Journal of Hazardous, Toxic, and Radioactive Waste

Red mud (RM) is a by-product in the alumina manufacturing process, which is generated in large quantities. The challenge of increasing RM reserves poses a threat to the environment and can be addressed by its utilization in the construction industry. This study presents a comprehensive review of RM's effect on the various properties of cementitious and noncementitious materials to understand the feasibility of employing it to produce sustainable construction materials. The various studies reviewed suggest that RM could successfully be incorporated in concrete, mortar, bricks, and ceramic materials and can be used as a potential replacement for different property-enhancing admixtures. Besides that, the use of RM combined with other industrial by-products could further enhance efficient resource consumption. The article addresses the incorporation of RM as a partial replacement of cement, fly ash, and filler materials, appraising its influence on the fresh, hardened, durability, and radiological properties of the materials. The results revealed that RM with high pozzolanic activity could be used at low replacement levels to enhance the mechanical properties of the other materials. However, RM usage could improve the durability properties even for higher replacement levels. Considering the strength and environmental performance, conservatively RM can be around 50% as fly ash replacement and 12.5% as cement replacement in concrete mixes. It can be used at 40% as fly ash replacement and 20% as cement replacement for mortar mixes. Since RM's characteristic properties vary significantly based on its source, the extent of its incorporation must be decided based on the required application and properties for effective usage. Utilization of RM in the construction, as mentioned, can address waste reduction, one of the primary aspects of the aluminum industry's cleaner production.

The unchecked emissions of hazardous gases emanating from the cement industry have effectuated much research geared toward utilizing solid waste materials as cement replacements. This study addressed the incorporation of ceramic waste (CW) from the ceramic industry, as well as construction and demolition waste materials, as cement replacement in cementitious products. The focus was on appraising the influence of the addition of CW on the fresh and hardened properties of cementitious materials, such as cement paste, mortar, vibrated concrete, and self-compacting concrete. The reviewed literature attested to the potential pozzolanic activity of CW, thereby supporting the viability of such substitutions. The utilization of CW at lower substitution levels produces satisfactory workability. The strength level of the composites incorporating up to 15% CW is either superior to, or comparable with, that of a control mix containing no ceramic additive. Benefits to the durability performance of CW-additive cement are apparent, prompting the prospective usage of such additives even at high replacement levels of up to 40%. Microstructural investigations have substantiated the densification and refinement of the pore structure of cement resulting from CW-related pozzolanic activity. This evaluation indicates that CW usage presents a viable choice for attaining favorable properties in cement composites while concurrently realizing ecological benefits.

This study focused on determining the concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in olive trees components grown in an area with natural radionuclides (Hausha, Jordan), and in the corresponding soil samples via gamma-ray spectroscopy (GRS) and inductively coupled plasma-mass spectroscopy (ICP-MS). In addition, the transfer factors (TFs) and the effects of selected soil properties on the uptake of these radionuclides were explored. Results indicated that the mean activity concentration of ²³⁸U in soil samples is 33.26 Bq/kg while no ²³⁸U was detected in any plant part. For ⁴⁰K, the mean activity concentration in soil samples is 486.30 Bq/kg, in olive fruits reached a value of 577.77 Bq/kg and in olive oil is 17 Bq/kg. As for ²³²Th, in soil is 33.04 Bq/kg, in olive fruits is 4.30 Bq/kg, and was not detected in olive oil. The concentration of ²³²Th in olive fruits exceeded the recommended limiting value of 0.5 × 10⁻³ Bq/kg and no given reference value for ⁴⁰K exists. Moreover, the soil organic matter content and alkalinity influenced the uptake of these radionuclides.

