Leaching Of Pb Research Articles

A method of pretreating incineration ashes containing metallic aluminium using NaOH to mitigate volume expansion under highly alkaline conditions

Globally, millions of tonnes of incineration ashes are produced with a substantial portion remaining underutilized in low-value applications or disposed in landfills. Many types of fly ashes and bottom ashes contain metallic aluminium (Al0), which causes volume expansion when the ashes are used in alkali-activated materials and as a supplementary cementitious material due to the generation of hydrogen gas at high-pH conditions. This phenomenon significantly restricts the potential applications of these ashes. To address this issue, ashes can be pretreated with NaOH to oxidize the metallic aluminium (Al0) before their utilization. This study focuses on investigating the effect of the NaOH pre-treatment duration on fly ashes from the co-combustion of recovered solid fuel, peat, and wood. A pre-treatment process was conducted using 8 mol/L aqueous NaOH solution to treat the fly ash for up to 60 minutes. The formed slurry was subsequently used to prepare alkali-activated material by mixing it with bottom ash and employing either sodium silicate or sodium carbonate as an alkali activator. The NaOH pre-treatment demonstrated a 100 % metallic aluminium conversion into oxidized form resulting enhancement in mechanical performance, microstructure, and water absorption properties. The proposed method offers a highly efficient and rapid solution for eliminating the drawbacks caused by the presence of metallic aluminium and it can be conveniently implemented on construction sites. Concurrently, this study also explores the leaching behaviour of heavy metals during alkali-activation. Significant reductions in the leaching of Ba, Cr, Cu, Mo, and Pb were observed, highlighting the environmental remediation potential of alkali-activation methods.

High-temperature anaerobic calcination for stabilizing environmentally stressful elements in phosphoric acid production by-products

Phosphorus tailings (P) refer to the waste materials left over after the extraction of phosphorus from phosphate rock during mining and processing. phosphogypsum (PG) is typical by-products of phosphoric acid production (PPB), containing numerous environmentally hazardous elements (EHE) that pose significant risks to ecological safety. In this study, we examined the impact of high-temperature anaerobic calcination on the migration and immobilization of EHE in PPB. The results indicated that higher temperature ranges favorably controlled the leaching toxicity of PPB. In the calcination products of P and PG, the inhibition efficiency of Pb leaching toxicity reached 84.93% and 89.33%, respectively. Under higher temperature conditions (P at 700 °C, PG at 600 °C), the inhibition of Cr leaching toxicity reached 100%. The inhibitory effects of high-temperature environments on EHE in PPB were ranked as fluorine > phosphorus > heavy metals. The mechanisms of migration and transformation of EHE in PPB under high-temperature anaerobic calcination were elucidated in three aspects, ranked from strongest to weakest. Firstly, the encapsulation of EHE by a shell-like structure, attributed to the “melt-wrap” phenomenon. Secondly, the decomposition-gasification phenomenon induced by high-temperature conditions. Thirdly, the effect of high temperature on the transformation of the storage forms of EHE. This study fills a research gap in the field of thermal treatment of PPB, enhancing the understanding of the specific effects of thermal treatment on the transformation of EHE in PPB, and provides theoretical and data support for the high-temperature thermal treatment of solid wastes.

Comparison of Pb adsorption and transformation behavior induced by chicken manure and its DOM in contaminated soil

Organic fertilizer derived from animal manure can significantly improve soil fertility. However, limited research has investigated the capacity of exogenous organic fertilizer dissolved organic matter (DOM) to migration and transform heavy metals. In this study, the effect of chicken manure organic fertilizers with different maturity and their DOM on changes of Pb bioactivity was evaluated and the role of soil environmental factors driving the changes was determined through soil incubation, adsorption and leaching experiments. The FTIR results indicated that DOM derived from farmhouse chicken manure organic fertilizer (FCMD) contained more protein-like compounds and low maturity, while DOM from commercial chicken manure organic fertilizer (CCMD) contained more humic/fulvic acid and high maturity. FCMD and CCMD reduced the content of RES-Pb by 16.3–27.52 % and 6.66–13.98 %, respectively. And the effects of organic fertilizers and their DOM on Pb migration and activation follow the order of FCMD> CCMD> CK> commercial chicken manure organic fertilizer (CCM)> farmhouse chicken manure organic fertilizer (FCM). FTIR analysis showed that FCMD was primarily composed of aromatic unsaturated functional groups, and its adsorption capacity for Pb2+ was significantly lower than that of FCM. In addition, the application of FCMD significantly altered the physicochemical properties of soil and promoted the migration and leaching of Pb. FCMD not only causes the soil Pb2+ to be released into the effluent but also activates Pb from the stable form into the active form. In summary, animal manure with lower maturity has a risk to activate heavy metals and should be applied with cautions.

