Stabilization Of Heavy Metals Research Articles

Multifaceted Impact of Lipid Extraction on the Characteristics of Polymer-Based Sewage Sludge towards Sustainable Sludge Management

Dewatered sludge (DS) is a sewage sludge with a unique property due to extracellular polymeric substances (EPSs) and polymer flocculants. These components form a stable 3D polymer network to increase dewatering efficiency, leaving behind valuable materials such as lipids. This article explored the influences of DS particle size on lipid yield and the effects of extraction on the chemical, morphological, and thermal properties of the residual dewatered sludge (RDS). Lipid yields with unimodal distribution were observed across the particle size ranges (<0.5, 0.5–1.0, 1.0–2.0, 2.0–4.0, and 4.0 mm). The highest lipid yield of 1.95% was extracted from 1.0–2.0 mm after 4 h at 70 °C and 0.1 g/mL sludge-to-solvent ratio. Efficiency was influenced by the DS’s morphology, facilitating solvent infiltration and pore diffusion. The extraction process reduced water and organic fractions, resulting in higher thermal stability. Bibliometric analysis of “extraction*” and “sewage sludge” shows increasing research interest from 1973 to 2024. Five research clusters were observed: heavy metal speciation and stabilization, sludge and its bioavailability, extraction techniques and resource recovery, contaminants remediation, as well as phosphorus recovery and agricultural applications. These clusters highlight the diverse approaches to researching DS and RDS while promoting sustainable waste management.

Hydrothermal carbonization of coking sludge: Migration behavior of heavy metals and magnetic separation performance of hydrochar

This study comprehensively investigated the migration behavior and environmental risk of heavy metals (HMs) during the hydrothermal carbonization (HTC) of coking sludge (CS). The results indicated that over 90 % of HMs accumulated in the coking sludge hydrochar (CHC). The decomposition and loss of organic matter led to an increased concentration of HMs with rising temperatures. However, HTC also facilitated the transformation of HMs from bioavailable fractions to more stable fractions. Higher hydrothermal temperatures positively influenced the control of HMs' environmental risks. Ecological risk assessments revealed that the Potential Ecological Risk Index (RI) values of HMs in CHC decreased from 631.15 to 134.23, reaching considerate risk levels. Risk assessment codes indicated that, except for Mn, other HMs were reduced to no risk or low risk after hydrothermal treatment. Furthermore, the magnetic separation performance of CHC was explored, and its practical value was validated using a semi-continuous adsorption-separation device. The results showed that CHC achieved removal rates of 80.41–87.15 % for Congo red (CR) and tetracycline (TC), maintaining stability in various complex water environments. The CHC was rapidly separated after adsorption with a simple magnetic field, achieving a separation and recovery rate of over 80 %. These findings provided theoretical support for the stabilization of HMs in CS and the resource utilization of hydrochar in water treatment applications.

Nano silica-mediated stabilization of heavy metals in contaminated soils

Soil contamination with heavy metals presents a substantial environmental peril, necessitating the exploration of innovative remediation approaches. This research aimed to investigate the efficiency of nano-silica in stabilizing heavy metals in a calcareous heavy metal-contaminated soil. The soil was treated with five nano-silica levels of 0, 100, 200, 500, and 1000 mg/kg and incubated for two months. The results showed that nano-silica had a specific surface area of 179.68 m2/g\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{m}}^{2}/\ ext{g}$$\\end{document}. At 1000 mg/kg, the DTPA-extractable concentrations of Pb, Zn, Cu, Ni, and Cr decreased by 12%, 11%, 11.6%, 10%, and 9.5% compared to the controls, respectively. Additionally, as the nano-silica application rate increased, both soil pH and specific surface area increased. The augmentation of nano-silica adsorbent in the soil led to a decline in the exchangeable (EX) and carbonate-bound fractions of Pb, Cu, Zn, Ni, and Cr, while the distribution of heavy metals in fractions bonded with Fe–Mn oxides, organic matter, and residue increased. The use of 1000 mg/kg nano-silica resulted in an 8.0% reduction in EX Pb, 4.5% in EX Cu, 7.3% in EX Zn, 7.1% in EX Ni, and 7.9% in EX Cr compared to the control treatment. Overall, our study highlights the potential of nano silica as a promising remediation strategy for addressing heavy metal pollution in contaminated soils, offering sustainable solutions for environmental restoration and ecosystem protection.

