Leaching Values Research Articles

Target immobilized phases of heavy metals in hazardous waste based lightweight aggregate

The potential leaching risk poses a concern for the large-scale recycling of hazardous waste as lightweight aggregates (LWAs). This paper investigated the combination state of heavy metals in target immobilized phases of LWA through both theoretical calculations and experimental verification. Results reveal that Pb can enter the feldspar crystal cell to form stable interstitial solid solutions, while Cu, Cr, and Ni can replace specific ions in spinel to form replacement solid solutions. The addition of target immobilized phases generally weakened the physical performance of LWAs, while reducing the leaching risk. The appropriate amount of the spinel phase favored the immobilization of Cu, Cr, and Ni, whereas albite contributed to the immobilization of Pb with low leaching values. Due to the lower melting temperature, albite could facilitate the introduction of a high-temperature liquid phase, enhancing the migration of Pb²⁺ for better immobilization in glassy phase. In contrast, anorthite exhibited a higher viscosity at 1100 °C, leading to ineffective physical encapsulation of heavy metal ions by the liquid phase. Heavy metal ions react with additional spinel phase at high temperatures to form stable solid solution phases. This study provides a novel method for regulating heavy metal leaching in hazardous waste-based LWA.

Recovery potential of municipal solid waste incineration bottom ash graded by particle size in an alkali-activated cementitious material system: Curing properties and environmental leaching risk

Currently, municipal solid waste incineration bottom ash (MSWI BA) is considered for use in alkali-activated cementitious materials (AACMs). However, a comparison of relevant studies revealed large differences in the reaction kinetics performance of MSWI BA. This finding presented difficulties in assessing the use of the MSWI BA in AACM. Compositional differences among particle sizes and design bias caused by the content of reactive components are two of the scientific shortcomings. In this work, MSWI BAs were categorized as S1 (0–2 mm), S2 (2–4 mm), S3 (4–8 mm), and S4 (8–16 mm). The reactivities of S1 to S4 were characterized. The mixing proportions of the AACMs were also designed on the basis of the reactivity components. The results showed that more glassy phases and synthetic ceramics in S4, as well as a lower Ca/Si ratio (1.08) in the final product, increased the strength. The maximum value of the 28 d compressive strength was 36.4 MPa. Among the final AACM products, most of the compressive strengths of AS1 and AS2 developed early, with strength increases of 3.1 % and 15.1 %, respectively, over the 7–28 d process. In addition, the Ca/Si ratios of C–S–H in AS1 and AS4 deviated slightly from the design values of 7.3 % and 4.6 %, respectively. The final product exhibited optimized pore distribution and densification, highlighting the physical encapsulation effect on toxic elements. Moreover, the leaching values of heavy metal elements are within the permissible range of Chinese standards.

Investigation on the leaching behavior of natural aggregates using percolation test and total content.

In the construction industry, environmental behavior of aggregates has been monitored thanks to leaching tests, especially for alternative aggregates obtained from waste (e.g., construction and demolition waste, MSWI). Few studies were carried on the leaching behavior of natural aggregates, which are often not regulated for their substance release in most EU member states (as France). Leachable content of some heavy metals, halides, and sulfates on natural aggregates was investigated using up-flow percolation test EN 16637-3 and compared to threshold values. Only three samples (NS2, NG1, and NG8) show one element which exceeded threshold values (As, Zn, As, respectively), among the 19 natural aggregates tested for leaching. In this study, three natural aggregates (NG1, NS1, NS2) have been chosen because of their measurable leaching values. Total content was obtained through acid digestion. Influence of grain size on leaching results was investigated. Predominant release mechanisms were determined using EN 16637-3 - Annex D, based on percolation results such as pH, electrical conductivity, and leached content, and were then discussed. Detailed results for releases of As, Ba, Ni, Zn, SO42-, and F- were investigated. EN 16637-3 - Annex D shows some limits, especially for trace elements. The pH was found to be one of the most important factors influencing leaching release of most elements, being more important than grain size. By comparing total content with released quantities, it has been shown that As and Mo in NS2 are easily leached, hence present in a very soluble chemical form. Determining release mechanisms accurately in this study seems only possible for elements present in significant amounts.

