Journal of Hazardous, Toxic, and Radioactive Waste

The rapid increase in demand for natural resources owing to industrial growth and urbanization has paved the way for the utilization of industrial by-products (i.e., fly ash, bauxite residue, steel slag, copper slag, phosphogypsum) as (1) a replacement or (2) an additive for many prevalent construction materials. Moreover, studies have also reported valorization (e.g., extraction of minerals, rare earth metals) of industrial by-products for industrial and commercial applications. In this context, to enable potential and effective utilization of these by-products, with minimal impact on the ecosystem, a better understanding of their physical, chemical, mineralogical, and morphological characteristics is essential. Meanwhile, the presence of hazardous and toxic constituents in industrial by-products that have short- and long-term impacts on nature leads to challenges in their utilization and needs to be tackled. Of late, it has been realized that most studies to mitigate the potential threat of by-products are confined to (1) pH neutralization, (2) leachate management, (3) air pollution control, and (4) heavy metal removal, and little effort has been made to determine the presence and emission of radioactive elements (e.g., ²³⁸U, ²³²Th, ⁴⁰K, ²²⁶Ra, ²²²Rn gas) in them. Under these circumstances, an extensive literature review of the characteristics and utilization of industrial by-products, with an emphasis on their radioactivity levels, is made in detail. A critical synthesis of the existing literature reveals that the radioactive measure, I-index, of phosphogypsum, red mud, slags, fly ash, and so on, exceeded by 1.5–7.5 times the permissible radiation limit [recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the International Atomic Energy Agency (IAEA)]. Moreover, considering the hazardousness associated with exposure to such by-products, efforts are to be invested in developing handy tools or methodologies for their detection, and possible remedies for their mitigation, before their utilization for various applications.

The present investigation reports the production of pyrolytic plastic oils and their performance in compression ignition (CI) diesel engines with different oil and additive blends. Experimental investigation has been conducted on a four-stroke single-cylinder variable compression diesel engine at a steady engine speed of 1,500 rpm with a different blend of pyrolytic plastic oil (PPO) and ethanol with diesel for various load conditions. Parametric studies are conducted for blend proportion of 10%–20% and compression ratio of 16–18. The engine thermal efficiency is found to be augmented significantly by 2.67% and specific fuel consumption reduced by 0.59% at maximum engine load for 60D20PPO20E to that of diesel. The brake specific fuel consumption is also diminished for fuel mixtures by increase of concentration of additives in the fuel blend than diesel. The overall improvement in engine performance is found at 20% blend of PPO and ethanol in diesel with the highest compression ratio of 18. The novel correlation for brake thermal efficiency with respect to influencing parameters has been developed.

One of the major problems that every part of the world is fighting today is waste production and how to deal with it, that is, waste management. In India, every city periphery becomes a dump yard for tonnes of waste. This study focused on reducing and reusing the already dumped waste through the technique of landfill mining. The objective of this paper is to investigate the potential use of soil-like material from municipal solid waste (MSW) to replace it as fill material, for which chemical as well as geotechnical investigations were made on MSW fines. Further, this waste is reinforced with fibers (part of the waste itself) in a portion of 0.5%, 1%, 2%, 4%, 8%, and 10% by weight and is investigated for optimum quantity for geotechnical purpose. The MSW fines characterized as light-weight, nonplastic silty sand-type material with good shear strength properties (cohesion and friction angle from 31.37 to 42.19 kPa and 26.69° to 30.74°, respectively) with an organic content of 5.9% and slight acidic behavior. The addition of fibers enhances the strength properties of MSW fines and optimized results were found for 8% fiber. The results from this study can be an initial step to check the potential use of MSW in various civil engineering fields.

The leaching kinetics of lead (Pb) from galena using hydrogen peroxide (H₂O₂) in trichloroacetic acid (TCA) solution will be explored in this study. The influence of temperature, stirring speed, concentrations of H₂O₂ and TCA as well as particle size, will be analyzed. The dissolution kinetics followed a shrinking core model, with the diffusion of some species as the rate-determining step. The value of activation energy obtained in this study was 39.89 kJ/mol, which meant that the leaching of Pb was controlled by a surface chemical reaction. The reaction order for H₂O₂ was 0.55 and the order of reaction for TCA was 0.44. Overall, the leaching of Pb from galena relied mainly on the concentrations of TCA and H₂O₂, temperature, particle size, and stirring speed. The combination of TCA and H₂O₂ leached substantial amounts of Pb from galena.

