Large Amounts Of Heavy Metals Research Articles

Evaluation of Germination and Early Seedling Growth of Different Grasses Irrigated with Treated Mine Water

Coal mining is known to have negative impacts on the environment, necessitating land rehabilitation after mining activities. Amongst the problems associated with coal mining is the accumulation of acid mine drainage characterized by large amounts of heavy metals and high acidity. The impact of these environmental problems on the ecosystem around mining areas underscores a need to devise strategies that will ensure sustainable restoration of the ecosystem integrity to ensure environmental protection. Of these, treatment of acid mine drainage using calcium sulfate dihydrate, which is subsequently used for irrigation during phytoremediation, holds great promise for restoration of open-cast mines. However, although grasses are used for rehabilitation of coal mined areas, the impacts of treated mine water on the germination, seedling emergence, and plant growth of grasses are not well known. The aim of the study was to evaluate the germination and early seedling growth responses of different forage grasses to treated mine water. Seven forage grass species were selected, with four species represented by two varieties while others were represented by one variety, totaling 11 forage grasses. For each plant entry, 100 seeds were placed in J.R. Petri’s dishes lined with Whatman No. 2 filter paper and watered with distilled and mine water to assess germination. For the seedling establishment experiment, only five species were studied, in which twenty seeds per species were sown in pots containing mine soil and irrigated using distilled and treated mine water. The final germination percentage (FGP), germination rate index (GRI), corrected germination rate index (CGRI), and T50 were determined for the germination trail and total biomass was assessed for the seedling growth trail. The highest FGP for all grasses was attained under controlled conditions, using distilled water, ranging from 38–94%. All grasses germinated when watered using treated mine water and had a FGP ranging from 20–91%. Relative to distilled water, GRI and CGRI were highest only for L. multiflorum cv AgriBoost when seeds were watered using the treated mine water. All grasses watered with treated mine water produced high biomass for the first two weeks, after which biomass production started to decline. Two grasses, Eragrostis curvula cv Ermelo and Lolium multiflorum cv Archie, showed tolerance to treated mine water irrespective of its high electrical conductivity (557 mS∙m−1). Therefore, these grasses could be used in the rehabilitation of coal-mined areas irrigated with treated mine water.

Source-specific ecological risk analysis and critical source identification of heavy metal(loid)s in the soil of typical abandoned coal mining area

Long-term coal mining activities in abandoned coal mining areas have resulted in the migration of large quantities of heavy metals into the surrounding soil environment, posing a threat to the regional ecological environment. This study focuses on the surface soil collected from a typical abandoned coal mining area. Methods such as the pollution index (PI) and potential ecological risk index (RI) were used to comprehensively evaluate the pollution levels and ecological risks of soil heavy metals. Geostatistical analysis and the APCS-MLR model were used to quantify the sources of soil heavy metals, and Nemerow integrated ecological risk (NIRI) model was coupled to apportion the ecological risks from different pollution sources. The results indicate that the average concentrations of Cd, As, and Zn are 4.58, 2.44, and 1.67 times the soil background values, respectively, while the concentrations of other heavy metals are below the soil background values. The soil of study area is strongly polluted by heavy metals, with the pollution level and ecological risk of Cd being significantly higher than those of other heavy metals. The NIRI calculation results show that the overall comprehensive ecological risk level is considerable, with sample points classified as relatively considerable, moderate, and low at 60.53 %, 36.84 %, and 2.63 %, respectively. The sources of soil heavy metals can be categorized into four types: traffic activities, natural sources, coal gangue accumulation, and a combined source of coal mining and agricultural activities, with contribution rates of 35.3 %, 36.1 %, 19.5 %, and 9.1 %, respectively. The specific source ecological risk assessment results indicate that coal gangue accumulation contributes the most to ecological risk (36.4 %) and should be prioritized for pollution control, with Cd being the priority control element for ecological risk. The findings provide theoretical support for the refined management of soil heavy metal pollution in abandoned coal mining areas.

Lead Tolerance and Remediation Potential of Four Indocalamus Species in Lead-Contaminated Soil.