Properties of products obtained in the process of solidification and stabilization of fly ash resulting from thermal treatment of sewage sludge

The article presents an analysis of the results of research on the composition of fly ash from the thermal processing of sewage sludge [SSA] collected from three incineration plants located in Warsaw, Cracow and Łódź. It determines the leaching values of selected heavy metals from the tested fly ash and ordinary class concrete C20/25 with partial replacement - up to 20% of cement with fly ash. The laboratory tests performed showed that they have a comparable granulometric composition. In contrast, the physico-chemical properties of the tested fly ashes differ from ashes from coal combustion traditionally used in concrete technology. SSA is characterized by an average lower content of silicon, iron, and aluminium oxides with a much higher content of phosphorus oxides. Leaching tests indicate low mobility of heavy metals, meeting Polish regulations regarding the possibility of using SSA in construction for specific applications. At the same time, they do not pose a significant threat to human health or the environment. Construction waste containing SSA may be disposed of in inert waste landfills.

Study on environmental characteristics of sustainable biomimetic soil preparation and its application in gangue reclamation

To address the key challenges in achieving large-scale ecological reclamation of coal gangue in situ, this study utilized loess from a mining area in Northwest China to prepare a biomimetic soil. A new inorganic curing agent (ISA) was developed using coal-based solid waste and cement. The study investigates the influence of different ISA dosages and their interaction with Polyacrylamide (PAM) on the environmental characteristics of biomimetic soil, including geotechnical, ecological, and heavy metal stabilization properties. Results indicate that the addition of ISA significantly enhanced the geotechnical performance of the in-situ soil, with unconfined compressive strength exceeding 350 kPa when ISA content was above 6 %. Soil evaporation experiments and soil water characteristic curve tests demonstrated that a 6 % ISA dosage combined with 0.05 ‰ PAM could maintain soil's good water retention capability while preserving a bimodal pore structure. The biomimetic soil exhibited effective stabilization of heavy metals, including Pb, Zn, Cu, and As. The particles of PAM and the hydration products of ISA not only filled soil pores and increased soil strength but also adsorbed, encapsulated, and immobilized heavy metals. “Biomimetic soil-gangue” leaching test results confirmed that the gangue samples treated with biomimetic soil met the standards for Class III underground water in China regarding heavy metal leaching values. This study provides an effective solution for the large-scale in-situ disposal and resource utilization of gangue in Northwestern mining areas of China.

Effect of ball milling-Ca(OH)2 coupling activation on the cementitious properties of ferrous extraction tailing of nickel slag: Basic properties, hydration mechanism and heavy metal safety

In order to improve the reactivity of ferrous extraction tailing of nickel slag (FETNS), This paper delves into the influence of ball milling-activator Ca(OH)2 on the cementitious activity of FETNS. Furthermore, it assesses the combined activation's impact on the working performance, mechanical properties, shrinkage properties, early hydration process, hydration products, and heavy metal element leaching of the FETNS-OPC composite cementitious system. The results show that the coupling activation significantly enhanced the reactivity of FETNS and prolonged the acceleration period of the composite cementitious system during the hydration process, thereby promoting the hydration reaction. This not only shortened the setting time of the composite cementitious system, but also significantly improved its early compressive strength. The microscopic test results showed that the coupling activation improved the reaction degree of the composite cementitious system, promoted the formation of more reaction products, and increased the compactness of the internal structure. In addition, the coupling activation also enhanced the degree of polymerization of the composite cementitious system, and these factors together led to an increase in compressive strength. However, it is worth noting that with the increase of FETNS reactivity under the coupling activation, the autogenous shrinkage change rate and drying shrinkage change rate of the composite cementitious system also increased accordingly. Finally, the results of the heavy metal leaching test showed that the coupling activation reduced the leaching value of heavy metal elements in FETNS, ensuring the safety of practical application.

