TCLP Test Research Articles

Analysis Of Flexural Resistance And Environmental Feasibility Of Ferrocement Concrete Slabs From Fly Ash And Sandblasting Waste

Sandblasting waste from the shipbuilding industry and fly ash waste from industry and electric steam power plants in Indonesia are relatively high in quantity, are B3, and can potentially cause serious environmental pollution. This research aims to utilize this waste as material for ferrocement concrete, where the SiO2 and Al2O3 content from fly ash replaces some of the cement, silica sand from sandblasting waste replaces sand, and additional wire mesh as reinforcement. The method used is a quantitative experiment, where the material to be used is tested for gradation and TCLP. The finished ferrocement concrete is tested for flexural strength. The test results show that the raw material meets the gradation standards in SNI 03 2834 2000, as well the TCLP test results which show that the B3 heavy metal content is Barium, Zinc, and Copper in the sandblasting waste value is below the quality standards of PP No. 22 of 2021 Appendix XI so that all materials can be used for mix designs. The mix design created has a composition ratio of 1S:1.5PB, 1S:1.5PB:50AT, 1S:2PB, and 1S:1PB:50AT. The 1S:2PB ratio composition has the highest average flexural strength, namely 17.46 MPa, which is suitable for light vertical load construction work

FeAl-LDH-modified biochar (FeAl-LDH@BC): A high-efficiency passivator for hexavalent chromium (Cr(VI)) reduction and immobilization in contaminated soil

A composite FeAl-LDH@BC obtained by successfully loading FeAl-LDH onto biochar (BC) is used to the Cr(VI)-contaminated soil remediation. The efforts of loading, initial pH, concentration and dosage are investigated. The results indicate that the immobilization process of Cr(VI) in soil could be well described by the pseudo-second-order kinetic model and maximum adsorption capacity of FeAl-LDH@BC is 42.78 mg/g at a temperature of 298 K. Additionally, The physicochemical properties of FeAl-LDH@BC are characterized by SEM, EDS, XRD, FTIR and XPS. The characterization results suggest that the immobilization mechanism involved adsorption and reduction. Cr(VI) is immobilized by adsorption to the layers of FeAl-LDH, the reduction of Cr(VI) to Cr(III) is then accomplished using Fe(II) as a reducing agent. In order to demonstrated the stability of composites for environmental restoration, the TCLP tests, dry-wet, freeze-thaw aging cycles, soil phytotoxicity tests, and microbial community are analyzed. The study shows that we provided a material for soil immobilization with high performance for the remediation of Cr(VI)-contaminated soil.

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.

Cement from Copper smelting slag: Compressive strength, microfreeze-thaw tests and microstructural analysis

Copper smelting slag (CSS) are waste slag obtained from smelters after reusing sulphur smelting slag. This study explores the potential of CSS to serve as a resource in cement mortar construction. Specifically, the study investigates the use of mechanical and chemical methods to enhance the volcanic ash activity of CSS, enabling them to replace up to 30 % of the cement content in cement mortar. The modified CSS was analyzed in terms of particle size and (Toxicity Characteristic Leaching Procedure) TCLP testing, while cement mortar specimens were subjected to a battery of tests including compressive strength, Freeze-thaw experiment, TCLP testing and cement stability testing. The results showed that compared with the unmodified CSS material, the copper smelting slag cement material with CaCO3 meets the requirements of GB/T 1596–2017 on the standard compressive strength of OPC 42.5 grade, with a compressive strength of 38.88 MPa at 10 % CaCO3 admixture, among which the CSS cement material with 10 % CaCO3 is the best and meets the leaching toxicity standard. Moreover, the modified CSS reduced energy consumption by 7.15 %, CO2 emissions by 27.41 %, and cost by 19.84 %. XRD, FTIR and SEM analysis showed that the mechanical activation of CaCO3 doping more drastically damaged the crystal structure of CSS, and local lattice distortion occurred, which induced the transformation of CSS from crystalline phase to amorphous phase and destroyed the ordered structure of minerals, resulting in the volcanic ash activity increased. Overall, this study demonstrates that CSS can serve as a viable raw material in cement mortar samples, reducing environmental impact and achieving resourceful use of slag.