Indocalamus plants are low-growing shrubby bamboos with growth advantages, such as high biomass and strong resistance, and they are rich in germplasm resources in southern China. This study conducted soil lead (Pb) stress experiments on Indocalamus latifolius (Keng) McClure (LA), Indocalamus hunanensis B.M. Yang (HU), Indocalamus chishuiensis Y.L. Yang and Hsueh (CH) and Indocalamus lacunosus Wen (LC). Five Pb treatments (0, 500, 1000, 1500 mg·kg-1 Pb, and 1000 mg·kg-1 Pb + 1000 mg·kg-1 ethylenediamine tetraacetic acid (EDTA)) were established. EDTA was applied to explore the tolerance mechanism of different Indocalamus species after absorbing large amounts of heavy metals. The results were as follows: (1) under Pb treatment, the total relative biomass of LA, HU and LC was <100%, whereas the total relative biomass of CH was >100%; (2) after applying EDTA, the bioconcentration coefficient, translocation factor, and free proline content of the four Indocalamus species increased; and (3) the Pb mobility and distribution rates of the underground parts of the four Indocalamus species were consistently greater than those of the aboveground parts. The Pb mobility and distribution rates in the stems increased after applying EDTA, while those in the leaves decreased, as the plants tended to transfer Pb to their stems, which have lower physiological activity than their leaves.

Comparison study of three universal methods for the recovery and purification of valuable heavy metals from electroplating sludge

The large amount of heavy metals from waste electroplating sludge has great recovery and treatment value, which is of great significance for environmental protection, resource recycling and sustainable development. In actual process, metals were relatively easy to be extracted from sludge, but the separation process was more complex. In this study, three universal methods for extracting low-grade and complex heavy metals from electroplating sludge (actual solid waste sample from Zhejiang Province, China) in terms of Selective ammonia treatment process (SAP), efficient acid treatment process (EAP) and roasting-acid treatment process (RAP) were investigated. In comparison, EAP was more advanced in extracting heavy metals from actual samples than SAP and RAP. It was noticed, by optimizing the separation and purification process, when the acid concentration was 5 % and the liquid–solid ratio was 10:1 with the assistance of effective extractants of Lix984N and P507, the purity and recovery rates for both copper and zinc products could reach to over 90 %, meanwhile, more than 80 % recovery rates of nickel products could be obtained. And compared with some existing related studies, the research process has the advantages of simpler operation mode and better separation effect, which offers the valuable insights into efficient separation and recovery of heavy metal resources from electroplating sludge. The methodology employed in this work can be easily applied to other solid/hazardous waste extraction processes.

Critical assessment and recommendations for sewage sludge management in Poland

The purpose of the article is to demonstrate practices used to supervise the use of sewage sludge for agricultural purposes. The presented research and conclusions are a trend analysis and are not to be used to penalise entities. Sewage sludge, which comes from the illegal dumping of wastewater into municipal wastewater by industrial plants, contains large amounts of heavy metals. Treatment plants transfer the sludge for agricultural use. Regulations specifically restrict the mode and conditions for such use of sludge. Methods: the research was carried out using a proprietary questionnaire, which is a supplement to the reporting questionnaire of the National Urban Wastewater Treatment Program implemented by the State Water Company "Wody Polskie". Results: The survey was conducted at 208 wastewater treatment plants in Poland. The results show that the majority of wastewater treatment plants do not properly supervise the process of introducing sewage sludge into the soil. They also lack supervision of how much heavy metals from wastewater are introduced into the soil. This means that there is a very high risk of contamination of agricultural soils. The results obtained could initiate a detailed analysis of this phenomenon in Poland. A comprehensive study of the scale of the practice and its current effects is required to determine the actual condition of soil treated with sewage sludge.

