Mechanisms Of Heavy Metals Research Articles

Natural Enrichment Patterns and Mechanisms of Heavy Metals in Mid-Holocene Soils of the Southern Loess Plateau

Natural Enrichment Patterns and Mechanisms of Heavy Metals in Mid-Holocene Soils of the Southern Loess Plateau

Adsorption behavior and mechanism of heavy metals onto microplastics: A meta-analysis assisted by machine learning

Microplastics (MPs) have the potential to adsorb heavy metals (HMs), resulting in a combined pollution threat in aquatic and terrestrial environments. However, due to the complexity of MP/HM properties and experimental conditions, research on the adsorption of HMs onto MPs often yields inconsistent findings. To address this issue, we conducted a comprehensive meta-analysis assisted with machine learning by analyzing a dataset comprising 3340 records from 134 references. The results indicated that polyamide (PA) (ES = −1.26) exhibited the highest adsorption capacity for commonly studied HMs (such as Pb, Cd, Cu, and Cr), which can be primarily attributed to the presence of C=O and N–H groups. In contrast, polyvinyl chloride (PVC) demonstrated a lower adsorption capacity, but the strongest adsorption strength resulting from the halogen atom on its surface. In terms of HMs, metal cations were more readily adsorbed by MPs compared with metalloids and metal oxyanions, with Pb (ES = −0.78) exhibiting the most significant adsorption. As the pH and temperature increased, the adsorption of HMs initially increased and subsequently decreased. Using a random forest model, we accurately predicted the adsorption capacity of MPs based on MP/HM properties and experimental conditions. The main factors affecting HM adsorption onto MPs were HM and MP concentrations, specific surface area of MP, and pH. Additionally, surface complexation and electrostatic interaction were the predominant mechanisms in the adsorption of Pb and Cd, with surface functional groups being the primary factors affecting the mechanism of MPs. These findings provide a quantitative summary of the interactions between MPs and HMs, contributing to our understanding of the environmental behavior and ecological risks associated with their correlation.

The cementitious properties of alkali-activated municipal solid waste incineration fly ash-phosphorus slag-secondary aluminum dross matrix composites and the mechanism of solidification of heavy metals

Based on the purpose of safe and resourceful disposal of hazardous waste, this paper proposes a new method for the combined treatment of municipal solid waste incineration fly ash (MSWIFA), phosphorus slag (PS), and secondary aluminum dross (SAD). A novel alkali-activated binder was synthesized by orthogonal experimental design, and the strength formation mechanism of the binder and the solidification and stabilization (S/S) mechanism of heavy metals were revealed. The results show that the maximum strength of the sample at 60 d is 22.4 MPa. The addition of SAD will affect the development of the strength of the solidified body and the types of hydration products of the gel. The hydration products of the solidified body are mainly calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and calcium alumina (AFt). The solidified body of alkali-activated cementitious material has a good S/S effect on heavy metals, and its solidification efficiency is Zn > Cd > Pb > Cu > Ni > As > Cr. The maximum solidification rates of Zn, Pb, and Cd were 99.97 %, 97.90 %, and 99.68 %, respectively. At the same time, the leaching concentration of various heavy metals meets the threshold requirements stipulated by relevant international norms and has good environmental safety.

Interaction and selective treatment of lead-zinc flotation wastewater for wastewater recycling using ectrocatalytic internal micro-electrolysis

