Metal Leaching Tests Research Articles

Gypsum-Enhanced Red Mud Composites: A Study on Strength, Durability, and Leaching Characteristics

The strong alkalinity of red mud and the heavy metals it contains pose a serious threat to the environment. This study investigated the possibility of applying red mud as a solid waste material in road construction to mitigate the problem of red mud accumulation. Red mud was modified using titanium gypsum and phosphogypsum as curing agents. The effects of varying gypsum types and mixing ratios on the mechanical properties and heavy metal leaching of the resulting red mud-based materials were assessed using percussion tests, unconfined compressive strength measurements, scanning electron microscopy (SEM), and continuous heavy metal leaching tests. The results showed that the optimal moisture content for titanium gypsum–cement-stabilized red mud (RTC) exceeds that of phosphogypsum–cement-stabilized red mud (RPC), with RTC exhibiting a lower maximum dry density compared to RPC. When the gypsum admixture was within 10%, the strength of the RPC was higher than that of the RTC at the same and curing time. The reticulation in RPC-10 was denser. The cumulative heavy metal releases from both RTC and RPC were within the permissible limits for Class III groundwater discharge standards. Based on the comprehensive test results, RPC is identified as the superior modified red mud material, with an optimal mix ratio of red mud/phosphogypsum/cement of 87:5:8.

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.

Study on the hydration characteristics of steel slag cement

The direct use of stainless steel slag in cement presents potential weaknesses in terms of strength and the risk of cracking, which limits its large-scale utilization. Therefore, it was crucial to explore the use of stainless steel slag in clinker cement. In this study, the hydration characteristics of stainless steel slag cement (SS) and ordinary Portland cement (OPC) were compared and analyzed using isothermal calorimetry, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM), and heavy metal leaching tests. The study investigated the hydration heat, compressive strength at curing ages of 1d, 3d, 5d, 7d, and 28d, hydration products, and safety aspects of SS and OPC. Results showed that the optimum calcination temperature of stainless steel slag cement (SC) and Portland cement (PC) are 1350℃ and the holding time is 2 h. The clinker composition of the two is similar. The main minerals are dicalcium silicate (C2S), tricalcium silicate (C3S), tricalcium aluminate (C3A) and aluminum ferrite tetracalcium (C4AF). Compared with OPC, SS shows a delayed heat release peak during hydration. SS exhibited a delayed exothermic peak in the heat release during hydration compared to OPC. Furthermore, during the stable hydration period, SS produced more calcium aluminate-type solid solution, tightly encapsulating the crystal surface, and exhibited lower heat release. With an increase in curing age, the contents of acicular ettringite (AFt), C-S-H gel, and hexagonal calcium hydroxide (CH) gradually increased in both SS and OPC. Due to higher contents of C4AF, C3S, and C2S in SS, it produced more AFt and C-S-H than OPC. The compressive strength of both SS and OPC increased with curing age, reaching 55.4 MPa and 42.4 MPa at 28 days, meeting the requirements of the national standard (GB/T 21372-2008) in terms of initial and final setting times and f-CaO content. Additionally, heavy metal leaching and soluble Cr6+ tests indicated that their use is safe.

MSWIFA and cement cooperate in the disposal of soft soil - experimental study on silty sand and silty clay.

Municipal solid waste incineration fly ash (MSWIFA) can be reused as a positive additive to strengthen soft soil. In this study, MSWIFA was initially used as a supplementary solidification material in combination with ordinary Portland cement to prepare fly ash cement-stabilized soil (FACS) with silty sand and silty clay, respectively. The ratio of MWSIFA to total mass was 5%, 10%, and 15%, and the cement content was set as 10% and 15%. The mechanical properties of FACS were evaluated by unconfined compressive strength test. The heavy metal-leaching test was conducted to estimate the environmental risk of FACS. The scanning electron microscope was used to test the micro-structure of FACS. The X-ray diffraction was performed to analyze material composition of FACS. The result indicates that the collaborative solidification of soft soil with MSWIFA and cement is feasible. Regarding the silty clay, the FA had positive effects on the silty clay in the service age (between 50 and 100% with 15% MSWIFA), as the MSWIFA reformulated the initial silty clay structure, resulting in interconnection and pore fill between particles. It can be founded that C-S-H and ettringite are the main products of MSWIFA and cement hydration, which are formed by the hydration of C3S and C2S. Regarding the silty sand, the MSWIFA decreased the peak strength (between 35 and 48% with 15% MSWIFA) but increased the ductility of the stabilized cement. Under the same mix proportions, the leaching toxicities of Zn and Pb in FACS of silty clay were obviously lower than were those of silty sand. Generally, the leaching concentrations of tested metals under all the mix proportions were well below the limit value set by GB 18598-2019 for hazardous waste landfill. Thus, the reuse of MSWIFA in cement-stabilized soil would be one of the effective methods in soft soil treatment and solid waste reduction.