Reductive Immobilization of Hexavalent Chromium in Soil Using Hydrazine – Kinetics, Process Optimization, Sonochemical Enhancement, and Cost Estimation

ABSTRACT The presence of hexavalent chromium in soil poses a grave hazard to the environment and human health. This study explores the effectiveness, mechanism, and economic viability of remediation of Cr(VI)-contaminated soil by hydrazine. Soil-phase batch kinetic experiments were performed to examine the feasibility of reducing Cr(VI) while finding the effects of relevant process parameters, such as initial Cr(VI) concentration, hydrazine dosage, pH, soil-to-water ratio, and temperature. The materials were thoroughly characterized to gain insight into the mechanism. TCLP tests were done to affirm the immobilization stability. Complete Cr(VI) reduction was achieved within 3 h using a moderate 326% excess of hydrazine at neutral pH. Sonication of the soil mixed with hydrazine using a probe-type sonicator accelerated the reduction of Cr(VI) to Cr(III). Kinetic data could be adequately fitted in a second-order rate model, where the rate constant shows a linear dependency on the soil-to-water ratio. Additionally, the logarithmic rate constant demonstrates linearity within the pH range. The leaching toxicity of Cr(VI) and Crtotal complied with the USEPA regulatory limit and remained stable for 75 d. Hydrazine alone and its combination with ultrasound are sustainable and economically feasible for effective remediation of Cr(VI)-contaminated soil. The statistical analysis using RSM indicated a 99.4% reduction, aligning closely with the calculated optimized value. The optimal process conditions are easy to implement for field application at a competitive cost compared to other reductants. A simplified economic analysis was done to check the competitive acceptability of the technique, considering the construction cost of the remediation plant and its daily operational and maintenance expenses. The results show that the proposed technique will be a competitive one for field applications for the remediation of soil contaminated with Cr(VI). The data and kinetic rate equation will be useful for the process design of the remediation of soil contaminated with Cr(VI).

Effect of As and MgO addition on arsenic vitrification in copper smelting slag

The arsenic (As) vitrification in copper smelting slag derived from the FeO−SiO2−Fe2O3−B2O3−CaO− Al2O3−(MgO) system was studied. The vitrification mechanism of As was systematically investigated by XRD, SEM, FTIR and XPS analysis. It is determined that As exhibits favorable compatibility with the iron-silicate slag. FTIR and XPS analysis indicates that As can partially substitute for silicon to form the Si—O—As structure, thereby enhancing the degree of polymerization of the melt. The [BO3]3− unit tends to decrease with the increase of the As content, while the opposite behavior is observed with the addition of MgO. Additionally, MgO increases the non-bridging oxygen (NBO) number of the melt. TCLP, SPLP and pH dependence tests show that the leaching toxicity of As increases with the increase of the As content but decreases with the addition of MgO. DSC analysis demonstrates that the incorporation of both As and MgO can improve the thermal stability of the As-containing glass.

Modified paddy husk carbon with linked fibrils of FeHO2 using aluminium as the surface regulator for enhanced As (III) removal in fixed bed system

Abstract The As (III) uptake capacity of Fe-impregnated AC greatly depends on the availability of active surface sites of iron oxide. In this context, utilizing aluminium as a surface regulator, we proposed a process to attach linked fibrils of FeHO2 to develop an adsorbent with enhanced As (III) adsorption capacity. The procedure was based on the hydrothermal process using paddy husk-based activated carbon, and both Iron and aluminium ions in the test hydrolysis solution. The exhaust time was observed to rise with increasing dose, falling flow rate, and influent concentration. The CCD optimization result showed that the FeAlPBC was an efficient and cost-effective adsorbent with a maximum response of 1681 min when the independent parameters were retained at 15.0 g FeAlPBC dose, 500 μg/L influent concentrations, 2.0 mL/min flow rate, and a desirability value of 0.986. The experimental results and Thomas and advection-diffusion models were in good agreement. The FeAlPBC samples can be recycled for four cycles with little to no reduction in adsorption capacity. Also, the TCLP test demonstrated that the used FeAlPBC were inert and could be put into landfills without risk. In conclusion, FeAlPBC is a strong contender for removing As (III) from potable water and has a wide range of potential future applications.