Dynamic leaching behaviors of heavy metals from recycled coal gangue aggregate under loading conditions during solid backfill mining

In solid backfill coal mining, recycled coal gangue aggregate (RCGA) is subject to the combined effects of overlying strata stress and leaching by mine water in the goaf. This process causes heavy metals to be leached and released from RCGA, which can lead to groundwater contamination. In this study, the release patterns of heavy metals in RCGA under the coupled effects of stress, solution pH, and solution flow rate were investigated, and the interactions between RCGA and the surrounding environment were explored. The findings indicate that: (1) The combined action of effective stress and mine water promotes the leaching of heavy metals. Specifically, the leaching of Pb, Zn, and Mn of RCGA is primarily influenced by the pH value of the leaching solution, while the leaching of Cu and Cr of RCGA is more closely related to the stress level; (2) Acidic environments accelerate the release of carbonate-bound fraction (CAR) in elements, facilitating the transformation of Fe/Mn oxide-bound fraction (XXI) into soluble forms; (3) The leaching ratios (Lr) of heavy metals follow the order: LrZn > LrPb > LrMn > LrCu > LrCr. This research provides guidance for the safe application of RCGA in solid backfill coal mining.

Efficient removal and recovery of lead from high arsenic antimony oxide powder

The existence of Pb in crude antimony oxide powder(CAOP) hinders the further smelting and recovery of Sb and leads to some environmental problems. Therefore, the selective removal of Pb from CAOP is important for the production of high-purity antimony products. In this work, Pb in CAOP is removed by HNO3 leaching, achieving purification of CAOP. Then H2SO4 is used to recover Pb from the HNO3 leaching solution. The Pb leaching efficiency reaches 98.9 %, resulting in a decrease in the Pb content from 4.56 % to 0.20 % in CAOP. The Sb leaching efficiency is controlled at around 5.0 %. These confirm HNO3 has good selectivity. The HNO3 disrupts the molecular structure of the raw materials during the leaching, resulting in the conversion of Sb2O3 and As2O3 into insoluble AsSbO4. By adding H2SO4 to the leaching solution, the Pb precipitation efficiency reaches 93.6 %. After Pb removal, the leaching solution can be re-used for the leaching of Pb, while the residue can be directly returned to the pyrometallurgical system. The reaction mechanism and a novel approach for removing Pb from CAOP are proposed, which have the advantages of high selectivity, effective Pb separation, and recoverable HNO3.

Prediction of the fluoride contents of different crop species via the random forest algorithm.

Fluoride (F) is a trace element that is essential to the human body and occurs naturally in the environment. However, a deficiency or excess of F in the environment can potentially lead to human health issues. The pseudototal amount of F in soil often does not correlate directly with the F content in plants. Instead, the F content within plants tends to have a greater correlation with the bioavailable F in soils. In large-scale soil surveys, only the pseudototal elemental content of soils is typically measured, which may not be highly reliable for developing agricultural zoning plans. There are significant variations in the ability of different plants to accumulate F from soil. Additionally, due to variations in soil elemental absorption mechanisms among different plant species, when multiple crops are grown in an area, it is typically necessary to study the elemental absorption mechanisms of each crop. To address these issues, in this study, we examined the factors influencing F bioaccumulation coefficients in different crops based on 1:50,000 soil geochemical survey data. Using the random forest algorithm, four indicators-bioavailable P, bioavailable Zn, leachable Pb, and Sr-were selected from among 29 parameters to predict the F content within crops to replace bioavailable F in the soil. Compared with the multivariate linear regression (MLR) model, the random forest (RF) model provided more accurate and reliable predictions of the fluoride content in crops, with the RF model's prediction accuracy improving by approximately 95.23%. Additionally, while the partial least squares regression (PLSR) model also offered improved accuracy over MLR, the RF model still outperformed PLSR in terms of prediction accuracy and robustness. Additionally, it maximized the utilization of existing geochemical survey data, enabling cross-species studies for the first time and avoiding redundant evaluations of different types of agricultural products in the same region. In this investigation, we selected the Xining-Ledu region of Qinghai Province, China, as the study area and employed a random forest model to predict the crop F content in soils, providing a new methodological framework for crop production that effectively enhances agricultural quality and efficiency.