Carbon sequestration through mineral carbonation: Using commercial FGD-gypsum from a copper smelter for sustainable waste management and environmental impact mitigation

In this study, we conducted a comprehensive examination of a commercial FGD gypsum produced in a Copper (Cu) smelter process and delved into its potential use as a Calcium (Ca)-rich material for ex-situ mineral carbonation by exploring the partitioning and fate of these metal impurities. The resulting carbonation end-product displayed a calcium carbonate (CaCO3) content of 71.1%, featuring a relatively low CO2 conversion, which may be attributed to the presence of metallic impurities in the commercial FGD-gypsum. Most of these metallic impurities, acting as inputs to the carbonation process, originate from the parent FGD-gypsum matrix. This results in an increased ionic strength within the FGD gypsum, potentially impeding the diffusion of carbon dioxide (CO2) from the gas phase to the aqueous phase. The partitioning and examination of the speciation of major, minor, and trace elements at all stages of CO2 conversion allowed us to propose four potential reaction pathways influencing carbonation efficiency: (i) the formation of metal carbonates, (ii) the production of metal oxides and oxyhydroxides, (iii) the development of metal multiform compounds, and (iv) elements deviating from the outlined patterns. Commercial FGD-gypsum is suitable for acceptance at non-hazardous waste landfills. However, it's essential to highlight that leaching values of As exceed the inert range and non-hazardous waste standards in commercial FGD-gypsum. Although most heavy metal leaching values from the carbonate end-product stay below non-hazardous limits, the release of some heavy metal leachates from the carbonate end-product may limit reuse options for these materials.

The preparation and formation mechanism of ferrochrome slag-based high-strength ceramic aggregate and its impact on the performance of concrete

Solid waste, such as ferrochrome slag (FCS), has been extensively studied for its potential use as a construction material. This research focuses on utilizing FCS as the primary raw material to produce a high-strength ceramic aggregate, referred to as FCS-HSCA. The impact of calcination parameters on the performance of FCS-HSCA was investigated, while the underlying transformation mechanism was comprehensively explored. Subsequently, concrete with FCS-HSCA was prepared, and its influence on the performance of concrete was evaluated. The results reveal that the optimal performance of FCS-HSCA is achieved with a compressive strength of 310.3 MPa, a water absorption of 0.27%, and an apparent density of 2930 kg/m3. These characteristics are associated with specific parameters during the calcination stages, namely a preheating temperature of 1100 ℃, preheating time of 60 min, calcination temperature of 1500 ℃, and calcination time of 180 min. Moreover, the increased crystalline phases promote the solid dissolution of chromium into Mg(Al1.5Cr0.5)O4, and the occurrence state of chromium is stable during the preparation of FCS-HSCA. This results in a decreased leaching value from 0.439 mg/L to 0.188 mg/L, reducing the impact on the environment and human health. Additionally, replacing FCS with FCS-HSCA in concrete enhances its compressive strength from 59.9 MPa to 66.1 MPa. This improvement is attributed to a notable reduction in the diameter of pores on the surface of FCS-HSCA, leading to a denser structure and improved bondability with cementitious composites. Finally, this novel approach maximizes the utilization of material characteristics while enhancing the stability of waste FCS.

Optimization of Controlled Low-Strength Material from Multi-Component Coal-Based Solid Waste