DYNAMICS OF HEAVY METALS MIGRATION IN THE SOIL AS A CONSEQUENCE OF MILITARY ACTIONS

The military operations in Ukraine have consequences for the biosphere, which is negatively affected by the hostilities, causing its destruction and degradation, - soils. It is currently impossible to fully assess the impact of military and terrorist actions on the environment due to the lack of accurate information. The shelling of civilian and strategically important objects in Ukraine created synergistic conditions for the environment to accumulate and enter through leaching from the soil a large amount of heavy metals into surface water. Accordingly, this leads to mass degradation of not only the soil environment, but also the hydrosphere and plant life. The entry of potentially toxic elements (PTE) into the environment, soil and plants is accompanied by their oxidation and other chemical processes. Soil sampling was carried out by the method of a concentric circle, in the canter of which is the source of pollution, which allows us to assess the degree of distribution of potentially toxic elements depending on the depth of the well. In our research on the content of heavy metals in the soil during the shelling of Lviv and 6 months later, XRF and ICP analyzes of soil samples. The results of the analysis of the content of heavy metals in the soil after 6 months show that the concentration of cadmium is reduced by two times; copper and nickel, respectively, 3 and 3.5 times; lead+ and chromium - twice. It is known that heavy metals do not undergo decomposition processes, but can only be redistributed between natural environments. They tend to concentrate in living organisms, causing various pathologies.

Toxic metals in water and soil

Industrialization and the development of modern civilization in general brought with it large amounts of heavy metals that were dispersed in the environment. Rapid screening technology for the detection of major and trace elements as well as heavy metals in various environmental samples was the goal of our research in this very topical area from an ecological and human health point of view. In this sense, the objectives of this study were to determine the limits of detection, accuracy, repeatability, selectivity and efficiency of different analytical methods in elemental analysis, especially traces of toxic elements. To assess the state of the environment, it is necessary to carry out a complete analysis of microelements using different analytical methods, as well as the preparation of samples, especially soil. Heavy metals that are extremely toxic are arsenic, lead, mercury, cadmium, chromium, copper and nickel, and given their extremely negative impact on human health, and mutation and lethal outcomes, their concentration in environmental samples must be accurately and precisely measured, especially in its primary components, water, soil and air. The aim of the measurement is to monitor, control and determine the presence of pollutants, but also to identify sources of pollution that threaten the living environment, the living world and, ultimately, humans, the last in the food chain.

Stabilization effect of chelating agents on heavy metals in two types of municipal solid waste incineration fly ash

Municipal solid waste incineration (MSWI) fly ash is complex in composition and contains large amounts of heavy metals. To investigate the effects of different passivating agents on Cd, Pb, Cr, Ni and Zn in different types of fly ash, 7 reagents were selected as passivating agents, including 3 inorganic reagents (Na2S, Na3PO4, NaH2PO4) and 4 organic reagents (SDD, DDTC, TMT, thiourea). The results showed that at low addition levels, sulfur-containing organic chemicals and phosphates were more effective in chelating these metals in both grate furnace incineration fly ash (GF FA) and circulating fluidised bed incineration fly ash (CFB FA), while Na2S was more effective in chelating heavy metals in CFB FA. In addition, agents containing -N-CS groups showed better chelation of heavy metals in GF FA, while heavy metals in CFB FA were more affinity to agents containing -SH groups. The ternary compound TMT-NaH2PO4-SDD (m1:m2:m3 = 2:3:1) was an excellent chelating agent for Pb, Cd in the GF FA, and TMT-Na2S-thiourea (m1:m2:m3 = 2:1:3) was a suitable chelating agent for these metals in CFB FA. The chelation rate of Cd and Pb after the treatments mixed ternary reagents was above 99%, and the leaching amount was much lower than the limit value of pollution control standards for domestic landfills. Moreover, under different pH leaching conditions, the leaching concentrations of Cd and Pb in the fly ashes treated with the ternary mixture were lower than the standard limits. In general, the ternary compound can effectively chelate heavy metals in fly ash, which provides a reference for selecting a suitable stabilizer combination for heavy metal in fly ash.