In-situ halloysite coupled with ex-situ nano-aluminosilicate on heavy metals fate during pyrolysis of solid wastes in a rotary kiln and potential application of pyrolysis residue

During the pyrolysis of heavy metal-containing solid waste, the immobilization and stabilization of heavy metals (HM) is of great significance for its safe disposal and resource utilization of pyrolysis products. This study aims to enhance the enrichment and stability of HMs in pyrolysis residues from HM-containing solid waste in a rotary kiln by combining in-situ halloysite (Hal) with ex-situ nano-aluminosilicate (NC2.6). With 13 % Hal and 10 % NC2.6, the relative retention rate of Cd, Pb, Zn, Cu, and Cr increased by 4.82 %, 29.45 %, 20.98 %, 1.71 %, and 2.61 %, respectively, at 700 ℃. Bureau Communautaire de Référence (F4 > 85 %) and Toxicity Characteristic Leaching Procedure (7.536 mg/L at 10 % addition ratio) extraction results showed that NC2.6 adsorption products exhibit low toxicity, suitable for landfill disposal. The mobility of HMs in pyrolysis residues significantly decreased with increasing temperature and Hal addition. At 13 % Hal addition, low-risk pyrolysis residue (RI = 22.23) was obtained at 700 ℃. Dynamic adsorption experiments evaluated the feasibility of using this pyrolysis residue for methylene blue (MB) adsorption. Under the conditions of a 6 cm adsorption column height and a solution flow rate of 2.5 mL/min, the HM concentration in the effluent met relevant standards, and the adsorption capacity reached 22.733 mg/g. Furthermore, DFT simulations explored the effect of HMs in biochar on MB adsorption, revealing that the adsorption energy between Zn and N reached −281.03 kJ/mol, significantly lower than that of common oxygen-containing functional groups (COC, CO, HOCO, and OH), indicating more stable adsorption. The findings of this research offer novel insights into the immobilization of HMs during the pyrolysis of HM-containing solid waste and resource utilization of HM-containing pyrolysis residue.

Unlocking the potential: Transforming hazardous waste into solid cementitious materials

Incineration fly ash and mineral slag represent hazardous and industrial solid wastes necessitating immediate remediation in China. The liberation and stabilization of heavy metals have erected formidable barriers to their reclamation and repurposing. This study presents a pivotal technology for creating all-solid waste cementitious materials, with the optimal parameters consisting of a dosage of 55.773% incineration fly ash, 38.822% cementitious materials dosage, and 5.405% adhesive powders dosage. Furthermore, a comprehensive evaluation model has been developed to assess the performance of these materials. Several extraction procedure experiments were conducted to investigate the leaching behavior of heavy metals under various leaching scenarios, which suggests the diffusion coefficients of heavy metals under the optimal ratio are all less than 3 × 10–13 m2/s, affirming the effective stabilization and the absence of potential migration risks. The primary mechanisms of solidification involved include ion exchange reactions for charge balance and the encapsulation of precipitates through cementation, both of which contribute to the solidification of heavy metals. The findings will illuminate advanced strategies for reducing waste, enhancing resource efficiency, and promoting environmentally friendly building practices, as well as provide a promising avenue for achieving sustainability goals in construction projects, leading to reduced environmental impact and improved long-term sustainability. The integration of ACM-SW can pave the way for transformative advancements in sustainable building practices, ultimately leading to a more environmentally friendly and resilient built environment.

B-nZVI optimization of strength and heavy metal stability of lead-contaminated soil solidified by Portland cement.