Recently, controlled low-strength material (CLSM) has been considered an easy-to-mix material, and the raw material is usually derived from solid waste, suggesting lower production costs. Moreover, the resource utilization of waste fosters the sustainable advancement of both society and the environment. In the present work, a CLSM with excellent performance was developed by adopting fly ash, bottom ash, desulfuration gypsum, and cement as the main cementitious materials, as well as gasification coarse slag and coal gangue as aggregates. An orthogonal experiment with three factors and three levels was designed according to the ratio of cement to binder, the contents of water, and the water-reducing agent. Further, the macroscopic properties of flowability, dry density, bleeding, compressive strength, fresh density, porosity, and absorption rate of the CLSM mixtures were tested. To optimize the CLSM proportion, the ranges of three indicators of CLSM were calculated. Experimental results manifested that the fresh and dry densities of the mixtures were within the range recommended by ACI 229. The optimal levels of cement–binder ratio (i.e., the ratio of cement to binder), water content, and water-reducing agent content are 0.24, 248 kg·m−3, and 0.80 kg·m−3, respectively. Under this condition, the flowability was 251 mm, the bleeding was 3.96%, and the compressive strength for 3 d, 7 d, and 28 d was 1.50 MPa, 3.06 MPa, and 7.79 MPa, respectively. Furthermore, the leaching values of eight heavy metals in CLSM and raw materials were less than the standard requirements, indicative of no leaching risk.

Factors influencing the difference in dissolved ion inputs to the forest floor between deciduous and coniferous stands: comparison under high and low atmospheric deposition conditions

It is necessary to clear the relationship between physical and vegetation factors on the processes governing dissolved ion inputs to the forest floor to estimate correctly the values of atmospheric input to the forest. This study identified the factors influencing the differences in dissolved ion inputs to the forest floor between coniferous evergreen and broad-leaved deciduous species by analyzing the phenological variations of dry deposition and canopy exchange calculated by the canopy budget model under a high-deposition site near the city of Tokyo and a low-deposition site 84 km further away. At low-deposition site, vegetation factors such as capture efficiency did not explain the differences in Na+ or Cl− dry deposition. Leaf physiological characteristics influenced the differences in the Mg2+ and Ca2+ canopy leaching values, and phenology, leaf wettability, and diffusion processes from water film into leaves influenced the differences in NH4+ and NO3− input processes between tree types. At the high-deposition site, differences in the dry deposition of Na+, SO42−, Cl−, Mg2+, Ca2+, NH4+, and NO3− between tree types were influenced by differences in capture efficiency between coniferous and broad-leaved canopies in the leafed period and by the absence of leaves in deciduous species after leaf fall. These results indicated that atmospheric deposition affected the capture efficiency of coniferous trees for dry deposition and enhanced the difference of dissolved ion inputs to the forest floor between coniferous and deciduous species.

Optimizing biochar-based geopolymer composites for enhanced water resistance in asphalt mixes: an experimental, microstructural, and multi-objective analysis

Due to increased traffic and environmental concerns, this study addresses challenges in conventional asphalt concrete. Our focus is on enhancing the water resistance of asphalt mixes through the optimization of both the asphalt binder and the biochar-based geopolymer composite. We employ experiments and response surface methodology to assess their impact on volume, Marshall parameters, and water resistance. Asphalt binders were evaluated within the range of 4–6%, while biochar-based geopolymer composite levels varied from 0 to 4%. According to the findings, the incorporation of the biochar-based geopolymer composite improves asphalt properties, stiffness, and temperature sensitivity. Response surface methodology (RSM) was utilized to construct robust mathematical models with high R2 values (90%) and low p-values. Multi-objective optimization indicated that optimal content levels were 4.56% for the binder and 2.71% for the biochar-based geopolymer composite. Model accuracy was confirmed with less than a 5% error in validation tests. The research also identified structural changes in the asphalt binder caused by the BGC Si–O phase. Additionally, the leaching value for both BGC and BGC-MAB asphalt concrete was found to be substantially below the regulatory limit, demonstrating the environmental safety of incorporating BGC into the asphalt sector.