Resistance and durability of fly ash based geopolymer for heavy metal immobilization: properties and mechanism.

Geopolymer technology is an effective method of fly ash (FA) disposal developed in recent decades. This study provided a novel technology based on geopolymerization for FA resource, which could solve the problem of long-term heavy metal leakage trends. Firstly, Unconfine compressive strength (UCS) of geopolymer and the heavy metals leaching test was taken to discuss the effects of oxidize species. The results indicated that the UCS of geopolymer samples was increased with the increase of CaO, and the largest 28 d UCS was 24.8 MPa when CaO content was 31.5%. When the CaO content was 32%, the leaching concentration of heavy metals was the lowest (Pb2+ was 0.02 mg L-1, Cd2+ was 0.01 mg L-1), and the solidification rate of heavy metal ions were more than 93.6%. Secondly, two methods were used to evaluate the corrosion resistance of FA based geopolymer. The observations suggested that the FA based geopolymer exhibits a high level of resistance to erosion caused by sulfate ions and chloride ions. Thirdly, carbonation tests were taken to discuss the durability of FA based geopolymer. The results shown that UCS exhibited a modest rise following the process of carbonation, and then demonstrated a stable trend after a period of 28 days, and the heavy metal leaching test results that comply with the limitations specified in the national standard at 7, 14, 28, and 56 days. The findings from accelerated carbonization tests at 56 days, determined by empirical equations, suggest that the carbonization age of geopolymers is projected to be 102 years. Finally, XRD, FTIR and SEM were taken to discuss the microstructure characterization of FA based geopolymer, and solidification mechanisms of heavy metal ions by geopolymer materials could be concluded as gelation, physical encapsulation, and chemical reactions.

Effect of industrial sludge particle size on the performance of baking-free sludge bricks

ABSTRACT Cement solidification is essential to reduce heavy metal leaching from industrial sludge and make it recyclable. This paper studied the effect of aggregate grading optimized by sludge containing heavy metal of different particle sizes on the performance of baking-free sludge bricks, which was mixed with industrial sludge cured by both micro-silica fume and cement. First, the gradation of fine natural aggregates was adjusted according to the Fuller curve. Fine aggregates in baking-free bricks were replaced by artificially processed sludge with particle sizes of 0.15 mm ~0.3 mm and 2.36 mm ~4.75 mm. In this case, a mixed proportion scheme was designed. Then, the strength, water absorption, porosity, and heavy metal leaching were measured. With the help of nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM), the phase and pore structures were observed. The test results showed that: (1) Sludge can replace part of the fine aggregates to make baking-free bricks, resulting in the reduction of the strength of baking-free bricks, but the strength still meets the standard strength requirements of GB/T 21,144-2007. (2) When fine aggregates are partly replaced by sludge with finer particle sizes, baking-free sludge bricks exhibit higher strength, lower water absorption, better pore structures and microphase structure, and stronger solidification of heavy metals, the leaching number of heavy metals meets the standard requirements of GB5085.3–2007, which will be provided support for actual industrial production. Implications: Cement solidification is an essential means to reduce the heavy metal leaching from industrial sludge and make it recyclable. This paper studied sludge containing heavy metal of different particle sizes on the performance of baking-free sludge bricks. This paper analyzed the compressive strength, porosity and water absorption of baking-free bricks mixed with sludge of different partical sizes, and adopted the NMR to characterize the pores of baking-free bricks, and the SEM to observe the baking-free bricks resultants and the interfacial transition zone (ITZ). The heavy metal leaching test verified the environmental benefits of baking-free bricks mixed with sludge instead of aggregates. There not only make full use of solid wastes, but also thus minimizing pollution to the environment, which provide support for actual industrial production and a reference for studying industrial sludge recycling technology.