Comparative Study of Mercury in Canned and Fresh Indian Oil Sardine Sardinella longiceps

Essential and non-essential heavy metals are two categories for heavy metals. Small amounts of essential heavy metals are required by the human body to ensure its proper operation. High concentrations can become hazardous and change how the biochemical mechanisms that keep the human body functioning normally. The human body does not require non-essential heavy metals like mercury (Hg), which can be harmful to human health. Mercury can come from both natural and anthropogenic sources. When polluted soil and organisms are consumed by aquatic species, mercury bioaccumulates in their tissues, and its concentration rises up the food chain. Within the marine ecology, fish are at the top of the food chain. The aquatic food chain often starts with fish, and fish organs and tissues are at the top of the hierarchy and accumulate large amounts of heavy metals. In particular, the liver, kidney, and gill organs store metals (loids) at the highest level, and this varies depending on the type of metal; nonetheless, muscle is extensively examined as it is the main part of fish consumed by people. The muscular tissue of canned and fresh Indian oil sardines (Sardinella longiceps) was examined in the current investigation to determine the buildup of mercury there. Utilising a spectrophotometric analytical approach, stannous chloride was used for the analysis. Mercury levels in canned and fresh sardines were found to be 0.09 and 0.10 ppm, respectively. Sardines have a known Hg concentration of 0.04-0.18 ppm at the non-predator trophic level worldwide, which is also the level at which sardines may be consumed. Thus, the present sardines under study from Mumbai region are found to be suitable for consumption.

Lake Sediment Archive Reveals a Distinct Response to Anthropogenic Pb and Zn Deposition with Historical Periods: Pb-Zn Isotope Evidence.

Anthropogenic activities release large quantities of heavy metals into the atmosphere. In China, the input of these heavy metals through local and trans-boundary atmospheric deposition is poorly understood. To assess this issue, herein, we use Pb and Zn isotopes to constrain the sources of Pb and Zn in a 210Pb-dated sediment core collected from the enclosed lake in South China. We observed a progressive shift toward higher 208Pb/206Pb and Pb fluxes (0.79-4.02 μg·cm-2·a-1) from 1850 to 1950 and a consistent decrease in δ66ZnIRMM (as low as -0.097 ± 0.030‰) coupled with an increase in Pb (1.74-3.36 μg·cm-2·a-1) and Zn (8.07-10.44 μg·cm-2·a-1) fluxes after 1980. These distinguished isotopic signals and flux variations reveal the presence of trans-boundary Pb since 1900, with the addition of local industrial Pb and Zn pollution after 1980. Up to 72.3% of Pb deposited at our site can be attributed to long-distance transportation from previously industrialized countries, resulting in a noteworthy legacy of Pb in China since 1900. Despite the phasing out of leaded gasoline, Chinese gasoline still contributes an average of 20.9%. The contribution of China's mining and smelting activities to Pb has increased steadily since 1980 and remained stable at an average of 25.1% since 2000.

Analisis Pengaruh Kapur Tohor (CaO) dan Tawas Terhadap Parameter TSS dan pH di Desa Huta Dame Kecamatan Penyabungan Utara Kabupaten Mandailing Natal

The people's gold mining activities in Huta Dame Village, Kotanopan Utara District, Mandailing Natal are still very simple. The purpose of this study was to analyze the TSS and pH parameters around the gold mining area so that they comply with quality standards. This research method is by interviews and direct observation to the field. The results of the analysis showed that the quality of acid mine drainage before treatment was 4.26 and after the addition of quicklime in 1 gram it was still acidic but in the addition of quicklime in the 65th minute (3 grams) a pH of 6.02 was obtained and it met the quality standard. The addition of 1 and 3 grams of alum is still acidic and this can cause the air in the mining environment to be corrosive due to the large amount of heavy metals originating from rocks which can cause environmental damage, due to excessive use of mercury resulting in the emergence of acid mine drainage. The addition of 1 and 3 grams of quicklime, TSS values 48 &amp; 38 mg/l . The TSS values for the addition of 1 &amp; 3 grams of alum were 20 &amp; 28 mg/l and met the quality standards. Thus the use of quicklime in gold mining waste is more effective than the use of alum as an acid mine drainage treatment method.