Fired brick production using phosphogypsum and phosphate mining waste

The main objective of this study is to propose advanced solutions for recycling phosphogypsum (PG) in the construction industry. In Morocco, PG has been produced in large quantities (around 20 million tons) by a series of phosphoric acid manufacturing plants for many years. To address this issue, fired bricks were created using PG and red clay (RC), a waste material from Moroccan phosphate mines. The pressed brick samples were dried at 105 °C and then fired at temperatures between 900 and 1100 °C for 2–5 h. The PG, RC, and sintered briquettes were characterized and analyzed through thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), physical properties and response surface methodology (RSM). The Toxicity characteristic leaching procedure test (TCLP) was also conducted on the raw materials and the fired brick samples to assess contamination risk. At all temperatures, the addition of PG results in a microstructure with high porosity that significantly impacts the mechanical characteristics. Despite this, the mechanical and physical performance of the fired brick samples meet the required standards. The TCLP test results did not detect any release of contaminants. The samples fired at 1056 °C for 4.5 h with a PG content of 40% demonstrate optimal conditions, exhibiting a notable bending strength of 13.15 MPa, a moderate density, and minimal water absorption. These findings indicate a promising and sustainable future trend in the construction industry by incorporating PG in fired brick production, providing a viable solution for waste management. Furthermore, comparing the results with previous works highlights the significant improvements achieved in terms of meeting industry standards and minimizing contamination risks associated with the utilization of mine wastes in fired bricks.

Effects of Basicity Index on Incinerator Fly Ash Melting Process and Stabilization

The generation of hazardous industrial waste in Taiwan has rapidly increased, reaching 1.5 million tons produced annually in 2021. Most of this waste was burned in incinerators, with about 15% (225,000 tons) of it converted into fly ash. Incinerator fly ash primarily consists of heavy metals, dioxins, chlorides, and silica. Historically, fly ash disposal has only relied on cement solidification, contributing to insufficient landfill capacity and soil-pollution concerns. To address these issues, the melting process has been a feasible solution, wherein the heavy metals can be encapsulated within a vitrified structure to prevent them from leaching out. However, the melting point of fly ash is too high, so this study aimed to explore the optimal basicity index for fly ash to conduct the melting process. Basicity indices are estimated by the ratio of CaO/SiO2, and the melting point of the fly ash can be decreased during the melting process with the right basicity index. In this study, the characteristics of incinerator fly ashes from industrial waste and laboratory waste were initially investigated. With their basicity indices adjusted with two sources of silica, the fly ashes were tested at 1100~1400 °C to observe whether they melted. The vitrified slags were subsequently subjected to TCLP, XRF, and ICP tests to verify their stability. In summary, we discovered that fly ash could be melted through the melting process with the basicity index adjusted to under 1.28, with the silica source as either glass or silica sand powder. After melting, the heavy metals were confirmed to be stabilized in the vitrified slags. Consequently, the melting process could be an alternative solution for fly ash disposal that is sustainable and eco-friendly.

Bioleaching of valuable metals from spent LIBs followed by selective recovery of manganese using the precipitation method: Metabolite maximization and process optimization

Despite the increased demand for resource recovery from spent lithium-ion batteries (LIBs), low Mn leaching efficiencies have hindered the development of this technology. A novel process was devised to enhance the dissolution of metals by producing citric acid using a molasses medium by Penicillium citrinum. This investigation used response surface methodology to investigate the influence of molasses concentration and media components on citric acid production, which demonstrated that molasses (18.5% w/w), KH2PO4 (3.8 g/L), MgSO4.7H2O (0.11 g/L), and methanol (1.2% (v/v)) were the optimum values leading to the production of 31.50 g/L citric acid. Afterward, optimum inhibitor concentrations (iodoacetic acid: 0.05 mM) were added to accumulate citric acid, resulting in maximum bio-production (40.12 g/L) of citric acid. The pulp density and leaching time effect on metals dissolution was investigated in enriched-citric acid spent medium. The suitable conditions were a pulp density of 70 g/L and a leaching duration of 6 days, which led to the highest dissolution of Mn (79%) and Li (90%). Based on the results of the TCLP tests, the bioleaching residue is non-hazardous, suitable for safe disposal, and does not pose an environmental threat. Moreover, nearly 98% of Mn was extracted from the bioleaching solution with oxalic acid at 1.2 M. XRD, and FE-SEM analyses were utilized for further bioleaching and precipitation mechanism analysis.