The standard design for the underground disposal of high-level nuclear waste consists of a carbon steel container that hosts the waste shielded by a 5-cm-thick layer of corrosion-resistant native copper (Cu°), which is surrounded by a 35-cm-thick bentonite buffer. The accessory minerals in the buffer strongly influence the corrosion depth of the Cu° shield. The reactive-transport modeling shows that a buffer containing calcium sulfates (gypsum or anhydrite) has a Cu° corrosion depth that is three to eight times greater than that without calcium sulfates, depending on the groundwater chemistry. The presence or absence of iron oxides (hematite, goethite, or lepidocrocite) has a minor effect according to reactive-transport modeling. However, mineral equilibrium thermodynamics implies that the presence of iron oxides significantly reduces corrosion depth. Such a model is supported by the genesis of natural native copper deposits: the hydrothermal fluids interacted with iron oxide while depositing native copper.

The main aim of this study was to remove a model antibiotic, that is, metronidazole (MET), using TiO₂ coated on granular activated charcoal (GAC–TiO₂) and graphene oxide (GO) embedded in chitosan (CS) by adsorption and photocatalysis. Analyses including scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Fourier transform Ramen spectroscopy, X-ray diffraction, and the BET method, along with batch adsorption and photocatalysis results, were used to compare the performance of composites. The ultraviolet C (UVC)/CS–GO system (99.4%) showed higher MET removal compared with UVC/GAC–TiO₂ (97.4%) at 10 mg L⁻¹ initial MET concentration; however, the total organic carbon reduction was greater in the GAC–TiO₂ system (78.4%) than in the CS–GO system (72.3%). After 120 min, the UVC/GAC–TiO₂ and UVC/CS–GO systems showed maximum MET removal rates of 0.0561 and 0.04 min⁻¹, respectively. By contrast, batch adsorption experiments indicated that CS–GO has approximately 20 times greater MET adsorption capacity than GAC–TiO₂. Furthermore, CS–GO was found to be superior in MET removal than GAC–TiO₂ in a reusability study (i.e., for 15 treatment cycles), owing to higher adsorption capacity. Overall, the results indicate that CS–GO could be a potential composite for continuous photocatalytic experiments in the framework of emerging contaminant removal.

Green synthesized TiO₂ (CG-TiO₂) was prepared from Titanium isopropoxide (TTIP) precursor using aqueous leaf extract of Calotropis gigantea (CG). The CG-TiO₂ was prepared with different mixing ratios of CG and TTIP varying from 1:3 to 1:5 and at different synthesis conditions, that is, mixing time, temperature, and calcination temperature. Morphological analysis indicated spherical nanoparticle clusters of CG-TiO₂ with particles of an average size of 42 nm. The study indicated visible light excitation of CG-TiO₂ and effective removal of Congo red from aqueous solution under visible light irradiation. A maximum Congo red removal efficiency of 97% was obtained within 2 h under the following conditions: Sample B (30 g leaves in 100 mL distilled water boiled for 2 h at 90°C); TTIP:CG – 1:3; mixing time and temperature – 2 h and 27°C, respectively; calcination temperature – 300°C.

In order to study the efficiency of arsenic (As) removal from gold-mine tailings by electrokinetic-assisted phytoremediation (EAPR), a constant direct current (DC) electric field of 1 V/cm (3 h per day) was applied to dwarf Napier grass (Pennisetum purpureum cv. Mott) seedling pots. Furthermore, the influence of the enhancing agent on As uptake was compared with the addition of ${\mathrm{PO}}_4^{3-}$ at levels of 0.7 (P1), 1.4 (P2), and 2.8 (P3) mmol/kg, and ethylenediaminetetraacetic acid (EDTA) at levels of 2.5 (E1), 5 (E2), and 10 (E3) mmol/kg. The increase in the enhancing agent level resulted in a significant (p ≤ 0.05) decrease in aboveground biomass and SPAD values. This was due to the high levels of the enhancing agent inducing a high As concentration in the aboveground parts of the grass. The optimum level of P2 caused the labile As at the anode to form mainly in the charged species throughout the experiment. This caused P2 to have 2.62 µg/g of As in its aboveground parts, which was 38.93% of the total accumulated As. The optimum level of E1 returned a similar As concentration of 2.27 µg/g in the aboveground parts, which was 41.34% of the total accumulated As, corresponding to the highest translocation factor (TF). Moreover, As K-edge X-ray absorption near-edge structure (XANES) spectra of mine tailings at the anodes of P2 and E1 indicated that the oxidation of As(−I) to As(V) increased. This caused As in mine tailings to be more phytoavailable and also enhanced the translocation of As from the underground to the aboveground parts of the grass.