Stabilization of Pb/Zn mine tailings by modified fly ash: characterization, performance, and mechanism.

The presence of heavy metals in mine tailings poses a serious threat to the surrounding environment. In this study, we aimed to stabilize Pb/Zn-containing mine tailings using modified fly ash (FA) with various alkali solutions. Notably, the modification of FA with Na2SiO3 (NaSi-FA) resulted in the most significant structure changes. To understand the adsorption mechanism of Pb and Zn by modified FA, batch adsorption experiments were conducted. Doubling the adsorption capacity for both Pb and Zn was observed in the modified FA samples compared to unmodified samples. These results could be attributed to the enhanced surface area and porous structure, providing more anchor sites for the heavy metal ions. Additionally, the adsorption of Pb and Zn was found to follow the Langmuir isotherm and pseudo-second order kinetic. Molecular dynamics simulations further supported the notion that Pb and Zn ions could effectively exchange with Na ions within the N-A-S-H gel network, ultimately solidifying them in its structure. Stabilizing Pb/Zn tailings with NaSi-FA resulted in a significant decrease in the leaching of Pb and Zn. Specifically, the leading amount decreased by 55.2% for Pb and 35.3% for Zn, showcasing the superior performance of this stabilization method. This reduction in leaching indicates effective compliance with environmental regulations regarding the containment of Pb and Zn.

The potential of phosphate mine tailings in the remediation of acidic Pb-contaminated soil

We investigated the potential of tailings from phosphate mining, consisting of phlogopite, carbonate minerals calcite and dolomite, and residues of apatite, to serve as a stabilizing agent in the remediation of Pb-contaminated soil in situ or on-site. In a 2.5-year field trial, test plots located in a former shooting range area were surface-treated with the tailings and analyzed for tailings-induced changes in Pb solubility and thus potential mobility within the soil profile. The factors and mechanisms controlling tailings-induced changes in Pb solubility in various soil types, and the susceptibility of Pb to leaching down the soil profile following the treatment, were investigated in supplementary laboratory-scale experiments carried out with horizon-specific soil samples collected from the field site. In the tailings-treated soil, the dissolution of the carbonate fraction of the tailings and the subsequent increase in soil pH contributed to the displacement of shot-derived Pb2+ ions by the carbonate-derived calcium ions (Ca2+) and the adsorption of Pb2+ by soil organic matter and Al, Fe, and Mn (hydr)oxide surfaces. Moreover, the apatite fraction of the tailings formed poorly-soluble compounds with Pb, particularly in soils high in exchangeable Pb2+ with respect to their cation exchange capacity. Consequently, the Pb solubility in tailings-treated soils substantially decreased. The reduction in Pb solubility was most evident in the organic topsoil high in Pb. Despite the liming effect of the tailings, and the susceptibility of Pb to form organic complexes conducive to solubilization upon an increase in pH, we found no evidence of tailings-induced leaching of Pb down the soil profile.

Leaching behavior of Cu, Zn, Fe and Pb from polymetallic tailings

ABSTRACT Copper tailings are a common byproduct of copper production, containing high levels of heavy metals which are released into the environment. Conventional methods have historically prioritized copper recovery, and often overlooking the leaching of other valuable elements. However, the rising demand for nonferrous metals necessitates understanding their leaching behavior from copper tailings. This study examined the atmospheric leaching of Cu, Fe, Pb, Zn, and CuO from a polymetallic tailing ore. Leaching recoveries of 63.5% for Cu, 97.5% for CuO, 1% for Fe, and 100% for Zn were achieved under the optimum conditions of 0.5 M sulfuric acid concentration, 25% solids percentage, 65°C, stirring speed of 100rpm, particle size of 75 µm within 30 minutes. Results indicated that the dissolution of oxide minerals such as CuO and ZnO was significant; however, copper sulfides need oxidant to be dissolved. In this condition, iron oxides and silicates were partially reacted by sulfuric acid, and Pb-bearing minerals formed lead sulfate. The presence of iron and lead-bearing minerals in the leaching residue was confirmed by XRF, XRD, and SEM analyses, and was in agreement with the information displayed in the Eh-pH diagrams.