Performances of compressed stabilized bricks using phosphate waste rock for sustainable construction

Huge volumes of phosphate waste rock are generated during the extraction of sedimentary ores, and deposited around the mining site, covering large surfaces and causing many environmental problems. This study presents a cost-effective and environmentally friendly solution allowing the valorization of phosphate waste rock (PWR) to produce eco-friendly compressed stabilized earth bricks-CSEB. CSEB is one of the earthen building materials family, offering many advantages in terms of insulation and thermal properties, good mechanical performances, use of local raw materials, and low embodied energy… For the soil classification, PWR was first characterized using chemical, mineralogical, and geotechnical properties. Then, various mixtures were formulated at the laboratory scale using PWR with cement as a stabilizer and red marl employed to enhance the cohesion and brick’s consistency. The objective was to investigate the role of cement and red marls additions, curing conditions, and brick shapes on different CSEB properties. The optimal formulation that satisfied the requirements of the international standards was adapted to the pilot scale, using hollow and solid brick forms with a size of (250*125*75) mm3. The laboratory results showed that the use of 10% cement with 10% red marl seems to be the most adequate. The pilot scale findings revealed that the addition of cement and red marl improves the compressive strength that reaches 5.70 and 2.56 MPa, for hollow bricks in dry and wet states, respectively. For solid blocks, 4.51 and 2.44 MPa were obtained in both states, respectively. The obtained water absorption coefficients respect the requirements of the standards. The thermal conductivity values are acceptable; 0.44 and 0.51 W.m-1.K-1. The TCLP test of the elaborated bricks showed that the concentrations of leached contaminants (Pb, Cd, As, Cr) are below the requested limits.

Hydrogen production and pollutants emission characteristics by co-gasified of paper-mill sludge and automobile shredder residues in a commercial scale fluidized bed gasifier

This research investigated the hydrogen production and energy conversion from automobile shredder residues (ASRs) and paper mill sludge (PMS) co-gasified in a full-scale fluidized bed gasification plant. The results obtained from full-scale tests provided important information on the feasible assessment of ASRs-to-energy and the selection of alternative technologies for ASRs. Based on the analysis results of produced gas composition, H2, CO, and CH4 composition produced from paper-mill sludge gasified were 4.17%–6.01%, 3.08%–4.32%, 1.71%–2.4%, respectively. Another C2 gas composition ranged from 2.9% to 3.59%. The heating value of produced gas ranged between 1.64 MJ/Nm3 and 2.18 MJ/Nm3. In the case of 10% ASR addition, the heating value of produced gas was slightly increased to 1.84 MJ/Nm3-2.34 MJ/Nm3. The dioxin emission concentration of flue gas was approximately 0.064 ng I-TEQ/Nm3. It can comply with Taiwan regulation thresholds. The dioxin leaching concentrations of residues derived from gasification were also in compliance with regulation limits by the TCLP test. Meanwhile, in the case of 10% ASRs addition, the dioxin equivalence concentration of gasified residue was nearly 0.002 ng I-TEQ/Nm3. It was far below the current regulation standard limit. In summary, the results of this research have proved the performance of ASRs-to-energy by co-gasified with paper mill sludge using a full-scale gasification plant. The results obtained from this research also provided the information for selecting ASRs alternative technologies and operating full-scale gasifiers in the future.

Study on phase evolution and promoting the pozzolanic activity of electrolytic manganese residue during calcination

Electrolytic manganese residue (EMR) is a harmful by-product in the electrolytic manganese industry. Calcination is an efficient method for disposing EMR. In this study, thermogravimetric-mass spectrometry (TG-MS) combined with X-ray diffraction (XRD) was used for analysing the thermal reactions and phase transitions during calcination. The pozzolanic activity of calcined EMR was determined by the potential hydraulicity test and strength activity index (SAI) test. The leaching characteristics of Mn were determined by TCLP test and BCR SE method. The results showed that MnSO4 was converted into stable MnO2 during calcination. Meanwhile, Mn-rich bustamite (Ca0.228Mn0.772SiO3) was converted into Ca(Mn, Ca)Si2O6. The gypsum was transformed into anhydrite and then decomposed into CaO and SO2. Additionally, the organic pollutants and ammonia were completely removed following calcination at 700 °C. The leaching concentration of Mn decreased from 819.9 mg L−1 to 339.6 mg L−1 following calcination at 1100 °C. The chemical forms of Mn were transformed from acid-soluble fraction to residual fraction. The pozzolanic activity tests indicated that EMR1100-Gy maintained a complete shape. The compressive strength of EMR1100-PO reached 33.83 MPa. Finally, the leaching concentrations of heavy metals met the standard limits. This study provides a better understanding for the treatment and utilization of EMR.