Controlled Drainage Effectiveness in Reducing Nutrient Outflow in Light of Climate Changes

This modeling study focused on the hydrological and water quality effects of controlled drainage (CD) when operated using a subsurface drainage system in an agricultural field in the Wielkopolska region. The DRAINMOD hydrologic model was well calibrated and validated in an experimental field. This model was used in the performance of CD and free drainage (FD) combinations (108 and 27, respectively) in a near-future climate change scenario. The objective was to understand the potential of CD on the groundwater table (GWT), drainage outflow, surface runoff, and nitrogen and phosphorus reduction under projected climate conditions in Poland during the 21st century with shared socioeconomic pathway SSP370. The results indicated that the earliest start of CD practice is the most effective in increasing GWT. Compared to current climatic conditions, when applying CD on 1 March in the near future, with an initial GWT of 60 and 80 cm b.s.l. in wet years, drainage outflows will increase by 33% and 80% for the GFDL model, by 30% and 40% for the MPI model, and by 17% and 23% for the UKESM model. Comparing the surface runoff values obtained to current climate conditions, the MPI, GFDL, and UKESM models predict a significant increase in surface runoff in the near future, which is due to the predicted increase in precipitation. The annual NO3–N reduction was by 22, 19, and 15 kg per hectare for wet, normal, and dry years, respectively, in the near future. Among the climate scenarios, the UKESM model predicted higher NO3–N and PO4 leaching values compared to the MPI and GFDL models.

Carbonation and Leaching Behaviors of Cement-Free Monoliths Based on High-Sulfur Fly Ashes with the Incorporation of Amorphous Calcium Aluminate.

The high sulfate content in various alkaline wastes, including those from fossil fuel and biomass combustion, and other industrial processes, necessitates careful management when used in cementitious systems to prevent potential deterioration of construction materials and environmental safety concerns. This study explores the under-researched area of high-sulfur fly ash (HSFA) utilization in the production of cement-free monoliths through accelerated carbonation and further examines the effect of niobium slag (NS)-a calcium aluminate-containing slag-as an additive on the strength development and the mobility of SO42-. The methodology involves mineralogical and microstructural analyses of monoliths before and after carbonation, accounting for the effects of accelerated carbonation treatment and NS addition. The findings suggest that accelerated carbonation significantly improves the initial compressive strength of the HSFA monoliths and generally immobilizes heavy metals, while the effect on sulfate immobilization can vary depending on the ash composition. Moreover, the addition of NS further enhances strength without substantially hindering CO2 uptake, while reducing the leaching values, particularly of sulfates and heavy metals. These findings suggest that it is feasible to use calcium aluminate-containing NS in HSFA-based carbonated monoliths to immobilize sulfates without compromising the strength development derived from carbonation. This research contributes to the understanding of how accelerated carbonation and NS addition can enhance the performance of HSFA-based materials, providing valuable insights for the development of sustainable construction materials.

Investigation of the water resistance of non-sintered wrap-shell lightweight aggregates with high content solid waste and its application in water permeable bricks

Non-sintered solid waste lightweight aggregates can be used as building materials. However, its active hydration performance has brought challenges to its application. In this study, non-sintered waterproof solid waste wrap-shell lightweight aggregates (W-SWSLAs) were prepared from dredged sediments, steel slag, and other solid waste materials, and activator and waterproof agent were also added. The shell phase of W-SWSLAs was treated with inorganic aluminum salt waterproof agent (IWA) and silicone waterproof agent (SWA), respectively, to investigate the effects of different kinds and dosages of waterproof agents on the properties of the bearing capacity of single grain and water resistance. The performance of W-SWSLAs was assessed from the environmental, physicochemical and mechanical perspectives, respectively. In addition, its application in water permeable bricks was also studied. The results showed that when the addition amount of SWA was 0.08%, it could reach a good balance between the water resistance and mechanical performance of W-SWSLAs. The leaching values of pollutants were well below the limit value set out in the legislation. The water absorption rate, cylinder compression strength and softening coefficient of W-SWSLAs were 8.73%, 20.35 MPa, and 0.84, respectively. The permeability coefficient of water permeable bricks prepared from W-SWSLAs (W-SWSLAPB) was 0.022 cm/s, and the strength loss rate was 10.4% after 25 freeze–thaw cycles, which all met the current Chinese National Standards. The production of W-SWSLAs, whose solid waste content is 95.17 wt%, provides an eco-friendlier approach to converting hazardous and industrial solid waste into high value-added materials.