Traditional cement solidifying or stabilizing heavy metal-contaminated sites often face issues like alkalinity loss, cracking, and poor long-term performance. Therefore, bentonite-supported nano-zero-valent iron (B-nZVI) was introduced to optimize the remediation effect of cement in this paper. The effects of B-nZVI, ordinary Portland cement (OPC), and B-nZVI + OPC on the chemical stability of heavy metals and the physical strength of lead-contaminated soil were compared using semi-dynamic leaching methods, BCR tests, unconfined strength analysis, and micro-assisted analysis. Results demonstrated that the addition of B-nZVI effectively enhanced the remediation efficacy of OPC on lead-contaminated soil. The combination of B-nZVI and OPC exhibited a synergistic repair effect, offering superior physical strength and chemical stability for lead remediation. B-nZVI facilitated the adsorption and enrichment of Pb2+, thereby reducing oxidizable lead and enhancing short-term stabilization. Meanwhile, OPC precipitation and silicate gelling stabilized exchangeable lead into the residual form, necessitating repeated hydration gelling. Additionally, B-nZVI's sealing effect via water absorption delayed the leaching of exchangeable lead, thereby reducing lead migration. Even with only 1% B-nZVI added to the 12% OPC base, the leaching amount of Pb2+ decreased significantly from 67.6 to 6.59mg/kg after 7 d of curing. The unconfined strength of contaminated soil treated with the composite solidifying agent for 7 d was 12.87% higher than that of OPC alone, and for 28 d, it was 36.48% higher. This optimization scheme presents a promising approach for effective and sustainable remediation of heavy metal-contaminated sites.

Investigation on the carbonation and heavy metals stabilization of MSWI fly ash by incorporating γ-C2S and Portland cement

Accelerated carbonation is an effective method for treating municipal solid waste incineration fly ash (MSWI FA). However, the CO2 sequestration efficiency and the heavy metals (HMs) stabilization efficiency in accelerated carbonation are limited. In this study, γ-C2S was introduced to enhance the sequestration efficiency of CO2 and the stabilization of HMs in MSWI FA. The study revealed that the inclusion of γ-C2S significantly improved the compressive strength of the samples, leading to a 400 % increase in strength compared to the hydrated samples. The introduction of γ-C2S increased the CO2 uptake of MSWI FA blended samples and reduced the leaching concentration of HMs. The experimental CO2 uptake after powder carbonation exceeded expectations. The carbonation of γ-C2S and MSWI FA produced finer calcite particle size, which could act as seeds to enhance the carbonation reaction. This study offers a solution for the environmentally friendly and zero-carbon preparation of gelling material from MSWI FA.

Effect of hydrochar from sludge mixed with coffee grounds on the immobilization of Cu, Cr and Ni in soil

ABSTRACT In this study, hydrochars were prepared at varying temperatures with distinct mixing ratio, and then the hydrochars were characterized and evaluated for heavy metals to ascertain its potential as a soil conditioner. The application of elevated temperatures resulted in a reduction in the yield of hydrochars, whereas the incorporation of coffee grounds led to an increase in the yield. The blended hydrochar displays elevated ash, fixed carbon, and diminished H/C, O/C, and (O + N)/C ratios, indicating enhanced stability in soil treatment and potential for enhanced soil fertility. The application of hydrothermal carbonization facilitated the stabilization of heavy metals within the sewage sludge, with the stabilizing effect being enhanced by the addition of coffee grounds. Following the application of SCC as a soil conditioner to the heavy metal-contaminated soil for a period of 90 days, it was observed that the heavy metals Cu, Cr, and Ni present in the contaminated soil underwent a transition from an unstable to a stable speciation. Of the treatments tested, AK15 was identified as the most effective, demonstrating a significant reduction in the risk of leaching and biotoxicity associated with Cu, Cr, and Ni in the contaminated soil.

Selective lead capture using amide-containing COFs: A novel strategy for efficient soil remediation

A critical consideration in the application of phytoremediation to remediate sludge soil contaminated with heavy metals is the potential for leaching risks that prevail prior to the efficient uptake of these metals by plants. The most cost-effective method is to use heavy metal stabilizers with selective adsorption. A novel amide-based COF material (COF-TH) has been synthesized as a heavy metal stabilizer for Pb. COF-TH exhibits significant selectivity for Pb in five-metal-mixed solutions, with a distribution coefficient KD as high as 3279 mL·g–1, which was more than 7.3 times that of other heavy metals. The maximum adsorption capacity of COF-TH for Pb was 189 mg·g–1. The adsorption fitted Langmuir model and intra-particle diffusion model, and satisfied pseudo-second-order kinetic model. The excellent selectivity and adsorption performance originate from the complexation between abundant amide groups and Pb ions. Pot experiments and leaching assays confirm that COF-TH decreased Pb leachate concentrations by 77.8 % without significantly decreasing total phytoextracted amounts of other heavy metals, due to the high selectivity of COF-TH to Pb. Additionally, its positive impact on plant growth and microbial diversity makes it a promising soil remediation agent. This investigation offers a novel approach to mitigate the leaching risk of a specific heavy metal Pb during sludge land application by integrating soil phytoremediation with stabilization techniques.