Fractionation and leaching of Cd, Cu, Fe, Pb, and Zn from smelter residues of an old environmental liability in Argentina

An integrated chemical and mineralogical characterization approach was applied to smelter wastes collected from 50-year-old dump sites in Argentina. Characterization included pseudo-total element concentrations, acid generation/neutralization potential, sequential extractions, pH-dependent leaching kinetics, and mineralogical analysis of all residues. These analyses provided detailed information on the reactivity of the minerals in the waste material and associated metal release. Cadmium and Zn were the elements of greatest environmental concern due to their high mobility. On average, the release of Zn and Cd in pH-dependent leaching essays reached 17.6% (up to 5.24 mg g−1) and 52.7% (up to 0.02 mg g−1) of the pseudo-total content, respectively. Moreover, Cd and Zn were also the metals that showed the higher proportions of labile fractions associated to the adsorbed and exchangeable fraction (60–92% for Cd and 19–38% for Zn). Since Cd and Zn concentrations in the residue are not high enough to form their own minerals, a large proportion of these elements would be weakly adsorbed on Fe oxyhydroxides. In contrast, the low release of Cu, Pb and Fe would be associated with these elements being incorporated into the crystalline structure of insoluble or very poorly soluble minerals. Lead is incorporated into plumbojarosite and anglesite. Copper was mainly in association with Fe oxyhydroxides and may also have been incorporated into the plumbojarosite structure. The latter could act as a sink especially for Pb under the acidic conditions of the smelter residue. Despite the elevated concentrations of Pb observed in the residue, it showed a very low mobility (≈0.1%), indicating that it is mostly stabilized. Nevertheless, the smelter residue is a continuous source of metals requiring remediation.

Ladle slag–based binder for the solidification/stabilization of heavy-metal-rich industrial waste

Heavy metal pollution from industrial sources is a major environmental and health hazard on a global scale. This study introduces a solidification/stabilization method of industrial waste using a waste-based, ettringite-rich solid binder from ladle slag and gypsum for the immobilization of an industrial waste material with extremely high contents of several heavy metals. The importance of sulfate and water content on the immobilization efficiency and the use of citric acid to increase the processing time of the binder were studied. The leaching of Pb, Hg, Se, As, Cd, Cu, and Ni was measured, and X-ray powder diffraction, field-emission scanning electron microscopy, and field-emission electron probe microanalysis combined with wavelength-dispersive X-ray spectroscopy were used to analyze the structure of the hardened binder and the location of the heavy metals within. The study shows that the ladle slag/gypsum binder is suitable for the solidification/stabilization of heavy-metal-rich solid industrial waste. Hg, As, Cd, Cu, and Ni were fully immobilized in all scenarios covered in the study, whereas Pb and Se showed more complicated behaviors. The main immobilization method was encapsulation, and partial Se incorporation into ettringite was observed. The presence of citric acid increased the processing time of the binder without harming the immobilization, unless combined with low sulfate content.

Towards Safe Diatomite Sludge Management: Lead Immobilisation via Geopolymerisation

Diatomite, a natural adsorbent rich in active silica, serves as a valuable precursor for geopolymer synthesis. The safe disposal of diatomite as a failed lead (Pb(II)) adsorbent is critical to prevent secondary contamination. This study investigated the immobilisation efficiency of geopolymerisation for Pb(II)-rich diatomite sludge. Low-grade diatomite with high ignition loss was utilised in the synthesis of alkali-activated geopolymers. It was demonstrated that the geopolymers achieved a compressive strength of 28.3 MPa with a 50% replacement rate of metakaolin by diatomite sludge, which was not a compromise in strength compared to that of the geopolymer with no Pb(II) (26.2 MPa). The leaching behaviour of Pb(II) was evaluated using water and acetic acid, yielding concentrations below 3 mg/L and immobilisation efficiencies of 95% in both scenarios. Analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) elucidated the mineral composition and chemical environment of the geopolymers. These analyses revealed that Pb(II) migrated from diatomite pores, potentially forming soluble hydroxides under sufficient hydroxide, which then participated in condensation with silicon and aluminium monomers, effectively immobilising Pb(II) within amorphous aluminosilicate gels. Furthermore, the formation of the amorphous gels within diatomite pores hindered Pb(II) leaching, encapsulating Pb(II) effectively. This study presents a novel approach to immobilising heavy metals within building materials, enhancing mineral resource utilisation efficiency while addressing environmental contamination concerns.