Production of lightweight foam ceramics by adjusting sintering time and heating rate

The heat treatment system was a key factor in the performance of lightweight foam ceramics. Phosphorus tailings and coal gangue were recovered for preparing lightweight foam ceramics by adjusting the sintering time and heating rate. The goal was to set a reasonable heat treatment regime for maximum optimized performance. The influences of sintering time and heating rate on the phase evolution, pore structure, physical properties and heavy metal solidification of lightweight foam ceramics were investigated by the results of XRD, SEM and ICP-MS examinations and theoretical calculations. As a result, extended sintering time promoted to formation glassy phase, which facilitated the average pore size growth from 34.88 µm to 124.23 µm. The larger heating rate (10 °C/min) prevented the vitrification of lightweight foam ceramics with an increase in water absorption (2.31 % − 23.14 %) and a decrease in compressive strength (9.80 MPa − 3.56 MPa). The lightweight foam ceramics exhibited relatively uniform pore structure, high porosity (61.79 %), low density (0.99 g/cm3), satisfactory compressive strength (10.08 MPa), and low water absorption (2.87 %) when they were treated at 1150 °C for 60 min with the heating rate of 5 °C/min. In particular, the extremely low leaching values of heavy metals and potential ecological risk index were detected for the lightweight foam ceramics. The fabricated lightweight foam ceramics satisfy the strength requirements of Chinese national standards for non-bearing building partitions and non-bearing bricks. This technology not only provided practical guidance for adjusting the sintering process to manufacture high-performance lightweight foam ceramics, but also the simultaneous high value-added utilization of phosphorus tailings and coal gangue could be achieved.

New applications of municipal solid waste incineration bottom ash (MSWIBA) and calcined clay in construction: Preparation and use of an eco-friendly artificial aggregate

The aim of this study is to prepare MSWIBA as eco-friendly artificial aggregates (EFAAs) by cold bond granulation technique using a low carbon limestone calcined clay cement (LC3). The water absorption rate of EFAAs is between 14.42 and 21.82%, and the maximum compressive strength can reach 2.5 MPa. Calcined clay particles can effectively adsorb heavy metal ions after absorbing water, and EFAAs can reduce the leaching value of toxic elements in MSWIBA by more than half on average. Compared to standard OPC cementitious materials, LC3 composites only need 50% of the energy and discharge 43% of the CO2, producing a more environmentally friendly artificial aggregate. In addition, the 28-day compressive strength of concrete was higher than 30 MPa on average after applying EFAAs to concrete. The good application capability shown by EFAAs, as well as their low energy consumption and low carbon environmental characteristics, promote the better application of MSWIBA in buildings.

Valorization of phosphogypsum waste through acid geopolymer technology: synthesis, characterization, and environmental assessment

Phosphogypsum (PG) constitutes the principal by-product of the phosphate industry which largely restricts its wide development. The incorporation of PG as a reinforcement agent into geopolymer cement, can play however a significant role to enhance their mechanical and microstructural properties and to develop a sustainable geopolymer–PG based circular economy. In this study, geopolymer reinforced PG composites were prepared at different PG content according to PG/MK ratio in the range of 0–1. The mechanical properties of the composites were tested under compressive and flexural strength. The results show a significant enhancement of compressive and flexural strength from 40.14 MPa to 48.43 MPa and 5.13 MPa to 9.1 MPa respectively with addition of 20.6 % and 77.3 % compared standalone geopolymer. This improvement was linked systematically with crack self-healing mechanism due to PG rod-like morphology and its high adhesion to the geopolymer matrix. The heavy metals leaching test show that most of the developed acidic geopolymer– PG composites have a leaching value lower than the international recommendations. Thus, geopolymer– PG composites can constitute an efficient and sustainable alternative to conventional building materials and can be extended to divers’ industrial applications.