Lead-zinc flotation wastewater discharge poses a growing risk to environmental safety, and efficient treatment is challenging due to large quantities of water, combined pollution, and the limitations of current approaches. This study discussed the removal differences, available treatment approach, interaction characteristics, and mechanisms of heavy metals (Pb2+ and Zn2+), flotation reagents (butyl xanthate (BX), and dianilino dithiophosphoric acid (DDA)) in single and composite systems using electrocatalytic internal micro-electrolysis (ECIME). Density functional theory (DFT), solubility, and UV spectrum analyses revealed that the high chemical potential of the (BX)2M, (DDA)2M complexes in lead-zinc flotation wastewater played key roles for the solubility and ECIME removal of these pollutants. The complexes significantly inhibited activated carbon (AC) interface adsorption, as well as DDA and (DDA)2M degradation and Fe(II)–Fe(III)–OH flocculation. Prolonging the treatment times for Pb2+, Zn2+, BX, and (BX)2M effectively alleviated the inhibitory effect. However, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) analysis also highlighted the difficulty of the electrochemical reduction deposition of the Pb2+ and Zn2+ reactions. Comparatively, the DDA and (DDA)2M in composite systems showed higher electrochemical stability, while degradation was highly dependent on high voltage and exhibited temporal hysteresis in the ECIME system. The DDA removal rate only reached 60% after ECIME treatment at 45 V for 90 min, while the values of Pb2+ and Zn2+ (9 V, 30 min) and BX (18 V, 70 min) exceeded 90% and exhibited significantly disadvantage effect when voltage was larger than 18 V. Based on the their distinguishing characteristics of ECIME removal and flotation beneficiation effect, an alternative suggested removing of Pb2+, Zn2+ and BX while preserving DDA and (DDA)2Pb in lead-zinc flotation wastewater could be achieved by regulating the reaction potential and time. By adjusting the ECIME settings to a voltage of 15.2 V, a period of 45 min, and a pH of 5.5, a comprehensive removal rate of 97.59% was achieved. Additionally, recycling wastewater at proportions of 50–70% will not lead to confusion in the selection of lead-zinc ore. The results demonstrated the feasibility and economic efficiency of selective removal and reuse, showing considerable potential for practical application.

Heavy Metal Exposure-Induced Cardiovascular Diseases: Molecular Mechanisms and Therapeutic Role of Antioxidants.

Globally, cardiovascular diseases (CVDs) are the main cause of mortality every year worldwide. CVD health is influenced by various health factors, such as blood pressure, cholesterol levels, and glucose control. The main risk factors include smoking, physical activity, food intake, and body mass index. Around 90% of CVDs could be prevented by controlling these risk factors. Heavy metals are indigenous to the environment of the earth. However, modern lifestyles have led to the exploitation of our environment by unconstrained use of heavy metals. Though heavy metals are essential components, they are hazardous to humans and living systems due to their persistent and non-degradable nature. The mainpurpose of this study is to provide a literature review on the mechanisms of heavy metals, particularly arsenic, lead, and cadmium, that cause cardiovascular diseases. The major mechanism by which heavy metals result in various modalities of cardiovascular disease is the generation of reactive species and the depletionof the antioxidant reserves inside the biological system. The generation of reactive species gradually leads to the activation of various signaling pathways, resulting in either apoptosis or unrestricted cell growth. These unfavorable conditions result in a state when there is an imbalance between reactive species generation and antioxidant activity. Both endogenously present antioxidants and dietary antioxidants are very much essential in regulating the redox potential of the body. They help in the detoxification and excretion of heavy metals and their metabolites in the biological system. Therefore, recognizing the role of heavy metals in cardiovascular health is crucial for developing preventive strategies and interventions aimed at mitigating their adverse effects on human health.

Study on the solidification performance and mechanism of heavy metals by sludge/biomass ash ceramsites, biochar and biomass ash.