Stabilization of lead (Pb)- and arsenic (As)-contaminated soil using pen shells (Atrina pectinata).

Pen shells (PS), a type of shellfish, are abundantly consumed, and their inedible shell residues are often discarded near the coast without consideration of reutilization. This study sought to investigate the use of natural pen shells (NPS) and calcined pen shells (CPS) to stabilize Pb and As-contaminated soil. During the investigation, NPS and CPS were applied to the contaminated soil in amounts ranging from 1 to 10 wt% and cured for 28days. After the curing process, the mineral phase was examined through X-ray powder diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analysis. The XRD and SEM-EDX results revealed the presence of riversideite and ettringite, which contribute to Pb and As stabilization in the CPS-treated soil. The leachability of Pb and As in the treated soil was further examined with three types of chemical extraction methods. Extraction results using 0.1M HCl displayed a notable pH fluctuation in the extractant due to the residual amendments (NPS and CPS). The fluctuation resulted in a strong correlation of leached Pb and As with the pH of the extractant, which might hinder an accurate assessment of stabilization. In order to minimize the effect of pH, an EDTA-NH4OAc extraction was employed, suggesting its potential as a suitable assessment method. EDTA-NH4OAc extraction showed a higher effectiveness of CPS than NPS at 10 wt% of input amounts. In the SBET extraction, that uses a strongly acidic solution, a higher As leachability was observed by increasing the addition of CPS, which implied a CPS-related chemical fixation mechanism. The comparison of various extraction methods showed a higher CPS effectiveness as compared to NPS. However, it was recommended that CPS-treated soil required caution in strongly acidic conditions, especially for arsenic. This study explores the applicability of PS, which has not been investigated as an amendment for Pb and As-contaminated soil previously. Furthermore, this study revealed that utilization of various extraction methods is beneficial for gaining a comprehensive understanding of the role of CaCO3-based amendment in Pb and As-contaminated soil.

Functionality of wheat straw-derived biochar enhanced its efficiency for actively capping Cd and Pb in contaminated water and soil matrices: Insights through batch adsorption and flow-through experiments

The impact of functionality of biochar on pressing environmental issue of cadmium (Cd) and lead (Pb) co-contamination in simultaneous soil and water systems has not sufficiently reported. This study investigated the impact of Fe- and Mg-functionalized wheat straw biochar (Fe-WSBC and Mg-WSBC) on Cd and Pb adsorption/immobilization through batch sorption and column leaching trials. Importantly, Fe-WSBC was more effective in adsorbing Cd and Pb (82.84 and 111.24 mg g−1), regeneration ability (removal efficiency 94.32 and 92.365), and competitive ability under competing cations (83.15 and 84.36%) compared to other materials (WSBC and Mg-WSBC). The practical feasibility of Fe-WSBC for spiked river water verified the 92.57% removal of Cd and 85.73% for Pb in 50 mg L−1 and 100 mg L−1 contamination, respectively. Besides, the leaching of Cd and Pb with Fe-WSBC under flow-through conditions was lowered to (0.326 and 17.62 mg L−1), respectively as compared to control (CK) (0.836 and 40.40 mg L−1). In short, this study presents the applicable approach for simultaneous remediation of contaminated water and soil matrices, offering insights into environmentally friendly green remediation strategies for heavy metals co-contaminated matrices.

Deteksi Konsentrasi Fe, Cu, Zn dan Pb Air Sungai dan Ikan yang Tercemar Air Lindi di Bandar Lampung Dengan Menggunakan SSA

