments, and redox potential was an important factor affecting Cu release. The results also suggested that the background values of metals could affect metal release, but the effects were varied under different salt treatments for Zn. The reason for this may be that the addition of different salts changed the effects of certain soil properties on the metal release. Overall, this study can serve as an important reference for controlling heavy metal pollution in soils in salinization and coastal areas.