Sustainable utilization of mine wastes in mortar production as a part of aggregates: a case study on calcareous wastes of Angoran lead and zinc mine.

This study investigated the feasibility of large-scale utilizing calcareous wastes (CW) of Angoran lead and zinc mine as aggregates in mortar production with the maximum possible substitution of natural aggregates. The main goal was to produce mortar (concrete with fine aggregates as fine as sand or smaller) from Angoran mine's calcareous wastes for maintenance in its underground spaces.Compared to concrete, suchmortars with better fluidity can enter narrow spacesmore easily.In addition,it can be usedto build various structures around the mine. Therefore, multiple samples were prepared by replacing 0% (as the control sample), 20%, 40%, 60%, 80%, and 100% of natural aggregates with CW. Subsequently, compressive strength, flexural strength, water absorption, slump, and TCLP tests were conducted on these samples. The results revealed that the mortar sample with 80% CW exhibited significantly higher compressive strength at 3, 14, 28, and 56days compared to both the control sample and other samples. Specifically, the compressive strength of this sample reached 35.5MPa at 56days, representing an 18.4% increase over the control sample. This indicates that the hydration of cement and the growth of C-S-H gel were enhanced. Analysis of the workability and slump of the samples indicated that as the percentage of natural aggregate replaced by CW increased, the fluidity of the mortar slightly decreased. In addition to mechanical properties like compressive strength, environmental aspects like heavy metal stabilization are also very important. So, TCLP tests conducted on the four heavy metals lead, zinc, copper, and cadmium demonstrated that the released amounts of these elements from all the samples were below the EPA standard limits. These findings confirm the effective stabilization of heavy metals in mortar samples. A comparison of SEM images revealed that the mortar sample made with 20% CW (with minimum compressive strength) exhibited a higher presence of ettringite compared to the sample made with 80% CW (with maximum compressive strength) after 28days.

Comparison and mechanism analysis of MgO, CaO, and Portland cement for immobilization of heavy metals in MSWI fly ash

The significant production of municipal solid waste incineration fly ash (MSWI FA) underscores the importance of developing efficient solidification materials. This study employed MgO and CaO for immobilizing MSWI FA (with a 70% fly ash incorporation), and the immobilization effect was compared with that of Portland cement (PC). Experimental findings revealed that MgO exhibited the most effective stabilization for heavy metals (Cd, Cu, Pb, and Zn) compared to CaO and PC. XRD, FTIR, TG, and SEM analysis indicated that the principal hydration products in MSWI FA binders solidified with MgO, CaO, and PC were Mg(OH)2, CaCO3, and C-S-H gel, respectively. Mg(OH)2 efficiently immobilized heavy metals through chemical complexation and surface adsorption mechanisms. The MgO-treated MSWI FA demonstrated the highest residual fractions and the lowest easily leachable fractions. Moreover, the leaching characteristics of heavy metals were significantly influenced by the pH level, so MgO-treated MSWI FA with a leachate pH of 9.18 achieved the precipitation and stabilization of most heavy metals. In summary, this study provided an effective material selection for MSWI FA immobilization and presented a novel strategy for MSWI FA management.

Ex Situ Stabilization/Solidification Approaches of Marine Sediments Using Green Cement Admixtures.

The routine dredging of waterways produces huge volumes of sediments. Handling contaminated dredged sediments poses significant and diverse challenges around the world. In recent years, novel and sustainable ex situ remediation technologies for contaminated sediments have been developed and applied. This review article focuses on cement-based binders in stabilizing contaminants through the stabilization/solidification (S/S) technique and the utilization of contaminated sediments as a resource. Through S/S techniques, heavy metals can be solidified and stabilized in dense and durable solid matrices, reducing their permeability and restricting their release into the environment. Industrial by-products like red mud (RM), soda residue (SR), pulverized fly ash (PFA), and alkaline granulated blast furnace slag (GGBS) can immobilize heavy metal ions such as lead, zinc, cadmium, copper, and chromium by precipitation. However, in a strong alkali environment, certain heavy metal ions might dissolve again. To address this, immobilization in low pH media can be achieved using materials like GGBS, metakaolin (MK), and incinerated sewage sludge ash (ISSA). Additionally, heavy metals can be also immobilized through the formation of silicate gels and ettringites during pozzolanic reactions by mechanisms such as adsorption, ion exchanges, and encapsulation. It is foreseeable that, in the future, the scientific community will increasingly turn towards multidisciplinary studies on novel materials, also after an evaluation of the effects on long-term heavy metal stabilization.