Analysis Of Hazardous Medical Waste In Dr. Soehadi Prijonegoro Hospital Using A Life Cycle Assessment Approach

Hospitals are health services that produce waste and sources of pollution for human health and the environment. dr. Soehadi Prijonegoro Hospital produces the most medical waste in the sragen regency and still needs cold storage. This research evaluated the management of hazardous toxicity material medical, solid waste. Life cycle assessment calculations can be performed using a software application, simparo 9.0. This scope of research with gate to gate approach. Inventory data was obtained from primary and secondary data collection. Daily medical waste is about 135 kg, while the average month is 3961 kg—medical waste management in dr. Soehadi Prijonegoro includes reducing, sorting, labeling, storage, transporting, and processing have been following applicable regulations. The results of the TCLP test of solids incinerator ash and chimney incinerator emissions meet the quality standards. The most significant impact on the ecosystem is the global warming potential in the emergency service room. For impacts, the natural resources and the impact on the ecosystem is the inpatient room due to excessive use of medical waste. Use of energy and materials to minimize emissions and waste. Keywords: Hospital, Waste, Impact

Utilization of textile and tannery sludges in cement mortar

The aim of this study is to investigate the characteristics of Textile ETP and Tannery sludges and strength characteristics of cement-sludge mortar. The textile Effluent Treatment Plant (ETP) and tannery sludges have the potential to become a serious environmental burden for Bangladesh in the future because of their high rate of generation, with a very limited safe disposal option. On the other hand, day by day the demand and price of cement are increasing. This study was devoted to evaluate the technical feasibility of utilizing textile ETP and tannery sludges in cement mortar both as separate and mixed modes. An attempt was taken to replace 5%, 10%, 15% and 20% by weight of cement in mortar with textile ETP and tannery sludges both as a separate and mixed modes. To evaluate the characteristics of the textile ETP and tannery sludges, the pH, moisture content, organic matter content, chemical composition (XRF), TCLP (Heavy Metal) tests were studied. The initial and final setting time, compressive strength, tensile strength, and water absorption of mortar by partial replacement of cement by textile ETP and tannery sludges both as separate and mixed modes were studied to evaluate the properties of cement-sludge mortar. It was found that the textile ETP and tannery sludges both as separate and mixed modes can be a replacement of cement up to 10% in cement mortar and can be used for the purposes of S-type of mortar. The textile ETP sludge as a separate and mixed modes of the sludges can be a replacement of cement up to 20% and can be used for the purposes of N-type of mortar.

Utilization of Sandblasting Waste as an Alternative Material for Paving Blocks

Sandblasting is an activity of cleaning industrial equipment made of metal using quartz sand. Every day the amount of waste produced is getting bigger so it needs to be processed to reduce its surface area. One way that can be used to process sandblasting waste is solidification into building material products. This study uses sandblasting waste as a substitute for fine aggregate in the manufacture of paving blocks. Paving block production was carried out using three research variables, namely the weight ratio of cement and waste, cement water factor (FAS), and maximum grain size. Comparison of the weight of cement and waste using composition of 1:3, 1:4, and 1:5. The cement water factor used was 0.35, 0.425, and 0.5. While the grain sizes that were filtered were 1.2 mm, 2.4 mm, and 4.75 mm. The results showed that of the 27 variations of the mixture produced, the samples with sample code V5 (composition 1:3, FAS 0.425, and grain size 2.4 mm) produced the highest compressive strength, namely 25 MPa with quality B. ANOVA analysis was performed to determine the effect of the three variables on compressive strength and it was found that the weight ratio composition of cement and waste was the most influential. The TCLP test was carried out to determine the potential for leaching of heavy metals Cr6+, Cu, Pb, and Zn, which then resulted in the content of the four substances being below the quality standard of Government Regulation Number 22 of 2021

Elaboration of compressed earth blocks based on phosphogypsum and phosphate mining by-products