Resource utilization of ultrasonic carbonated MSWI fly ash as cement aggregates: Compressive strength, heavy metal immobilization, and environmental-economic analysis

Ultrasonic carbonation technology is effective for municipal solid waste incineration fly ash (MSWI FA) pretreatment. However, the subsequent disposal route is unclear. In this study, the mechanical strength and heavy metal immobilization effects of raw FA (RFA), washed FA (WFA), conventional carbonated FA (CFA), and ultrasonic carbonated FA (UFA) as cement aggregates in the preparation of concrete were investigated in comparison. The reaction kinetic analysis showed that ultrasonic excitation promoted the internal diffusion phase of the carbonation reaction. The compressive strength of the 28-day solidified bodies was in the order of UFA (32.2 MPa) > CFA (22.8 MPa) > WFA (16.4 MPa) > RFA (12.6 MPa). The 3-day UFA solidified body showed the highest degree of hydration and polymerization through 29Si solid-nuclear-magnetic analysis. The nano-CaCO3 in the UFA provided more nucleation sites and hydration reaction sites for the hydration reaction. In addition, the fine UFA particles filled the pores between cement particles, enhancing the strength of the product. Heavy metal leaching tests described that CFA and UFA met the criteria for resource utilization (HJ/T 1134–2020), and the immobilization efficiency of Cu, Pb, and Zn in the UFA solidified body was above 95.6%, 99.3%, and 99.2%, respectively, mainly by the dual immobilization of carbonate chemical precipitation and cement hydration. Considering 11 environmental impact factors and economic benefits, life-cycle-assessment and cost-benefit analysis were selected. The integrated environmental-economic results show that cement usage is the main influencing factor. UFA scenario was recommended as engineering applications with low global warming potential.

Basic properties, characteristic heavy metals leaching and migration of coal incineration fly ash-based mortar

Accumulation of fly ash causes waste of land resources and certain environmental pollution problems, mainly from coal incineration. As a result, to investigate the leaching, migration law, and environmental safety of these distinctive heavy metals, this study used representative fly ashes from two power plants as research objects to screen out the characteristic heavy metals and prepare and test mortar specimens. The results of the study show that after four heavy metal risk assessment methods, it was concluded that the characteristic heavy metals where are in A power plant’s fly ash were Hg, Cr, Pb and As, and in that of power plant B were Hg and As. The best fly ash admixture was 20% and the best water-binder ratio was 0.48, as learned from the compressive strength experiment. The heavy metal leaching test was done for block mortar and crushed mortar on the use of the best mix ratio. When compared to the raw materials, the specimens' heavy metal leaching content was significantly lower. And the heavy metals in crushed mortar were easier to leach. After the analysis of the migration transformation model, the heavy metals migrated downward in the mortar under the action of gravity. According to the one-dimensional diffusion model of Fick's second law, the migration of the various characteristic heavy metals was ranked from strong to weak as Pb, As, Cr, and Hg, and the ranking of the maximum safe age was ranged from large to small as Hg, Pb, Cr, and As. The findings of the study will provide fundamental theoretical support for the environmental safety risk posed by heavy metals and safety controls like the leaching of characteristic heavy metals in current fly ash-based mortar products. They will also provide further guidance on how to use fly ash as a resource.

Resistance to Sulfate Attack Under Drying–wetting Cycles of Reactive Magnesia–microbial Cured Electrolytic Manganese Residue

The reactive MgO (r-MgO)-microbial curing technology can not only effectively improve the strength of electrolytic manganese residue (EMR) but also repair heavy metal ions. By conducting unconfined compressive strength (UCS) test, heavy metal leaching test, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), the effects of the type and concentration of sulfate on the strength and repair of heavy metals of the cured EMR under drying–wetting (DW) cycles were studied, and the strength and the evolution mechanism of heavy metal remediation is elucidated. The results indicate the following: With the increase in the number of DW cycles, the dry density of the samples in high concentration of MgSO4 first increased slightly and then decreased gradually and became stable. The dry density of the samples in Na2SO4, low concentration of MgSO4, and water generally showed a downward trend. The pH of the soaking solution slightly decreased, and the leaching concentration of heavy metal Mn2+ ions always remained at a low level. The UCS of the samples in MgSO4 first increased slightly and then decreased gradually, and then became stable. The amount of cured products first increased and then decreased, and the size of internal pores first decreased and then increased. The UCS of the samples in Na2SO4 and water gradually decreased and became stable. The amount of cured products gradually decreased, and the size of internal pores gradually increased. The research results provide a theoretical basis for the evaluation of resistance against the sulfate corrosion of cured EMR under DW cycles.