Evaluation of the ability of cement prepared with incineration fly ash to solidify heavy metals at high temperatures

Scholars have demonstrated the feasibility of using incineration fly ash to prepare cement. Therefore, this article evaluated the performance changes and the ability to solidify heavy metals of cement prepared with the incineration fly ash after being exposed to fire (high temperature). The research results indicated that with the increase of incineration fly ash content, the mass loss of the cement prepared rose from 8.96% to 9.92%, and the strength loss increased from 63.91% to 92.73% after high-temperature treatment at 800 °C. Which proved that the incineration fly ash significantly weakened the performance of the cement after high temperatures, which was not conducive to the reuse of the components in cement. After high-temperature treatment, new phases - Lime and Tobermorite were generated, and the pore structure of cement was greatly changed, with a decrease in harmless pores. The content of harmful and multi-harmful pores exceeded 87%. A large amount of heavy metals evaporated, resulting in a decline of heavy metal content in cement. The leaching concentration of a few heavy metals in weak acid environments tended to increase, but it was still far below the limits specified in Chinese standards GB 5085.3-2007, GB 16889-2008, and GB 18598-2019. Therefore, the high-temperature treated cement still effectively solidified residual heavy metals, but it could not suppress the volatilization of heavy metals at high temperatures.

Physicochemical, Biochemical and Genotoxic Profile of Subchronic Exposure of Wister Rats to Treated Crude Oil Exploration Water

Background: Crude oil exploration water is the major waste product generated from petroleum exploration and production activities and is known to be a complex composition of numerous hazardous chemicals, including large quantities of heavy metals, inorganic, and organic substances and naturally occurring radioactive materials (NORMs).&#x0D; Objectives: This study was designed to investigate the physicochemical, biochemical and genotoxic profile of subchronic exposure of Wister rats to treated crude oil exploration water (TCOEW).&#x0D; Materials and Methods: Fifty rats were randomly assigned to five treatment groups, with ten rats per group, and treated with five concentrations (1%, 5%, 10% and 20%) of TCOEW. Each TCOEW concentration was administered for 90 days ad-libitum as normal drinking water to each group, while the control group was given tap water. Blood, liver, kidney, thymus, spleen and femoral bone of the animals were collected at the end of exposure for biochemical and histological assessments. The pH, conductivity, and turbidity were carried out on-site, while other physicochemical parameters were determined using standard laboratory methods. Data were analysed using descriptive statistics and ANOVA at α 0.05.&#x0D; Results: Treated crude oil exploration water caused a significant (p &lt; 0.05) increase in RBC, PCV and Hb while other hematological and biochemical parameters showed no difference. Also, TCOEW cause a significant increase in polychromatic erythrocytes (PCEs) in genotoxicity test and no major lesion were seen in the histopathology studies. Treated Crude Oil Exploration Water does not comply with FEPA standards of produced water due to high conductivity, salinity and total dissolved solid of the sample. The marked increase in micronuclei polychromatic erythrocyte formation (MNPCE) showed that TCOEW might be genotoxic and this could be responsible for the significant increase RBC, parked cell volume (PCV) and hemoglobin (Hb) observed.&#x0D; Conclusion: Although TCOEW does not totally meet FEPA standard for effluent discharge, it has mild genotoxic effect.

Phytoremediation of Heavy Metal Contaminated Soils Using Various Flower and Ornamentals

Soil contamination has become a serious problem in many industrialized and developing countries. Indiscriminate dumping of urban and industrial effluents along with solid waste often lead to toxic accumulation of heavy metal ions which not only impair soil productivity but also cause health hazards by entering into food chain via soil-plant-animal/human route. With rapid urbanization and industrialization, large quantities of industrial effluents get mixed with sewage and river water [1]. Irrigating crop fields with such contaminated sewage water is being increasingly adopted by marginal farmers due to scarcity of irrigation water. It also inadvertently leads to addition of large quantity of heavy metals to the agro ecosystem [2]. Plants with abilities to hyperaccumulate, accumulate, exclude and indicate heavy metals are important in environmental remediation. Most phytoremediation studies are aimed at inorganic pollutants through different approaches defined as phytoextraction (the used of metal accumulating plants to transport and concentrate metals from the soil to roots and above ground biomass), rhizofiltration (the use of plant roots to absorb, precipitate, and concentrate toxic metals from polluted effluents), and phytostabilization (the use of plants to reduce the mobility of metals)

Bio-transfer and bioaccumulation patterns of heavy metals in mine site-inhabiting ants and grasshoppers, across mine site restoration chronosequence.