Industrial by-products are stored in large quantities in the open, leading to wasted resources and environmental pollution, and the natural environment is similarly faced with phosphate depletion and serious water and soil pollution. This study uses these by-products to produce a new sludge/biomass ash ceramsite that will be used to adsorb nitrogen and phosphorus from wastewater, and solidify heavy metals in the soil while releasing Olsen P. The sludge/biomass ash ceramsites are made using sewage sludge and biomass ash in a certain ratio calcined at high temperatures and modified for the adsorption of nitrogen and phosphorus from wastewater. Sludge/biomass ash ceramsites before and after phosphorus adsorption, biochar and biomass ash were compared to analyze their heavy metal adsorption capacity and potential as phosphate fertilizer. After phosphorus adsorption, the sludge/biomass ash ceramsites released effective phosphorus steadily and rapidly in the soil, with a greater initial release than biochar and biomass ash, and the ceramsites were in a granular form that could be easily recycled. Biochar and biomass residue, due to their surface functional groups, are better at solidifying heavy metals than sludge/biomass ash ceramsites. Biochar, biomass ash and sludge/biomass ash ceramsites significantly reduced the concentrations of Cd, Cu, Pb and Zn in the soil. Correlation analysis demonstrated that there was a synergistic relationship between the increase in soil Olsen P content and the change in pH, with the increase in soil Olsen P content and the increase in pH contributing to heavy metal solidification.

Migration and Transformation of Heavy Metal and Its Fate in Intertidal Sediments: A Review

Intertidal sediments are rich in biological resources, which are important for material circulation and energy exchange. Meanwhile, these areas can be treated as sinks as well as sources of coastal heavy metal pollutants. Due to the influence of the tide, the intertidal sediments are in a state of periodic flooding and exposure, and environmental factors such as dissolved oxygen, salinity and overlying water pressure are changeable. Heavy metals in sediments are prone to migration and transformation with the dynamic effects of tidal water and the changes in the environment factors, which increase the bioavailability of heavy metals. In this review, the characteristics of distribution and the bioavailability of heavy metals in intertidal sediments are described; the migration and transformation behavior of heavy metals and its influencing factors under tidal conditions are analyzed; and the mechanisms of heavy metal’s migration and transformation in the intertidal zone are summarized. Moreover, the bioaccumulation of heavy metal by organisms and the remediation techniques are discussed. Therefore, this review systematically summarizes the states of existence, the transport mechanisms, and the fate of heavy metals in the intertidal sediment, fills in the research gap of the cycling of heavy metal in the intertidal zone, and provides a theoretical basis for the control of heavy metal pollution.

The competitive and selective adsorption of heavy metals by struvite in the Pb(II)-Cd(II)-Zn(II) composite system and its environmental significance

The prevalence of struvite and other phosphate minerals in eutrophic environments has a significant effect on the transport and transformation of environmental heavy metals, but their competitive immobilization characteristics and mechanisms for heavy metals remain unclear. Three different sources of struvite (BS, CSHS, and CSS) were obtained respectively by biosynthesis and chemical synthesis with or without humic acid to investigate their competitive immobilization characteristics and mechanism of heavy metals in the Pb(II)-Cd(II)-Zn(II) composite system. The results showed that the immobilization of heavy metals by struvite is physico-chemical adsorption and the affinity (in descending order) is Pb(II) >> Cd(II)/Zn(II). Cd(II) promotes the immobilization of Pb(II)/Zn(II) by BS. The order of the selective strength by struvite for Pb(II) is BS >> CSS ≈ CSHS. The study indicates that the difference between struvite holding heavy metal ions is related to the material composition and heavy metal types, and BS shows best selective immobilization for Pb(II) in the Pb(II)-Cd(II)-Zn(II) composite system. This study provides a theoretical basis for understanding the environmental geochemical role and eco-environmental effects of struvite.

Potential risk, leaching behavior and mechanism of heavy metals from mine tailings under acid rain