Preparation and characterization of mortar specimens based on municipal solid waste incineration fly ash-activated slag

Municipal solid waste incineration fly ash (MSWIFA) contains a large amount of heavy metals, inhibiting resource utilization. This study used MSWIFA as an alkali activator and ground-granulated blast-furnace slag (GGBS) as a precursor to prepare the MSWIFA GGBS binder. Based on this, used the iron tailing sand instead of natural river sand as fine aggregate prepared mortar specimens by cooperative compression molding. Compressive strength, bulk density, water absorption, and heavy metal leaching tests were conducted and combined with micro XRD, FTIR, and SEM examinations to characterize the mortar specimens. The results show that the optimal MSWIFA: GGBS was 2:8. It was also found that increasing the molding pressure was beneficial to strength development. Compared to the specimens without the application of molding pressure, the 3 d and 28 d strength values increased by 148.6 and 122.2%, respectively, after the application of 35 MPa molding pressure. The reason is that the pressure effect can increase the cohesion of the particles, promote the hydration reaction to proceed, and the hydration products increase to fill the pores, increase the structural compactness and promote strength development. The resource utilization of MSWIFA must be guaranteed not to produce environmental pollution simultaneously. For this reason, the heavy metal leaching test was conducted on 28 d mortar specimens, and the results showed that the leaching rates of Zn, Pb, Cu, Cr, and Ni met the requirements of the Chinese Standard (GB16889-2008). The research results can provide a theoretical basis for the large-scale recycling of MSWIFA.

Solidification Experiment of Lithium-Slag and Fine-Tailings Based Geopolymers

Based on the pressure of environmental protection, more and more scientific researchers are trying to reuse aluminum–silicon-rich industrial wastes. In this study, activated lithium-slag and lead–zinc tailings were used as raw materials to prepare geopolymers at ratios of 3:7, 1:1, and 7:3. These geopolymers were initially cured for 12 h at 25 °C, 50 °C, 75 °C, and 100 °C and were then cured at room temperature to the specified ages. The compressive strength of each group of geopolymers was tested at the ages of 3 days, 7 days, and 28 days. The optimal group of samples was selected, that is, those with a ratio of lithium-slag to lead–zinc tailings of 7:3 and an initial curing temperature of 75 °C. After that, the heavy metal leaching test and porosity analysis test were carried out on the optimal group of samples, and the curing effect was considered to meet the requirements of the Chinese specifications. In addition, in order to reveal the mechanism of the chemical reaction, scanning electron microscopy and X-ray diffraction (XRD) were used to study the microstructure and hydration products of the C3 group cured samples. This study provides a new concept for the reuse of industrial wastes such as lithium-slag and fine-tailings.

Synergistically enhanced activation of peroxymonosulfate by Fe3O4@ZSM-5 catalysts for ciprofloxacin degradation: Performance, kinetics and mechanism insight

Exploring an environmentally friendly and highly activation catalysts in the advanced oxidation processes (AOPs) basing on sulfate radicals (SO4−•) has shown great importance for the remediation of refractory contaminants. Herein, Fe3O4-wrapped ZSM-5 (Fe3O4@ZSM-5) was constructed as heterogeneous catalyst to remove ciprofloxacin (CIP) via peroxymonosulfate (PMS) activation, in which performance, kinetics and mechanism insight were investigated in depth. The removal efficiency of CIP reached 90 % by Fe3O4@ZSM-5 catalysts within 100 min reaction when the initial pH was 3.0. During the reaction, SO4−• and HO• were proved to be coexisted in reaction system and SO4−• played a critical role in CIP degradation according to the radical quenching experiments and electron paramagnetic resonance (EPR) measurements. Based on the catalyst characterization and Langmuir-Hinshelwood adsorption kinetics analysis, the synthesis of Fe3O4 nanoparticles (NPs) and ZSM-5 accelerated the dispersion process and enhanced adsorption ability of Fe3O4 NPs, which further promoted the local concentration of CIP and PMS on the surface. In addition, the cycling experiments and metal leaching tests demonstrated that Fe3O4@ZSM-5 catalysts were stable and could be conveniently reused by magnetic separation. In addition, the impacts of coexisting irons (Cl−, SO42−, NO3−, HCO3−) confirmed that Fe3O4@ZSM-5 was still effective in real water. This study demonstrated the promising prospect of Fe3O4@ZSM-5/PMS system in the application of degradation refractory organic pollutants.

Metal leaching test of commercially available faucets in the Japanese market in 2016-2020.