Leachate is a pollutant produced by landfills which can pollute the aquatic environment. This will have an impact on fish that live in waters contaminated with leachate and if consumed by the public it will harm health. The toxic effects of leachate are caused by the content of toxic chemicals, one of which is heavy metals. The aim of this research was to determine the concentrations of Fe, Cu, Zn and Pb in Bakung landfill leachate, Sukamaju river water and fish meat. Bakung landfill leachate samples were taken from two outlet points. The fish sampling location was carried out in the Sukamaju River. The physical factors of water measured are temperature, pH, salinity, turbidity, DO, COD and BOD. Fe, Cu, Zn and Pb concentrations were measured using the Atomic Absorption Spectrophotometry (AAS) method. The results show that the physicochemical parameters in leachate and river water exceed the threshold. The contents of Zn, Cu, Fe and Pb in the leachate at both outlet points exceeded the threshold value with values of 2.48 mg/L and 2.80 mg/L; 16.55 mg/L and 17 mg/L; 0.078 mg/L and 0.113 mg/L; 3.26 mg/L and 3.01 mg/L. The concentration of heavy metals Pb and Fe in river water is 0.083-0.162 mg/L and 2.68-2.97 mg/L which are above the quality standard value, while the heavy metal Fe content in fish meat exceeds the specified threshold value, namely 0.557 mg/100 g and 0.564 mg/100 g.

Fate of Ca2+ and metal impurities of a typical coal fly ash in amino acid mediated CO2 mineralization and simultaneous CaCO3 recovery

CO2 mineralization is a promising technology to achieve a waste-to-resource chain by integrating CO2 sequestration and alkaline solid waste utilization. Amino acids as a multifunctional reagent was proposed to avoid the extensive consumption of acid and alkaline reagents in traditional processes. However, the detailed interaction between Ca-bearing minerals and amino acids are still not fully understood, as well as migration pathways of metal impurities. To fill these gaps, this paper investigated the leaching and carbonation behaviors of Ca2+ and metal impurities of a typical coal fly ash (CFA) at various reagent types, reagent concentrations and leaching temperatures, thereby exploring the fate of these metal impurities. Results showed that the leaching and carbonation of Ca2+ was influenced by various aspects such as initial pH, reagent pKa, complexation, and pH buffering. The CaCO3 products obtained from glycine (Gly) and alanine (Ala) were vaterite due to the stabilizing effect of these amino acids on vaterite preventing it from converting to calcite. The optimal reaction conditions were 1.0 M Gly and leaching temperature of 35 °C with 26.63 % leaching efficiency, 56.08 % carbonation efficiency, and 42.6 g/kg vaterite yield. In addition, Ala induced an unexpected high leaching efficiency of Cd (75.79 %), Pb (76.08 %), and Zn (41.62 %), respectively, indicating promising mitigation of the environment risk of leached residue and valuable metal recovery from CFA. Although Gly displayed limited metal leaching efficiency at 1.0 M and 25 °C, increasing leaching temperature induced a remarkable enhancement of Cd and Pb leaching, which were 88.54 % and near 100 % at 35 °C, indicating promising mitigation of the environment risk of leached CFA. However, the high binding affinity of amino acids to impurity metals led to the low purity of CaCO3 product. This study derives the migration pathways of various metal ions during the mineralization and utilization of CFA, making it of great significance for the resource management and utilization of solid wastes.

Improving the stabilization/solidification performance of Pb-containing alkali-activated slag via incorporation of superabsorbent polymer

Alkali-activated materials (AAM) have garnered significant attention for the treatment of Pb-contaminated solid waste, attributed to their low carbon footprint and superior stabilization/solidification (S/S) capabilities. However, recent concerns arise regarding their long-term S/S performance, especially when exposed to rainwater environments and considering the inherent shrinkage and potential cracking of AAM. This research delves into the feasibility of enhancing the S/S efficacy of alkali-activated slag (AAS) through the integration of super absorbent polymers (SAP). Findings reveal a marked improvement in the S/S performance of Pb-laden AAS upon SAP addition. Specifically, incorporating 0.5 wt% and 1 wt% SAP curtailed Pb leaching in AAS samples (cured for 90 days) by 47 % and 75 %, respectively. Comprehensive analyses using XRD, TGA, MIP, BSEM, EDX, XPS and MAS NMR suggest that the bolstered S/S performance of SAP-augmented AAS is not rooted in alterations to the reaction degree, pore structure, or reaction products of AAS. Instead, it hinges on the innate capacity of SAP to absorb and retain Pb. Leaching tests reveal that, in AAS cured for 90 days, approximately 1.72 mg of Pb ions were retained per gram of SAP. This investigation furnishes a novel vantage point for refining and deploying alkali-activated materials (or other cementitious materials) as effective S/S agents.