The leaching of heavy metals from abandoned mine tailings can pose a severe threat to surrounding areas, especially in the regions influenced by acid rain with high frequency. In this study, the potential risks of heavy metals in the tailings collected from a small-scale abandoned multi-metal mine was assessed, and their leaching behavior and mechanism were investigated by batch, semi-dynamic and in situ leaching experiments under simulated and natural rainfall conditions. The results suggested that Zn, Cu, Pb, and Cd in the tailings could cause high/very high risks. Both batch and semi-dynamic leaching tests consistently confirmed that the leaching of heavy metals (particularly Cd) could lead to serious pollution of the surrounding environment. The leaching rates of heavy metals were pH-dependent and related to their chemical speciations in the mine tailings. The leaching behavior of Cu and Cd was dominated by surface wash-off, Zn was controlled by diffusion initially and then surface wash-off, and the leaching mechanisms of Pb and As varied with the pH conditions. It was estimated that acid rain could greatly elevate the release fluxes of Zn (20.8%), Cu (36.7%), Pb (49.9%) and Cd (35.3%) in the study area. These findings could improve the understanding of the leaching behavior of heavy metals from mine tailings and assist in developing appropriate management strategies.

Effect and mechanism of nano-alumina on early hydration properties and heavy metals solidification/stabilization of alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration (MSWI) fly ash has serious pollution. It needs to be solidification/stabilization (S/S) to sanitary landfill as quickly as possible. In order to achieve the objective, the early hydration properties of alkali-activated MSWI fly ash solidified body were investigated in this paper. Meanwhile, nano-alumina was utilized as an agent to optimize the early performance. Therefore, the mechanical properties, environmental safety, hydration process and mechanisms of heavy metals S/S were explored. The results showed that after adding nano-alumina, the leaching concentration of Pb and Zn in solidified bodies after 3 d curing was significantly reduced by 49.7–63% and 65.8–76.1%, respectively, and the compressive strength was enhanced by 10.2–55.9%. Nano-alumina improved the hydration process, and the predominant hydration products in solidified bodies were C-S-H gels and C-A-S-H gels. Meanwhile, nano-alumina could obviously increase the most stable chemical speciation (residual state) ratio of heavy metals in solidified bodies. Pore structure data showed that, due to the filling effect and pozzolanic effect of nano-alumina, the porosity has been reduced and the ratio of harmless pore structure has been increased. Therefore, it can be concluded that solidified bodies mainly solidify MSWI fly ash by physical adsorption, physical encapsulation and chemical bonding.

Migration, solidification/stabilization mechanism of heavy metal in lightweight ceramisite from co-sintering fly ash and electrolytic manganese residue

Municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue, as hazardous waste, were roasted into lightweight ceramisite with coal fly ash. The migration, transformation and stabilization/solidification mechanism of heavy metals during ceramisite formation process was explored. Heavy metals in ceramisite pellet were concentrated and experienced the transportation among solids below 710 ℃, then heavy metals were prone to flue gas in the form of chlorides above 710 ℃, in particular for Pb, Cd and Cu. Heavy metal chlorides depended on the generation of HCl and Cl2, which needs co-existence of silicon oxide and aluminum oxide. Note that gibbs free energy change of copper chlorides generation reaction decreased with temperature, resulting in higher volatilization rate compared with Mn, Zn and Cr. Remained heavy metals in the solid phase like Cu, Zn and Cr were prone to ion-exchange, balance-charge and specific-adsorb with calcium-bearing minerals (Ca(Mg,Al)(Si,Al)2O6 and (Ca,Fe)SiO3) in ceramisite based on mineral analysis and principle component analysis at 1160 ℃.

Experiment and multiscale molecular simulations on the Cu absorption by biochar-modified asphalt: An insight into removal capability and mechanism of heavy metals from stormwater runoff

Asphalt has been the primary material for pavements and other building components such as roof shingles and waterproofing systems, which can be the path for stormwater runoff pollutants such as heavy metals (HMs). In this study, the capability and mechanism of asphalt and biochar-modified asphalt (BMA) to remove Cu as the typical HM found in the road dust and surface runoff were fundamentally explored for the first time. Experiment and multiscale molecular simulations were performed. Molecular dynamics (MD) simulations showed the Cu absorption into the asphalts. Monte Carlo (MC) and density functional theory (DFT) revealed the detailed mechanism of Cu absorption. Biochar (BC) presence modified the spatial distribution of maltene and asphaltene fractions in asphalt and enhanced the absorption. Maltenes were absorbed into the porous structure of BC, leaving more asphaltenes in the asphalt part of BMA. Asphaltenes were the Cu adsorbing preference sites ascribed to the cation-π interaction between Cu and the aromatic plane. The DFT simulations also suggested favourable adsorption of other commonly found metals (e.g., Cr, Pb, Ni, Cd, and Zn) onto asphaltenes. The present study found the capability and mechanism of BMA and asphalt to remove HMs at the molecular scales, providing a path for designing asphalts with value-added functionality in minimizing environmental pollution.