The present paper aims to propose new recycling solutions to maximize the use of phosphogypsum (PG) in construction applications. The performance of several formulations for the manufacture of cement-stabilized compressed earth bricks (CEBs) made of raw PG mixed with phosphate mining waste rocks (Calcareous material (CM) and red clay (RC)) was investigated. The main roles of CM and RC are respectively to neutralize the acidity generated by the PG and improve the consistency of CEBs. This research work started at a laboratory scale to optimize and find the best formulation that will satisfy national and international standards. The optimized mixtures were scaled up through pilot experiments using two brick shapes (solid and hollowed). The impact of the brick shape elaborated in the pilot scale was also examined. The mineralogical, environmental, and geotechnical characteristics of the raw materials were also studied. The toxicity characteristic leaching test (TCLP) was performed on the raw PG and also on the ground bricks to investigate the risk of contamination. The most optimized laboratory mixture involved 40% PG and only 8% of ordinary Portland cement. This mixture allowed to reach an unconfined compressive strength after 28 days around 8.1 and 7.7 MPa at laboratory and pilot scale respectively. The thermal conductivity of the developed CEBs was interesting; between 0.484 and 0.506 W m−1 K−1. The values of bulk density and water absorption coefficient by capillarity are in accordance with the requirements indicated by the standards. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses highlighted the formation of tobermorite (5CaO·6SiO2,2H2O) and ettringite (Ca6Al2(SO4)3(OH)12,26H2O). The TCLP test of PG used and optimized bricks in this study showed no contaminant release. The obtained results are very promising; they showed that the elaborated CEBs can be adapted to compressed earth blocks applications.

Historical Lead Smelting Slag Harmlessness and Valuable Metals Recovery: A Co-Treatment of Lead Slag and Zinc-Bearing Material in Rotary Kiln

The harmless treatment of historical lead smelting slag (LSS) is of significance to ecological and environmental protection, but it is still challenging in terms of the economic feasibility of alone processing due to the low content of valuable metals. Here, we performed an industrialized test with a co-treatment of LSS and zinc oxide ore in a rotary kiln to evaluate the economic feasibility and solidification effect of harmful elements. The results revealed that more than 70% of Zn and Pb were recovered from LSS in the form of dust, while the nonvolatile part of Pb, Zn, and Cd were solidified in gangue as complex silicate phases. The nonvolatile part of As came into being Fe-As intermetallic compound which was encapsulated by gangue particles or was solidified in silicate phases. The entirely enclosed structure of water-quenched slag plays an important role in the stability of slag. The TCLP and SNAL leaching tests demonstrated the high stability of water-quenched slag. A zinc oxide ore addition of 20% was recommended for energy consumption and processing capacity. Our findings highlight that the valuable metals not only can be effectively recovered but also harmful elements are solidified in gangue, providing an economical and feasible technical route for the treatment of historical LSS.

Highly effective remediation of high arsenic-bearing wastewater using aluminum-containing waste residue

Wastewater from non-ferrous metal smelting is known as one of the most dangerous sources of arsenic (As) due to its high acidity and high arsenic content. Herein, we propose a new environmental protection process for the efficient purification and removal of arsenic from wastewater by the formation of an AlAsO4@silicate core-shell structure based on the characteristics of aluminum-containing waste residue (AWR). At room temperature, the investigation with AWR almost achieved 100% As removal efficiency from wastewater, reducing the arsenic concentration from 5500 mg/L to 52 μg/L. With Al/As molar ratio of 3.5, the structural properties of AWR provided good adsorption sites for arsenic adsorption, leading to the formation of arsenate and insoluble aluminum arsenate with As. As-containing AWR silicate shells were produced under alkaline conditions, resulting in an arsenic leaching concentration of 1.32 mg/L in the TCLP test. AWR, as an efficient As removal and fixation agent, shows great potential in the treatment of copper smelting wastewater, and is expected to achieve large-scale industrial As removal.

Solidification/Stabilization of waste containing lead using flyash and bentonite

In this study, the Stabilization/Solidification was used to treat Pb as heavy metal waste using flyash and bentonite, as binder and mixing agent. Flyash and bentonite was mixed with the waste containing Pb and formed to cube called “mortar” with a size of 5x5x5 cm. The variations of flyash and bentonite were 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, and 0:100. Then the mortars had a curing time process for 7 days, 14 days, and 28 days. After curing time process, the products tested using a compressive strength test and TCLP test. Result of compressive strength test indicated that the optimum compressive strength value occurred in 100% fly ash composition with 28 days curing time. The estimation of compressive strength test was 3220 tons/m2. The result of the TCLP test showed the optimum TCLP test results occurred at 100% fly ash composition and the rate was 0,0338 mg/L Pb. The composition of fly ash and bentonite showed a significant effect on the compressive strength and TCLP test.