In this study, metal leaching was investigated in commercially available faucets in Japan to clarify their compliance to Japanese regulations. We purchased 37 faucets from the market and analyzed the leaching of cadmium, mercury, selenium, lead (Pb), arsenic, hexavalent chromium, boron, zinc (Zn), copper, manganese, and nickel. The leaching tests were performed with and without a conditioning treatment, that simulated approximately 1-month intermittent use of faucets on weekdays, and the results were compared to estimate the changes in metal leaching during the use of faucets. The results revealed that metal leaching from most of the faucets complied with Japanese regulations. However, the levels of Pb leaching from several faucets produced by certain manufacturers exceeded the Japanese standard. The conditioning treatment was generally effective in reducing metal leaching. However, the reductions in Pb and Zn leaching tended to be lower than those of the other metals. Nickel is not legally regulated in Japan; although the number of cases where nickel concentration in leachate exceeded the water quality management target value was greater, such cases were limited to faucets primarily made of copper alloys. We believe that these results will be helpful to improve the public health associated with metal leaching from faucets.

Magnetic Fe3S4/MoS2 with visible-light response as an efficient photo-Fenton-like catalyst: Validation in degrading tetracycline hydrochloride under mild pH conditions

Magnetic Fe3S4/MoS2 composites with a visible light response were prepared, and their degradation activity was tested using tetracycline hydrochloride (TCH) as a simulated pollutant. The mass ratios of Fe3S4 and MoS2, pH change, temperature, H2O2 concentration, and catalyst addition were investigated to determine the mechanism of TCH degradation. The results show that the removal rate of TCH by the Fe3S4/MoS2 composites is much higher than that of the pure Fe3S4 or MoS2 under pH values ranging from 1.2 to 13.2. The removal rate of TCH by Fe3S4/MoS2 was 376.37 and 5.45 times higher than that of pure Fe3S4 and MoS2 when the mass ratio of Fe3S4 and MoS2 was 1:1 at pH 7.2. The main free radicals and metal leaching changes are analyzed. The removal mechanism of TCH was proposed by the free radical scavenger test and the metal leaching test. The mechanism proposed in this paper shows that the high catalytic activity of Fe3S4/MoS2 composite is due to the acidic microenvironment near the surface of the composite, which reduces the production of ferric hydroxide sludge.

Design and Manufacturing of Bottle Roller Machine for Laboratory Leaching Process by Using Recycled Materials

Bottle roll is the equipment used for laboratory metal leaching tests. Leaching is a widely used metal extraction process by dissolving metal from ore using certain chemical reagents. The working principle of the bottle roll is to stir the bottle filled with a suspension sample and place it on rolls that rotate horizontally. In this research, the rotating rolls were driven by a recycled water pump electric motor which is transmitted using a pulley and belt. The research objective is to create a bottle roll machine that is practically easy and safe to carry out the leaching test or any other tests that involve agitation, especially for process engineering students. The performance validation of the equipment was done by conducting some leaching tests using the manufactured bottle roll to determine the consistency of the roll rotation, as leaching tests are generally done for a quite long period, usually 24 hours continuously. The sand sample was sieved into 100 mesh of particle size and then mixed with water to make a suspension. The suspensions were put into 2.5 liters of used glass chemical bottles and 1 liter HDPE plastic bottles with various diameters of 14 Cm, 12 Cm, and 8 Cm. The results showed that the machine could perform the leaching test at best in HDPE bottles with an average of 31 RPM of rotation speed tested for 24 hours.

MOF-Derived Cu@N-C Catalyst for 1,3-Dipolar Cycloaddition Reaction.

Cu(im)2-derived Cu@N-C composites were used for the first time as efficient heterogeneous catalysts for one-pot 1,3-dipolar cycloaddition of terminal alkynes, aryl halides, and sodium azide to preparation of 1,4-disubstituted 1,2,3-triazoles with broad substrate scope and high yields. The catalyst can be easily reused without the changes of structure and morphology, and the heterogeneity nature was confirmed from the catalyst recyclability and metal leaching test.