Recycling Bio-Based Wastes into Road-Base Binder: Mechanical, Leaching, and Radiological Implications

This work presents a physical, mechanical, durability, leaching, and radiological assay of three wastes (egg and scallop shells and olive pomace ash) as road-base binders. Two different waste/Portland-cement ratios (7.5/92.5 and 80/20) were studied. Density and compressive strength decreased when different wastes were added in every proportion. Additions of 7.5% of both shells reduce the density to about 2.5% and the compressive strength to 20%, while 80% reduces the density to 20% and the compressive strength to 90%, while the addition of biomass fly ash decreases the density and compressive strength in a higher proportion than shells. The durability against acid attack is increased when the three wastes are used, and this increase is higher when the waste dosage is increased (up to 15 times more when 80% biomass ash is used). With respect to leaching, scallop and eggshells can be used as a component of hydraulic road binder, but olive pomace ash presents leaching values higher than the limits of different regulations (Se, Pb, Ni, Mo, Cu, and As). From a radiological perspective, all road-base binders present an activity concentration index lower than 1, except when olive pomace ash was used, and the binders showed higher values of 40K due to the high potassium content of fly ash.

Incorporation of Adsorbent Ash with Potentially Toxic Elements into Mortar: A Sustainable Approach

Although biosorption is an effective technique for removing potentially toxic elements (PTEs) from wastewater, it causes secondary pollution in the form of used adsorbents ending up in landfills, leading to PTE leaching into groundwater. This study used two kinds of adsorption process waste ash - adsorbed paper ash (APA) and adsorbed mulch ash (AMA)- as an additive to mortar, which added an environmental and economic value through energy recovery during the ashing process following the ideas of the waste to energy and circular economy, in addition to immobilizing the PTEs into a cement matrix aiming to close the loop of pollution. This study focused on investigating the leaching of PTEs (Cd, Zn, Cu, and Pb) at five different artificial adsorption initial concentrations (0.5, 1, 5, 10, and 50) mg/L and three different mixing weight proportions of ash with cement, as well as their pH-dependent behavior, to ensure environmental safety. To detect the release of PTEs from the mortar ash mixes, the ICP-OES technique was used. The study concluded that the used adsorbent ashes potentially could be environmentally acceptable as an additive for mortar because their ability to stabilize PTEs based on leaching values of (Pb, Zn, and Cu) was below the permissible limit under the nonhazardous waste category. Only Cd leached higher than the regulatory limit in the case of very low acidity when pH was lower than 0.

Hydrometallurgical leaching and recovery of cobalt from lithium ion battery

The main aim of this work was to test the ability of an amino acid (i.e. glycine) to leach cobalt from Li ion batteries (LiBs). The process parameters namely temperature, pulp density and concentration of glycine were optimized for maximizing the leaching efficiency of cobalt from the cathodic material. Response surface methodology (RSM) was applied for determining the experimental conditions instead of using the traditional one factor at a time (OFAT) approach in order to ascertain the interaction effects between the different factors. Thus, the optimal leaching value based on RSM and maximum cobalt leaching potential from LiBs was obtained. The optimum values for the parameters were as follows; temperature = 74 °C, pulp density = 19.9 g/L and glycine concentration = 0.936 M. Under this optimum condition, the cobalt leaching efficiency was 61.8%, while a maximum leaching of 89.7% was achieved at the following conditions: temperature = 100 °C, pulp density = 13.8 g/L and glycine concentration = 1.24 M. Oxalic acid was used for recovering cobalt from the leaching solution by varying the pH and molar ratio of oxalic acid and cobalt ions. Cobalt recovery efficiencies were ∼ 88.0% at pH 7.0 and at oxalic acid to cobalt ion molar ratio of 2.5:1.0. • Glycine in the presence of H 2 O 2 leached Co from spent Li ion batteries. • A maximum of 89% of Co was leached by glycine from LiBs. • Co was selectively recovered using oxalic acid as precipitating agent. • More than 88% of soluble Co can be recovered as Co-oxalate precipitate.