The disposal of hazardous wastes poses a serious threat to the environment because of their long period of degradation. This study is based on an experimental approach that aims to analyze the effect of high temperatures on the characteristics of lightweight masonry mortars incorporating expanded or cellular PVC (EPVC) aggregates from advertising and decorative display hazardous waste products. This article presents an experimental study of the physicomechanical and thermal properties of lightweight composite mortars based on expanded PVC (LMEPVCs) in which natural aggregates were replaced by EPVC aggregates at different mix proportions. The LMEPVCs were heated to temperatures of 450°C, 650°C, and 850°C. In addition, this study focused on the evolution of mass loss, apparent volume, porosity accessible to water, microstructure, mechanical strength, ultrasonic pulse velocity, dynamic elastic modulus, and thermal conductivity of various LMEPVCs as a function of applied temperature. The results obtained showed that these LMEPVCs retained their initial properties even after exposure to high temperatures; their properties were found to be similar to those of reference mortar. Moreover, the incorporation of 75% EPVC aggregates in the cement matrix revealed that the formulated composites had the capacity to resist thermal loads up to a temperature of 650°C. It was therefore concluded that the incorporation of EPVC in masonry mortars may be viewed as an environmentally friendly approach for recycling this type of nonbiodegradable waste.

Xenobiotics are newly identified contaminants, recently discovered to be present in the environment and possessing potential threat to different components of the ecosystems due to their inherent toxicity and endocrine-disrupting nature. Moreover, due to their recalcitrant nature, these emerging contaminants are not effectively removed by existing conventional wastewater treatment technologies. In this regard, the present review focuses on the development of electrochemical oxidation (EO) as a sustainable and efficacious technology for the treatment of wastewater containing xenobiotics. The technology of EO works on the process of in-situ generation of highly reactive hydroxyl radicals (OH˙), commonly via metallic cathode catalysts due to the application of electric current, which further oxidizes and is thus effective in eliminating pollutants such as xenobiotics from wastewater. This mini-review will aid in understanding the application of EO for the removal of xenobiotics from wastewater and different metal catalysts employed in EO for the production of hydrogen peroxide. Moreover, the critical factors affecting the performance of EO for xenobiotics removal have also been elucidated for enhancing the understanding of the readers in terms of scaling-up of an EO reactor.

Malaysia is considered as a major palm oil producer in the world. Therefore, it is vital to utilize an environmentally friendly and inexpensive method to treat palm oil mill effluent (POME) in Malaysia. Nowadays, the use of natural absorbent to remove pollutants from POME has gained remarkable attention. The main objective of this research was to investigate the effect of calcinated limestone on turbidity removal and analyze the removal rate of pollution of POME. A column studies was conducted using different particle size of limestone (4, 12, and 20 mm), raw and calcinated at 800°C and 600°C at filtration rates of 20, 60, and 100 mL/min. An experimental model was conducted using central composite design (CCD) in response surface methodology (RSM). According to analysis of 3D surface respondents, the first optimum condition was at 800°C with 2 h of calcination time, flow rate of 20 mL/min, and limestone size of 4 mm. The second optimum condition was calcinated limestone at 600°C using a lower flow rate and smaller size of calcined limestone (CLS). The first and the second optimum conditions achieved turbidity removal of 68% and 62%, respectively, both of which outperform raw limestone with removal rate of 55%. Equilibrium isotherms in this study were evaluated using the Langmuir and Freundlich isotherms. The results showed that adsorption isotherm data is more fit to the Langmuir isotherm, with 0.95 R² compared with 0.85 R² for the Freundlich isotherm at 800°C.