Magnetic Fe3O4/CeO2/g-C3N4 composites with a visible-light response as a high efficiency Fenton photocatalyst to synergistically degrade tetracycline

Magnetic Fe3O4/CeO2/g-C3N4 (FCG) composites with a visible-light response were successfully synthesized and characterized as a heterogeneous Fenton-like catalyst for tetracycline hydrochloride (TCH) degradation. The optimal mass ratio, pH value, catalyst addition, H2O2 concentration, and temperature were explored. Photodegradation studies showed the best activity when the mass ratio of the composite was 1:0.75:0.75 (F1C0.75G0.75) and the removal rate of TCH by F1C0.75G0.75 reached 96.63% after 180 min. The first order kinetic constant of the reaction system was 0.0533 min−1. According to the test of free radical scavenger and metal leaching tests, the Fenton-like degradation of TCH by F1C0.75G0.75 composite was analyzed. g-C3N4 effectively reduced the leaching of Fe and the location where TCH was attacked by hydroxyl radicals was mainly on the surface of the catalyst. The reusability of the F1C0.75G0.75 composites was also studied after five cycles.

In Situ Generation of Hydrogen Peroxide Using Polymetallic-Doped g-C3N4 for Pollutant Removal

Fenton reaction is a powerful technology for pollutants’ removal from water. However, the cost of H2O2 becomes one of the major stumbling blocks in its application. H2O2 has a relatively high price and is easily decomposed during transportation and use; therefore, in situ synthesis of H2O2 could improve economic benefits effectively. In this study, a Fe/Ni/Pd ternary metal-doped graphitic carbon nitride (FeNi-Pd@CN) is prepared, and in situ H2O2 generation using formic acid as hydrogen sources for organics removal was proved. The catalyst is advantageous, as H2O2 could accumulate to 1.69 mmol/L in 150 min when pumping air rather than oxygen gases in other studies. Furthermore, 92.0% of Acid Red 73 (200 mg/L) and 93.2% of tetracycline hydrochloride (10 mg/L) could be removed in 150 min without any pH adjustment. Characterization results show that the catalyst has good stability in metal leaching and reuse tests. It is proved that •OH and •O2− are the main reactive oxygen species, and a synergistic effect between Fe and Ni exists that enhances ROS generation for organics degradation. This work offers a promising method to remove refectory organic contaminants from industrial wastewater.

Development of Reinforcement Grout Materials Based on Blast Furnace Slag according to the Content of Reinforcement Fiber

The grouting is used to reinforce soft ground and to prevent the leakage of water in the soil. The objective of the study is to enhance the compressive strength of grout materials by using reinforcing fibers and to increase the strength of soil using blast furnace slag powder. For this purpose, cement was replaced with the blast furnace slag powder by 30 to 60%. Furthermore, for comparison of carbon fibers with aramid fibers, each fiber was added by 0, 0.5, and 1.0% of the weight of material. As the contents of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased. This is due to the interlocking of fibers in the grout material that increased the uniaxial compressive strength. Moreover, the grout material reinforced with aramid fibers showed an increase of uniaxial compressive strength by at least 20% compared to the carbon fibers. An environmental assessment was done through a heavy metal leaching test and a pH test. The test result reveals that about 50% of chromium (VI) leaching decreased as 30% more blast furnace slag powder was used but the pH test shows about 0.5 pH increased as 30% more blast furnace slag powder was used. Further study is necessary for the pH test.

Regeneration of heavy metal contaminated soils for cement production by cement kiln co-processing

Co-processing is considered as an effective way to reduce the cost and environmental footprints for cement production by replacing fuel or raw materials with wastes. In this study, we investigated the influences of co-processing of heavy metal-contaminated soil in cement kiln on the engineering integrity and heavy metal leachability of cement powders and cement mortars. The replacements of the contaminated soil were set at 0, 3.0, 7.6, and 10.0 wt.%. Engineering integrity of the cement products was verified first using typical performance tests, followed by three heavy metal leaching tests, namely Toxicity Characteristic Leaching Procedure (TCLP), EDTA-mediated TCLP and Synthetic Precipitation Leaching Procedure (SPLP). The results showed that in TCLP, only Cr was the concern, in which leachates of cement powders produced by co-processing with > 7.6% soils exceeded the TCLP Cr limit (5.0 mg/L), whereas all leachates of cement mortars met the regulations. EDTA-mediated TCLP could potentially release higher Cr concentrations, indicating that cautions were still needed when applying the cement products in harsh environments. Preliminary economic assessment indicated that using co-processing to treat heavy metal-contaminated soils can bring benefits for both cement industry and soil polluter. Overall, cement kiln co-processing could be an attractive alternative for the remediation of heavy metal-contaminated soil to revive the contaminated site and reduce the environmental impacts of cement production.