Comparison of Phosphogypsum-Steel Slag-Based cement and Portland cement for stabilization of heavy metals in oil-based drillings cuttings

This research compared Portland cement and Phosphogypsum-Steel Slag-Based (PSSB) cement in terms of their capabilities to stabilize heavy metals (specifically lead and nickel) in Oil-Based Drill Cuttings (OBDC). In the experimental section, the qualitative analysis of heavy metal constituents in OBDC was captured by X-ray Photoelectron Spectroscopy (XPS). Additionally, an acetic acid leaching test was implemented for the heavy metal leaching concentration to evaluate the ceramsite stabilization effect on OBDC. In the simulation phase, cement models, heavy metal ion models, and stabilization models were constructed to explore the stabilization mechanism of heavy metals. Results demonstrated that PSSB cement exhibits superior stabilization effects on OBDC compared to Portland cement. Flame Atomic Absorption Spectrophotometry (FAAS) tests showed that PSSB cement reduced Ni and Pb leaching by 21.87 % and 47.32 %, respectively, compared to Portland cement. In PSSB cement, the diffusion coefficients for Ni and Pb ions were observed to decrease by 42.92 % and 79.63 %, respectively, as revealed through Mean Square Displacement (MSD) analysis. The cohesive energy of PSSB cement was 76.73 % lower than that of Portland cement, and its interaction energies for stabilizing Ni and Pb ions were 59.43 % and 76.22 % lower, respectively, demonstrating greater stability and efficiency in metal stabilization. PSSB cement exhibited lower heavy metal concentration and better structural stability than Portland cement.

Novel piezoelectric xNF–(1−x)PZT materials for catalytic/photocatalytic removal of pollutants

This study explores the potential of using nanocomposite powders consisting of NiFe2O4 and Pb(Zr0.47Ti0.53)O3 in varying concentrations (30 %, 40 %, 50 %, and 70 wt.%) to remove pollutants from water-based solutions. XRD, FTIR, and XPS analyses showed the successful synthesis of the pure ferrite phase directly on the ferroelectric templates. The presence of all elements specific to parents NF and PZT can be observed by XPS and EDS analyses. The AFM and PFM observations suggest that the addition of NF can locally enhance and possibly improve the piezoelectric properties. The degradation efficiency was tested under different conditions (mechanical stirring, ultrasonic vibration, and UV irradiation). The results showed that the nanocomposites exhibited high efficiency in the degradation of the reactive yellow 84 dye and Bisphenol A, with an optimum composition of x = 40 % NiFe2O4 addition, in line with PL tests. Also, no leached Pb ions could be detected in the solution. Furthermore, a simple rotational stirring method was found to be a fast and effective way to degrade the micropollutants.

Roles of the SOM and clay minerals in alleviating the leaching of Pb, Zn, and Cd from the Pb/Zn smelter soil: Multi-surface model and DFT study

Soil organic matter (SOM) and clay minerals are important sinks for reactive heavy metals (HMs) and exogenous hydrogen ions (H+). Therefore, HMs are likely to be released into soil porewater under acid rainfall conditions due to the competitive adsorption of H+. However, negligible Lead, Zinc, and Cadmium (<6 ‰) in the Pb/Zn smelter soil were leached, and the effects of SOM and clay minerals on HMs leaching were unclear. Herein, the H+ consumption and HMs redistribution on SOM and clay minerals were quantitated by the multi-surface model and density functional theory calculations to reveal the roles of SOM and clay minerals in alleviating HMs' leaching. Clay minerals consumed 43.2 %–52.0 % of the exogenous H+, serving as the dominant sink for the exogenous H+ due to its high content and hindering H+ competitive adsorption on SOM. Protonation of the functional groups constituted >90 % of the total H+ captured by clay minerals. Meanwhile, some H+ also competed with HMs for adsorption sites on clay minerals due to its 0.497-fold to 1.54-fold higher binding energies than HMs, resulting in the release of HMs. On the contrary, SOM served as an accommodator for taking over the released HMs from clay minerals. The HMs complexation on the low-affinity sites (R-L−) of SOM was responsible for the recapture of HMs. In Ca-enriched soil, the released HMs were also recaptured by SOM via ion exchange on the R-L-Ca+ and the high-affinity sites (R-H-Ca+) sites due to the 30.8 %–178 % higher binding energies of HMs on these sites than those of Ca. As a result, >63.4 % of the released HMs from clay minerals were transferred to the SOM. Thus, the synergy of SOM and clay minerals in alleviating the leaching of HMs in Pb/Zn smelter soils cannot be ignored in risk assessment and soil remediation.