This study will investigate the removal of nitrate from groundwater by aluminum–aluminum (Al–Al) electrocoagulation (EC) using response surface methodology. Box–Behnken design (BBD) will be used to investigate the mutual interaction effect of important process parameters, such as current density (A), electrolysis time (C), and spacing (B) on nitrate removal efficiency (NRE %) from four groundwater samples with different initial nitrate concentrations. Experiments will be performed according to the BBD matrix and the data obtained fitted well to a quadratic model that demonstrated a good association between the predicted and experimental values with >R² = 0.97 for all samples. In ANOVA studies, a p-value of <0.00001 was obtained, which confirmed the suitability of the regression models (p-value <0.05). In addition, a small value for the coefficient of variation (3.95%, 1.65%, 2.90%, and 3.84%) for all the samples indicated a higher degree of accuracy and the reliability of the experiments. ANOVA results and three-dimensional (3D) plots suggested that A and C were the main process parameters in this study and B had a negative effect on NRE %. Maximum NREs (%) of 92.5 (106 mg/L), 91.5 (133 mg/L), 83.5 (148 mg/L), and 71 (231 mg/L) were obtained at C = 1.6–2.78 h, A = 0.065 A/cm², and B = 1 cm. In addition, for the feasibility of EC at an industrial scale, the management of the generated sludge was explained by its characterization using scanning electron transmission microscopy (SEM). This study concluded that the EC approach might be a promising technique for application to nitrate removal from groundwater.

Several environmental indices have been developed over the last five decades. These indicators have been used by decision makers. However, it is becoming difficult for decision makers to understand the relevance and meaning of these indicators because of factors, such as technological advancement, reliability of these indicators over time, the emergence of new parameters, and suitability of these indices that have posed questions on the relevance of these indicators. Therefore, revalidation or reassessment of the environmental indices is required. In this paper, a case study on the leachate pollution index (LPI) that was developed using the Delphi technique will be conducted. The procedure that was used for the development of the index did not accurately reflect the opinion of the experts that have responded to the questionnaire. In addition, shortcomings in the formulation of the LPI are highlighted and, based on this paper, it was concluded that if the correct procedure was adopted, the LPI might contain different parameters as constituent pollutants. Therefore, this paper highlights the need to reassess environmental indices.

The present study analyzes the effect of salinity on crop growth and root zone soil moisture dynamics. A newly developed root water uptake (RWU) model was used for simulation of soil moisture and RWU for irrigation field experiments where paddy was grown with irrigation water with varying salinity concentrations (0.5, 7.9, 14.7, and 21.2 dS/m). The growth of the crop was monitored regularly, and crop parameters such as leaf area index (LAI) and root depth along with the soil moisture profile were measured during the crop growth period. The nonlinear parameter for the RWU model was estimated using an empirical relation in terms of observed crop variables (LAI and root depth) for each saline irrigation condition. Root zone soil moisture and RWU for the prevailing hydrometeorological conditions during the crop period and soil-crop parameters were simulated for the analysis. The irrigation experiments show that the growth of the crop is significantly affected by the salt concentration in soil-water, resulting in a decrease in the crop canopy (LAI) and root depth decreases with an increase in the salt concentration. The model simulation results show that an increase in salt concentration in irrigation water results in reduced root water extraction and reduced moisture content in the soil profile.

Leaching characteristics of chromium ore processing residue (COPR) for the long term (simulating a 20-year leaching scenario) were investigated using laboratory flow-through column testing with synthetic rainwater and groundwater for 250 pore volumes of flow (PVFs). Four saturated column experiments simulated the long-term leaching of chromium (Cr) from two types of COPR [unweathered, gray-black (GB) and weathered, hard-brown (HB)] via advective groundwater and rainwater flow. The release of total [Cr(T)] and hexavalent Cr [Cr(VI)] from GB and HB COPR showed peak concentration before 5.5 PVFs and decreased significantly thereafter. The concentrations of Cr(T) and Cr(VI) from GB and HB COPR reached a steady state (5–20 mg/L) after 150 PVFs under groundwater and rainwater permeation. A substantial residual (>65%) of Cr(T) in the COPR was found after the column tests and continued releasing for an even more extended period (>250 PVFs). Higher concentrations of Cr(T) and Cr(VI) were released from COPR when permeated with groundwater relative to those with rainwater due to the highly alkaline (pH = 12.0) environment. Amorphous compounds may be a vital sink related to the release of the Cr from COPR, which can explain the higher release of Cr from HB COPR (33.2% and 22.5% cumulative leaching in groundwater and rainwater, respectively) than that from GB COPR (21.3% and 19.8% cumulative leaching in groundwater and rainwater, respectively). The temporal leaching behavior of Cr(T) obtained from the experiment was used as the input of a numerical model to investigate the long-term transport of Cr(T) through different soil substrates (sand or clay) as well as a bentonite cutoff wall. In an area with a sandy substrate of high permeability, a sand–bentonite cutoff wall is shown to control the transportation of Cr in the long term effectively.