This study aims to investigate the geotechnical and chemical properties of sand–clay mixtures contaminated with lead and zinc. To prepare the specimens, two kinds of mixtures were studied. Sand–kaolinite and sand–bentonite with different clay fractions were investigated through consistency limits, pH measurement, direct shear test, unconfined compression test, batch adsorption experiment, and electrical resistivity. The heavy metal contaminants were lead nitrate and zinc nitrate hexahydrate, and contaminated specimens were prepared in the laboratory with desired concentrations (i.e., 1.5% and 3% by weight of the dry soil). Based on the obtained results, the presence of kaolinite in specimens decreased the angle of friction. On the other hand, the presence of bentonite in mixtures increased the friction angle. Moreover, sand mixtures including bentonite showed a better capability to adsorb heavy metals than sand–kaolinite mixtures. The electrical resistivity of all the sand–clay mixtures decreased with the increase of concentration. Owing to the acidity feature of heavy metals, the pH of the contaminated soil solutions decreased. Moreover, the adsorption of heavy metals in soils including bentonite was more than that of sand with kaolinite.

Size-resolved aerosol mass concentrations and concentrations of inorganic water-soluble ions (WSIs) were measured in four seasons, from December 22, 2016 to November 28, 2017, in Nanjing, China. Water-soluble ions were the main components of the atmospheric particles in Nanjing. The WSIs mainly comprised fine particles, especially in the 0.5–1-μm size range. Sulfate $({\mathrm{SO}}_4^{2-})$, nitrate $({\mathrm{NO}}_3^{-})$, and ammonium ${(\mathrm{NH}}_4^{+})$ (SNA) were the major WSI components. The secondary transformation products of the SNA WSIs were mainly distributed in the fine component of the total WSIs, while the coarse component contained a large amount of soluble mineral dust, comprising calcium (Ca²⁺), sodium (Na⁺), and magnesium (Mg²⁺). The mass concentrations of the total WSIs showed clear seasonal variations, with much higher concentrations in autumn and winter than in spring and summer. The mass concentrations of the WSIs increased significantly during pollution episodes, especially in the fine particle size component. The increases in the mass concentrations of WSIs on polluted days were mainly driven by the accumulation of secondary ions (i.e., SNA) in the fine component, while the contribution of the primary ions (Ca²⁺, Na⁺, and Mg²⁺) was relatively small. Ion charge-balance analysis showed that, for the inorganic WSIs, the charge concentration of the cations was greater than that of the anions in all seasons, with this phenomenon being strongest in spring and weakest in winter and strongest on nonpolluted days and weakest on heavily polluted days.

Increasing use of inorganic nanoparticles in consumer products and industrial processes has resulted in greater presence of these nanoparticles in wastewater, and it is important to understand the occurrence and characteristics of this material in wastewater. The objectives of this research were to further develop and improve techniques to identify, quantify, and characterize these inorganic nanoparticles, and investigate their presence in wastewater from a large community with diverse wastewater sources. Single-particle inductively coupled plasma mass spectrometry (spICP-MS) was utilized, along with other nanoparticle characterization techniques. Wastewater samples were collected over monthly time intervals from a local wastewater treatment facility. Extraction and concentration protocols were developed to prepare samples for analysis using ICP-MS, scanning electron microscopy (SEM), dynamic light scattering (DLS), and atomic force microscopy (AFM). Results indicated the presence of detectable quantities of a wide range of inorganic nanoparticles in wastewater samples, with significant variability over time. As treated municipal wastewater is frequently discharged to the environment, the findings of this research are of importance to those determining environmental impacts.