The control efficiency and mechanism of heavy metals by permeable pavement system in runoff based on enhanced infiltration materials

As one of the commonly used stormwater management measures, permeable pavement system (PPS) played a prominent role in controlling runoff pollution and alleviating urban waterlogging. In this study, new enhanced infiltration materials (construction waste brick, coal gangue, activated carbon, multi-walled carbon nanotube, multi-layer graphene) were applied in PPS and the control efficiency and mechanism of typical heavy metals (HMs, Mn2+, Pb2+, Zn2+, Cu2+, Cd2+, Ni2+) was investigated in runoff. Furthermore, the influences of different rainfall intensities and antecedent dry periods on HMs removal by PPS were evaluated. The results showed that all PPS with enhanced infiltration materials have little leaching effect on HMs (＜3 μg/L). All the selected enhanced infiltration materials meet the requirements of PPS. The concentration of HMs in the effluent of PPS dropped sharply first, followed rebounded and then maintained at a stable range. Activated carbon PPS (AC), Multi-walled carbon nanotube PPS (MCN), and Multi-layer graphene PPS (MG) could significantly improve the control effect of PPS on nearly all selected HMs. The average removal rates of AC, MCN and MG for six HMs were 75.48%–99.35%, 81.30%–97.59%, and 73.03%–99.33%, respectively. Compared with Traditional PPS (TR), the effluent concentrations of HMs in construction waste brick PPS (CW) and coal gangue PPS (CG) were relatively higher and unstable. AC, CN and MG could adapt to different rainfall conditions and the maximum removal rates of most HMs exceed to 99%. With antecedent dry periods increased, the control effect of HMs was significantly improved. The influences of the antecedent drying period on HMs removal followed as: CW＞CG＞TR＞MG＞CN＞AC. This study provided novel methods to eliminating HMs in runoff and provides implications for the design of PPS.

Low-consumption with efficient capture and characteristics of heavy metals from coal combustion by modified kaolin: Experimental and simulation studies

Heavy metals produced by coal combustion tend to bring environmental pollution. The modified additives were prepared by kaolin to capture heavy metals from coal combustion and analyzed by XRD, XRF, FT-IR, SEM and BET. The experimental results showed that the retention rates of heavy metals were ranked as Cr > Zn > Pb > Cd. The best retention of heavy metals was achieved at 1000 °C, while the retention capacity gradually decreased from 1000 to 1300 °C. The trapping effect of heavy metals in dynamic experiment is better than static experiment at 1300 °C. The general ranking of the adsorption capacity of the additives for the four heavy metals was pseudo boehmite-metakaolin (PBK) > aluminum sulfate impregnated metakaolin (AlSK) > metakaolin (MKA) > original kaolin (OKA). The PBK was the best adsorbent with the greatest retention rates of 77.35 %, 74.68 %, 83.35 % and 80.41 % for Pb, Cd, Cr and Zn, respectively. In addition, PBK showed the most significant improvement in the trapping of four heavy metals, with an average improvement of 37.79 % compared to no additives. The geometry models of heavy metal compounds and adsorbents were optimized. The heavy metal oxides were more stable than the chlorides and were more easily adsorbed. There is competitive adsorption between oxides and chlorides of heavy metals. The Al-O-Si-H and Al-O-Si are the best adsorption surfaces for OKA and MKA, respectively. However, CdO and CdCl2 are hardly adsorbed on the Si-O surface of OKA. The frontline orbitals of four heavy metal oxides/chlorides, θ-Al2O3 and α-Al2O3 have been simulated. Computer simulations show that the mechanism of heavy metal oxide/chloride adsorption on additives is a stronger electron transfer induced interaction between the highest occupied molecular orbital of the adsorbate and the lower unoccupied molecular orbital of the adsorbent, which facilitates the formation of stable chemical bonds.