Release of different heavy metals from various industries is a significant environmental hazard worldwide. In order to reduce the threat from these chemicals, different treatment methods are needed to make them harmless. This study approaches the problem by examining the effect of gypsum content for immobilization of selenium oxyanions selenite and selenate, and sulfate, with calcium sulfoaluminate belite (CSAB) cement-based ettringite binder systems. The study has two experimental sections. In the first section, an industrial filter sludge with high concentrations of selenium and sulfate is immobilized with CSAB and varying amounts of gypsum. The immobilization is efficient and reducing the gypsum amount in the hydrating mixture enhances the incorporation of both selenium and sulfate. The binding occurs through encapsulation and incorporation into ettringite and other hydrated phases. In the second section, two reagent grade sodium–selenium salts, sodium selenite and sodium selenate, are mixed with CSAB and varying amounts of gypsum. The immobilization is not effective and ettringite is not formed in large quantities, most likely due to high sodium content in the reacting system.

The existence of uncertainties in decision-making has given rise to multicriteria decision-making to achieve results that weigh in the effects of uncertainty. This study presents a method for selecting the best alternative for treated wastewater reuse based on gray system theory (GST). Alternatives and appropriate decision criteria for wastewater reuse are determined by experts. The criteria are weighed with the analytical hierarchy process (AHP) method, and the best wastewater-reuse alternative is then selected based on the evaluation based on distance from average solution for gray water (EDAS-G). Results of an example demonstrate wastewater reuse in the environmental sector receives the highest priority among several alternative uses.

Platinum group metals (PGMs), namely, Ru, Rh, and Pd, were removed simultaneously from molten borosilicate glass containing simulated high-level waste (HLW), using Sn as the solvent metal. The metal and glass phases were separated from each other after the melting was completed. The metal and glass phases were examined using X-ray diffraction and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis; the composition of alloy phase was analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES). The percentage of recovery of the metal phase was 80%–87%. The metallic tin phase was found to contain PdSn₄, Ru₂Sn₃, Ru₃Sn₇, and Pd_0.15Rh_0.15Ru_0.70 intermetallic compounds, which crystallize in orthorhombic, tetragonal, cubic, and hexagonal structures, respectively. On dissolving the alloy in aqua regia, Ru₃Sn₇ and Pd_0.15Rh_0.15Ru_0.70 were found to remain as an insoluble residue. The insoluble character of Ru₃Sn₇ and Pd_0.15Rh_0.15Ru_0.70 affects the material balance of each element in the glass and metal alloy phases. The PGMs were separated to the metal alloy phase along with significant quantities of Fe, Te, Ni, and Mo, leaving behind Cs, Sr, and Zr in the glass phase. The recovery of PGMs has dual benefits; the removal of PGMs facilitates smooth vitrification of the waste by Joule heating. The other benefit is that of recycling PGMs (which are rare precious metals) from the waste.

Investigations on the kinetics of leaching lead from galena (PbS), using acetic acid (HAc) solutions in iron(III) chloride (FeCl₃) solutions, were conducted using shrinking core models. The effects of operational parameters, such as temperature, acetic acid iron(III) chloride concentration, and galena particle size, on the leaching process were also studied. The results revealed that the rate of galena dissolution was controlled by surface chemical reaction under all the experimental conditions examined. The empirical reaction orders of the leaching kinetics, with respect to iron(III) chloride and acetic acid concentrations, were 0.562 and 0.274, respectively, with an apparent activation energy of 60.82 kJ mol⁻¹ in the temperature range 313–353 K. The leaching of galena using acetic acid solutions oxidized with iron(III) chloride showed a good leaching rate of lead acetates and, hence, combined acetic acid/iron(III) chloride leaching would make a relatively eco-friendly lead recovery system.