This research focuses on the potentiality of calcium hydroxide (Ca(OH)₂) and sodium hydroxide (NaOH) columns in augmenting the geoengineering and geoenvironmental properties of sedimented ash beds. Model ash beds were prepared and stabilized with NaOH and Ca(OH)₂ of 9 M concentration. The bearing resistance, collapse potential, hydraulic conductivity, pore characteristics, concentration of elements, and pH of the pore fluid were measured. The strength contours formed around chemical columns were found to be bell-shaped. The magnitude of strength development in the Ca(OH)₂ column was relatively insignificant and limited to the peripheral region of the column, whereas it spread to a greater extent in a NaOH-treated ash bed. Calcium-based hydration compounds were found in a Ca(OH)₂ column-treated ash bed whereas an ash bed column treated with NaOH displayed both geopolymeric as well as calcium-based hydration compounds. The encapsulation of leached elements in the reaction matrix reduced their concentrations in leachate. The concentration of elements in leachate was identified to be influenced by the pH value and stabilization period. Both the chemical columns were found to be effective. However, the NaOH column showed a significant improvement in bearing resistance and in situ dry unit weight along with reducing the hydraulic conductivity, collapsibility, and migration of leachable elements.

In a long-duration study, the performance of a physicochemical system for the treatment of raw graywater––namely, coagulation followed by continuous saturated-sand filtration––was investigated. Graywater coagulated using alum at the optimum dose was used as the influent to the filter. The filter was operated for 101 days in downflow mode at a flow rate of 10 L/day (hydraulic loading rate of 320 L/m²/day). The results showed that the quality of the raw graywater was highly variable, even though the source of the graywater was the same. The raw graywater had a mean turbidity and chemical oxygen demand (COD) concentration of 49 NTU and 157 mg/L, respectively. Coagulation-flocculation was very efficient at removing turbidity, COD, and fecal coliforms (FCs), achieving 94%, 65%, and 96% removal, respectively, but failed to meet the different reuse standards. The combined treatment of coagulation followed by sand filtration showed 99%, 91%, and 94% overall removal of turbidity, biochemical oxygen demand, and COD, respectively. The treatment also resulted in >99% removal of FCs, while phosphates were reduced to below detectable limits. The results of the study indicated that effluent quality was not significantly affected by variations in the influent characteristics, and the filter effluent met different reuse standards.

The use of mobile phones and discarding them before or after their end-of-life has become a recent trend. This practice increases environmental pollution and health hazards worldwide. Besides pollution, mobile phones and their batteries emit electromagnetic radiation during their lifetime and after their end-of-life. This study aims to measure ionizing radiation this is emitted by mobile phones and mobile phone batteries using a Geiger–Muller (GM) counter. To conduct this study, 15 active, 10 end-of-life mobile phones, and 10 waste lithium-ion batteries will be evaluated. Emissions from these devices will be compared with background radiation. The maximum counts per minute (CPM) for waste mobile phone batteries was 18 CPM and the minimum was 14 CPM for waste batteries and waste mobile phones. The average and standard deviation values for background radiation was 14.000 ± 0.404 CPM. The average and standard deviation values were 16 ± 1 CPM for active mobile phones, 16.00 ± 0.73 CPM for waste mobile phones, and 16.00 ± 1.19 CPM for waste batteries. Therefore, the continuous use of mobile phones and stockpiling should be avoided, and proper management processes should be developed to minimize environmental pollution and human health hazards.

The aim of this research was to compare the environmental impacts of applying thermal vitrification, recycling in clinker furnace, or final disposal of asbestos in a hazardous waste landfill in a case study in Argentina. The methodology of life cycle assessment (LCA) was used to compare scenarios through a series of midpoint and endpoint indicators. Recycling asbestos in a clinker furnace was found to be the most beneficial alternative. Transport stage contributed the most to the negative impacts of the actual management system, while vitrification was the most important one in the corresponding alternate scenario. Two sensitivity analyses were performed to compare fuel consumption variables and different scopes for the system. It was observed that changing the scope of the analysis led to major modifications in the results, reversing the trend of considering recycling as the best option. However, the initial scope was considered adequate. On-site thermal treatment was environmentally comparable to the current transport stage and might be a game changer if risk of asbestos release is considered under current conditions of landfilling.