Soil is known to serve as a significant sink for heavy metals in coal mine sites, thus also influence the plant and other organisms of that area. Hence, the presence of heavy metals in coal mine soil is of concern to land managers. Insects occupy different trophic positions in the food chains, thus many insect species accumulate large amounts of heavy metals in their bodies and this is a matter of concern. In the present study, we investigated biotransfer and bioaccumulation of heavy metals from soil, grass species Cynodon dactylon, Vetiveria zizanioides, grasshopper species Gastrimargus africanus, Choroedocus robustus, ant species Cataglyphis longipedem and Camponotus compressus in six different ages (2, 4, 6, 8, 10 and 12 year old) of coal mine sites. Our study revealed that at some extent the heavy metal content and BAF patterns of heavy metals along different pathways (from soil to grass, soil to grasshoppers and from grass to grasshoppers) were not consistent and did not reflect the soil pollution status for all the metals, related to the mine spoil dump age. However, in contrast, ants successfully reflected a consistent pattern in the bioaccumulation of heavy metals via soil, thereby indicating the pollution status of the soil along with the restoration age of mine spoil dumps. Our study showed that ant species can successfully forecast the presence of heavy metals of coal mine spoils along with their restoration.

Responses of rhizosphere microbial community structure and metabolic function to heavy metal coinhibition.

Metal mineral mining results in releases of large amounts of heavy metals into the environment, and it is necessary to better understand the response of rhizosphere microbial communities to simultaneous stress from multiple heavy metals (HMs), which directly impacts plant growth and human health. In this study, by adding different concentrations of cadmium (Cd) to a soil with high background concentrations of vanadium (V) and chromium (Cr), the growth of maize during the jointing stage was explored under limiting conditions. High-throughput sequencing was used to explore the response and survival strategies of rhizosphere soil microbial communities to complex HM stress. The results showed that complex HMs inhibited the growth of maize at the jointing stage, and the diversity and abundance of maize rhizosphere soil microorganisms were significantly different at different metal enrichment levels. In addition, according to the different stress levels, the maize rhizosphere attracted many tolerant colonizing bacteria, and cooccurrence network analysis showed that these bacteria interacted very closely. The effects of residual heavy metals on beneficial microorganisms (such as Xanthomonas, Sphingomonas, and lysozyme) were significantly stronger than those of bioavailable metals and soil physical and chemical properties. PICRUSt analysis revealed that the different forms of V and Cd had significantly greater effects on microbial metabolic pathways than all forms of Cr. Cr mainly affected the two major metabolic pathways: microbial cell growth and division and environmental information transmission. In addition, significant differences in rhizosphere microbial metabolism under different concentrations were found, and this can serve as a reference for subsequent metagenomic analysis. This study is helpful for exploring the threshold for the growth of crops in toxic HM soils in mining areas and achieving further biological remediation.

Trace elements in aquatic products from Shenzhen, China and their implications for human exposure

Aquatic organisms in industrially polluted areas can accumulate large quantities of heavy metals. To assess the resulting health risks, 11 trace elements in 184 aquatic products representing 14 species of fish, crustaceans, and bivalves collected from Shenzhen, China were determined. Aluminum (Al), chromium (Cr), nickel (Ni), selenium (Se), antimony (Sb), manganese (Mn), copper (Cu), arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) were determined by inductively coupled plasma mass spectrometry. The pollution levels of each product and the human health risk resulting from their consumption were then assessed. The concentrations of As in 57 % of samples and Cd in 11 % of samples exceeded the upper limits stipulated by the Chinese National Food Safety Standards (GB 2762-2017), which was mainly due to high concentrations of trace elements in crustaceans and bivalves. The Nemerow integrated pollution index indicated that the aquatic products accumulated high levels of As and Cd. Health risk assessments using the target hazard quotient (THQ) and hazard index (HI) suggested that As and Cd exposure due to consumption of aquatic products presents a potential health risk for residents of Shenzhen.