Study on the Stability of Heavy Metals in Ceramsite Prepared Using Contaminated Soil

Study on the Stability of Heavy Metals in Ceramsite Prepared Using Contaminated Soil

Environmental remediation potential of a pioneer plant (Miscanthus sp.) from abandoned mine into biochar: Heavy metal stabilization and environmental application

Pyrolysis stands out as an effective method for the disposal of phytoremediation residues in abandoned mines, yielding a valuable by-product, biochar. However, the environmental application of biochar derived from such residues is limited by the potential environmental risks of heavy metals. Herein, Miscanthus sp. residues from abandoned mines were pyrolyzed into biochars at varied pyrolysis temperatures (300–700 °C) to facilitate the safe reuse of phytoremediation residues. The results showed that pyrolysis significantly stabilizes heavy metals in biomass, with Cd exhibiting the most notable stabilization effect. Acid-soluble/exchangeable and reducible fractions of Cd decreased significantly from 69.91 % to 2.52 %, and oxidizable and residue fractions increased approximately 3.24 times at 700 °C. The environmental risk assessment indicated that biochar pyrolyzed over 500 °C pose lower environmental risk (RI < 30), making them optimal for the safe utilization of phytoremediation residues. Additionally, adsorption experiments suggested that biochars prepared at higher temperature (500–700 °C) exhibit superior adsorption capacity, attributed to alkalinity and precipitation effect. This study highlights that biochars produced by pyrolyzing Miscanthus sp. from abandoned mines above 500 °C hold promise for environmental remediation, offering novel insight into the reutilization of metal-rich biomass.

The influence of the pre-addition of semi-dry and dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of MSWI fly ash

Incineration is a main way to dispose the municipal solid waste (MSW) in China, but municipal solid waste incineration (MSWI) fly ash will negatively impact the environment and human health as containing high content of heavy metals. This study aimed to investigate the influence of the pre-addition of dry/semi-dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of fly ash. This study has found that semi-dry slaked lime had more effect on the solidification rate of heavy metals in MSWI fly ash compared to the pre-addition of the dry slaked lime. As the dosage of semi-dry slaked lime increased, the solidification rate of Zn and Ba increased to 100 %, while the solidification rate of Cr decreased to as low as 0 %. However, the effect of the dosage of semi-dry slaked lime on the other heavy metals (Cu, Pb, Cd, Ni) showed a complex trend. This study underscores the importance of the pre-addition of slaked lime during the purification of flue gas in influencing subsequent chelation and solidification treatment of MSWI fly ash. It provides valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices.

Preparation of a New Heavy Metal Chelating Agent and Its Removal of Copper Ions in Wastewater

In this study, a new type of dithiocarbamate (DTCs) heavy metal chelating agent MF-DTC was prepared by carbon disulfide modified melamine formaldehyde resin prepolymer, and the structure of the chelating agent and chelating products was characterized by infrared, ultraviolet, elemental analysis, thermogravimetry, scanning electron microscopy and other means: the process of chelating agent Cu was studied, and the results showed that MF-DTC chelating agent had a higher adsorption capacity, and compared with the traditional chelating agent SDD and Na2S, it had higher chelating capacity under acidic conditions, it can be directly used to treat heavy metals in acidic wastewater. Moreover, the environmental stability of heavy metals after chelation is high. Heavy metals are not easy to be leached again after treatment.

Spatial distribution of sediment dissolved organic matter in oligotrophic lakes and its binding characteristics with Pb(II) and Cu(II).