Co-stabilization/solidification of heavy metals in municipal solid waste incineration fly ash and electrolytic manganese residue based on self-bonding characteristics

Municipal solid waste incineration (MSWI) fly ash and electrolytic manganese residue (EMR) were classified as hazardous waste, must be harmlessly processed prior to subsequent treatment or disposal. The competition between massive free manganese ions of raw EMR and other heavy metals was found, thus raw EMR was pretreated by calcining to eliminate competition of manganese with other heavy metals for stabilizer complexation. MSWI fly ash was successfully solidified with 6% NaH2PO4, 6% H2NCSNH2 and 20% sintered EMR (800 °C). The addition of sintered EMR enhanced solidification/stabilization of heavy metals in fly ash and the resulting product had a higher compressive strength for further reutilization like trench backfilling, structural fill and void filling. The stabilization/solidification mechanism of heavy metals was attributed to the combined interaction of heavy metal precipitation in stabilizers and ion exchange or physical encapsulation in silicate compounds like calcium silicate, which is a feasible and valuable approach to co-disposal of MSWI fly ash and EMR.

Solidification/Stabilization of MSWI Fly Ash Using a Novel Metallurgical Slag-Based Cementitious Material

Four industrial wastes, i.e., blast furnace slag, steel slag, desulfurization ash, and phosphoric acid sludge, were used to prepare a low-carbon binder, metallurgical slag-based cementitious material (MSCM). The feasibility of solidification/stabilization of municipal solid waste incineration (MSWI) fly ashes by MSCM were evaluated, and the immobilization mechanisms of heavy metals were proposed. The MSCM paste achieved 28-day strength of 35.2 MPa, showing its high-hydration reactivity. While the fly ash content was as high as 80 wt.%, the 28-day strength of MSCM-fly ash blocks reached 2.2 MPa, and the leaching concentrations of Pb, Zn, Cr, and Hg were much lower than the limit values of the Chinese landfill standard (GB 16889-2008). The immobilization rates of each heavy metal reached 98.75–99.99%, while four kinds of MSWI fly ashes were solidified by MSWI at fly ash content of 60 wt.%. The 28-day strength of binder-fly ash blocks had an increase of 104.92–127.96% by using MSCM to replace ordinary Portland cement (OPC). Correspondingly, the lower leachability of heavy metals was achieved by using MSCM compared to OPC. The mechanisms of solidification/stabilization treatment of MSWI fly ash by MSCM were investigated by XRD, SEM, and TG-DSC. Numerous hydrates, such as calcium silicate hydrate (C-S-H), ettringite (AFt), and Friedel’s salt, were observed in hardened MSCM-fly ash pastes. Heavy metals from both MSWI fly ash and MSCM could be effectively immobilized via adsorption, cation exchange, precipitation, and physical encapsulation.

Insight into different removal behaviors and mechanism of heavy metals via sulfate-loaded layered double oxide