Recent applications of atomic spectroscopy coupled with magnetic solid‐phase extraction techniques for heavy metal determination in environmental samples: A review

AbstractAtomic spectroscopy is the most popular approach to determine the presence of heavy metals in the environment. Heavy metals are potentially toxic and have various negative effects on many living organisms, including humans. With the rapid increase in the variety of industries and human activities, large amounts of heavy metals are released into the atmosphere, water, and soil. Heavy metal analysis of environmental samples is very important for determining the exposure limits. Environmental samples are highly complex matrices, and various sample preparation techniques have been developed for the extraction of heavy metals from them, including magnetic solid‐phase extraction (MSPE). The use of MSPE in heavy metal analysis has recently gained significant attention owing to a number of advantages. MSPE technique overcomes main issues such as phase separation, handling, and column packing. The use of magnetic adsorbents in sample preparation has grown over the past few years, making MSPE a promising technique for sample preparation. The objective of this review article is to provide the latest applications of MSPE coupled with atomic spectroscopy for heavy metal determination in environmental samples. In addition, new magnetic adsorbents and their analytical merits are emphasized.

Remediation of Heavy Metals in Polluted Water by Immobilized Algae: Current Applications and Future Perspectives

The progression of urban industrialization releases large quantities of heavy metals into water, resulting in the severe heavy metal contamination of the aquatic environment. Traditional methods for removing heavy metals from wastewater generally have varying removal efficiencies, whereas algae adsorption technology is a cost-effective and sustainable bioremediation technique. A green technology that immobilizes algae through a carrier to improve biosorbent’s stability and adsorption performance is immobilization technology. The purpose of this review is to study the optimization strategy of the immobilization of algae for the bioremediation of heavy metals and to comprehensively analyze immobilized algae technology in terms of sustainability. The analysis of the mechanism of heavy metal removal by immobilized algae and the parameters affecting the efficiency of the biosorbent, as well as the approach based on life cycle assessment and economic analysis, allowed the identification of the optimization of the adsorption performance of immobilized algae. This provides a theoretical basis for the practical application of algal bioremediation.

Preparation and characterization of mortar specimens based on municipal solid waste incineration fly ash-activated slag

Municipal solid waste incineration fly ash (MSWIFA) contains a large amount of heavy metals, inhibiting resource utilization. This study used MSWIFA as an alkali activator and ground-granulated blast-furnace slag (GGBS) as a precursor to prepare the MSWIFA GGBS binder. Based on this, used the iron tailing sand instead of natural river sand as fine aggregate prepared mortar specimens by cooperative compression molding. Compressive strength, bulk density, water absorption, and heavy metal leaching tests were conducted and combined with micro XRD, FTIR, and SEM examinations to characterize the mortar specimens. The results show that the optimal MSWIFA: GGBS was 2:8. It was also found that increasing the molding pressure was beneficial to strength development. Compared to the specimens without the application of molding pressure, the 3 d and 28 d strength values increased by 148.6 and 122.2%, respectively, after the application of 35 MPa molding pressure. The reason is that the pressure effect can increase the cohesion of the particles, promote the hydration reaction to proceed, and the hydration products increase to fill the pores, increase the structural compactness and promote strength development. The resource utilization of MSWIFA must be guaranteed not to produce environmental pollution simultaneously. For this reason, the heavy metal leaching test was conducted on 28 d mortar specimens, and the results showed that the leaching rates of Zn, Pb, Cu, Cr, and Ni met the requirements of the Chinese Standard (GB16889-2008). The research results can provide a theoretical basis for the large-scale recycling of MSWIFA.