Dissolved organic matter (DOM), the most active component in interstitial waters, determines the stability of heavy metals and secondary release in sediments. However, little is known about the composition and metal-binding patterns of DOM in interstitial water from oligotrophic lakes affected by different anthropogenic perturbations. Here, 18 interstitial water samples were prepared from sediments in agricultural, residential, tourist, and forest regions in an oligotrophic lake (Shengzhong Lake in Sichuan Province, China) watershed. Interstitial water quality and DOM composition, properties, and Cu(II)- and Pb(II)-binding characteristics were measured via physicochemical analysis, UV-vis spectroscopic, fluorescence excitation-emission matrix-parallel factor analysis (EEM-PARAFAC), and fluorescence titration methods. The DOM, which was produced mainly by microbial activities, had low molecular weights, humification degrees, and aromaticity. Based on EEM-PARAFAC results, the DOM was generally composed of tryptophan- (57.7%), terrestrial humic- (18.7%), microbial humic- (15.6%), and tyrosine-like (8.0%) substances. The DOM in the metal complexes was primarily composed of tryptophan-like substances, which accounted for ~42.6% of the DOM-Cu(II) complexes and ~72.0% of the DOM-Pb(II) complexes; however, microbial humic-like substances primarily contributed to the stability of DOM-Cu(II) (logKCu = 3.7-4.6) and DOM-Pb(II) (logKPb = 4.3-4.8). Water quality parameters did not significantly affect the stability of DOM-metal complexes. We demonstrated that the metal-binding patterns of DOM in interstitial water from oligotrophic lakes are highly dependent on microbial DOM composition and are affected by anthropogenic perturbations to a lesser extent.

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.

Co-pyrolysis of municipal sludge and papermaking sludge: Pyrolysis behaviors and heavy metals immobilizations

The co-pyrolysis of municipal sludge (MS) and papermaking sludge (PS) is beneficial for improving the quality of co-pyrolysis biochar and the stability of heavy metals in it. This study investigated the synergistic effect of co-pyrolysis of MS and PS, as well as the influence of different mass ratios (1:9, 3:7, 5:5, 7:3, and 9:1; MS:PS) and pyrolysis temperatures (400–600 ℃) on the physicochemical properties of pyrolysis char, chemical speciation of heavy metals, and their potential ecological risk index. Furthermore, thermodynamic equilibrium calculations were used to study the transformation and stabilization mechanisms of heavy metals during co-pyrolysis. The results indicated that the addition of PS increased the comprehensive pyrolysis index of MS (by 2.09–16.72 times) and the specific surface area of co-pyrolysis char. The inclusion of MS effectively promoted the transformation of heavy metals from unstable fractions to stable fraction, significantly reducing the potential ecological risk index of pyrolysis biochar (by 21.93–41.58 %). The combination of thermodynamic equilibrium calculations and experimental data demonstrated that heavy metals in sludge could be stabilized through the formation of stable heavy metal compounds or their encapsulation within the lattice of inorganic components during co-pyrolysis. These findings suggest that co-pyrolysis of MS and PS is a feasible and promising approach for producing high-quality pyrolysis char with low risk of heavy metals.

Advancements in Heavy Metal Stabilization: A Comparative Study on Zinc Immobilization in Glass-Portland Cement Binders.

Recent literature has exhibited a growing interest in the utilization of ground glass powder (GP) as a supplementary cementitious material (SCM). Yet, the application of SCMs in stabilizing heavy metallic and metalloid elements remains underexplored. This research zeroes in on zinc stabilization using a binder amalgam of GP and ordinary Portland cement (OPC). This study juxtaposes the stability of zinc in a recomposed binder consisting of 30% GP and 70% OPC (denoted as 30GP-M) against a reference binder of 100% CEM I 52.5 N (labeled reference mortar, RM) across curing intervals of 1, 28, and 90 days. Remarkably, the findings indicate a heightened kinetic immobilization of Zn at 90 days in the presence of GP-surging up to 40% in contrast to RM. Advanced microstructural analyses delineate the stabilization locales for Zn, including on the periphery of hydrated C3S particles (Zn-C3S), within GP-reactive sites (Si*-O-Zn), and amid C-S-H gel structures, i.e., (C/Zn)-S-H. A matrix with 30% GP bolsters the hydration process of C3S vis-à-vis the RM matrix. Probing deeper, the microstructural characterization underscores GP's prowess in Zn immobilization, particularly at the interaction zone with the paste. In the Zn milieu, it was discerning a transmutation-some products born from the GP-Portlandite reaction morph into GP-calcium-zincate.