Sulfur-containing materials with high affinity toward heavy metals have recently aroused great research enthusiasm. Yet the removal differences and mechanisms for various heavy metals remain unclear in view of rarely systematical reports. In this regard, a sulfate-loaded adsorbent (MgAl-LDO@S) synthesized by precursor-calcination strategy was employed for investigating the removal differences of heavy metals (i.e., Pb(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ), typical heavy metals in wastewater). As predicted, a diverse adsorption capability for metals on MgAl-LDO@S was observed, following the order of Pb(Ⅱ) (631.90 mg g−1) > Cd(Ⅱ) (208.27 mg g−1) > Ni(Ⅱ) (119.02 mg g−1). Both adsorption isotherm and kinetic demonstrated that the monolayer, heterogeneous-homogeneous, and multilayer adsorption occurred in Pb(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ), respectively, which were controlled by chemisorption. Furthermore, the removal differences were deeply exploded via the combination of XRD, FT-IR and XPS analyses and contribution calculation. The ion exchange was the main adsorption mechanisms for Pb (II) with 44.77%, while complexation dominated in Cd(II) and Ni(II) removal, with the proportion of 53.36% and 55.89%, respectively. Besides, the solubility constant (Ksp) of precipitate, affinity of sulfate group, as well as the self-characteristic properties contributed to various removal ability for heavy metal ions (e.g., ionic radius, electronegativity, and hard-soft-acid-base attribute) as well.

Co-pyrolysis of industrial sludge and rice straw: Synergistic effects of biomass on reaction characteristics, biochar properties and heavy metals solidification

Co-pyrolysis of sludge and biomass was conducted to produce biochar with heavy metals solidification. The synergistic coupling mechanism and the surface functional groups and pore structure characteristics of co-pyrolytic biochar were studied. The solidification characteristics and mechanism of heavy metals were also investigated. Biomass composition in the co-pyrolysis system provided energy, solidified heavy metals and improved product quality. Compared with the weighted calculated value of two individual materials, the secondary decomposition process of co-pyrolysis was prolonged by approximately 80 °C and enhanced by 29%. OH bond, CH bond, and CO bond of co-pyrolytic biochar obtained at 500 °C increased significantly, and the carbon network structure and skeleton were enhanced, and the specific surface area increased by 102.8%, comparing with that of sludge biochar. The solidification effect of Cu and Cd in co-pyrolytic biochar was 29% and 50% higher than that in sludge biochar, respectively. The leaching rates of Cu and Cd in co-pyrolytic biochar were only 38.22% and 39.54% of that from sludge biochar. This study demonstrated that high-quality biochar with low heavy metal risk can be obtained by co-pyrolysis technology, which provides a potential way for the comprehensive utilization of industrial sludge and biomass.

Lead-Zinc Tailings-Based Construction Mortars/ Preparation, Performance and Stabilization Mechanism of Heavy Metals

Lead-Zinc Tailings-Based Construction Mortars/ Preparation, Performance and Stabilization Mechanism of Heavy Metals

Mechanisms of heavy metal and oil removal from synthetic saline oilfield produced water by electrocoagulation

In the present study, an electrocoagulation process was applied to treat saline oilfield-produced water. The kinetics of simultaneous heavy metal and oil removal in the saline environment under different conditions including four-electrode materials of copper, zinc, iron, and aluminum, aeration and agitation rate, oil content, and salinity was investigated. The nature of the electro-generated species and possible abatement mechanisms were explored and compared by using FE-SEM/EDS, FTIR, XRD, and BET analyses. At low and high salinities, cadmium adsorption followed Langmuir and Freundlich models, suggesting the transformation of identical adsorption sites to heterogeneous ones. Cadmium removal efficiencies of 99/73% were obtained at low/high salinity with iron and 99.9 and 82% using copper and zinc electrodes in a saline environment. The cadmium adsorption capacity of different anode materials exhibited the order of copper > zinc > iron > aluminum. The adsorption capacity was considerably reduced in saline condition due to more crystalline structure and lower surface area and porosity of the particles while it was enhanced by the oil, caused by structural changes including more uniform pores, the elevated surface area, and porosity. The COD removal yield of 89% for low salinity and 80/73% at high salinity with/without aeration were achieved by iron. The highest COD removal yield of about 95% was achieved by the aluminum electrodes, compared to 85 and 87% for copper and zinc electrodes. The main removal mechanisms were outer- and inner-sphere complexation, and surface precipitation.