This study focuses on the optimization and application of mill scale–derived magnetite particles for the adsorptive removal of arsenic (As) from groundwater. The reverse coprecipitation method is applied to synthesize the magnetite from the mill scale, a byproduct of the iron and steel industry. The independent variables (initial As concentration, pH, contact time, and adsorbent size) affecting the adsorption process were optimized by central composite design of the response surface methodology (RSM). The analysis of variance (ANOVA) results showed that all the independent variables significantly influenced the adsorption capacity. ANOVA analysis exhibited a good fit between the experimental values and the quadratic model predictions, thus resulting in R² of 0.986. The P-value (<0.0001) displayed the significance of the model at 99% level. The P-values for pH, As(V) concentration, particle size, and contact time are determined as <0.0001, <0.0001, 0.0002, and 0.0009, respectively. The experimental optimization of batch adsorption parameters revealed 100% As(V) removal efficiency with pH 7, particle size 75 µm, 120 min contact time, and 550 µg/l initial concentration. At the maximum initial concentration (1,000 µg/l), the arsenic removal efficiency was 78% when the pH, particle size, and the contact time were 5, 45 µm, and 120 min, respectively. The reproducibility of adsorption experiments at higher concentration (1,000 µg/l) under optimal conditions confirmed the adsorption capacity 8.13 ± 0.08 mg/g.

Department of defense (DoD) hand grenade training ranges have implemented alkaline hydrolysis, which is the practice of applying hydrated lime [Ca(OH)₂] to range soil, to manage the deposition of Composition B components, such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT). This paper will analyze hydrated lime effects on soil pH and the degradation of munitions constituents with time. At one DoD hand grenade training range, lime treatment produced higher soil pH values and RDX concentration reductions by eight orders of magnitude, some achieved concentrations in the low parts per trillion (ppt). The presence of calcite (CaO), a reaction product of Ca(OH)_2, in field samples confirmed that alkaline hydrolysis reactions occurred in the soil matrix. In total, 5 months after the addition of lime to range soils, RDX was detected in collected field samples in small quantities. Column and lysimeter studies that use spiked native soils will be conducted to understand the effects of lime loading on RDX leachate and surface water runoff for site soils. The simulation efforts that used the training range environmental evaluation and characterization system (TREECS) modeling software predicted the reduction in aquifer RDX concentrations from the application of lime to the hand grenade range surface soil layer. The simulations verified the alkaline hydrolysis application parameters identified ex situ.

This study assessed the groundwater vulnerability of the Rana groundwater basin, Odisha, India. The study attempts to optimize the DRASTIC method by modifying the weights and ratings assigned to the DRASTIC parameters using the analytical hierarchy process. Sensitivity analysis has been carried out to quantify the influence of each parameter. The groundwater vulnerability results obtained from both DRASTIC and modified DRASTIC methods were validated using the water quality index (WQI) values computed through groundwater quality data at 25 sampling locations. The results revealed that the index values generated through modified DRASTIC possessed a higher correlation with the WQI compared with the original DRASTIC method. The groundwater level and net recharge were found to be having a greater influence on groundwater vulnerability. The obtained vulnerability maps from the modified DRASTIC method revealed that about 70% of the area was under very low to low vulnerable zones, whereas 14% of the area was under high to very high vulnerable zones. It was also observed that most of the high to very high vulnerable zones were located on the agriculturally dominated areas lying in the northern part of the basin. The result obtained will play an immense role in adopting management practices to conserve the groundwater quality of the study basin.

Coal-fired power plants are major emitters of mercury, a toxic element of global concern, to the atmosphere. Although more than 100 coal-fired power plants exist in India, only a limited number of studies have assessed mercury levels in the soil surrounding these power plants. Here, we report the concentrations of mercury in the soil around a 2,600 MW coal-fired “super thermal power plant” in southern India and conduct a human health risk assessment for exposure to soil mercury. It was found that concentrations of mercury in soil were less than or similar to those observed in India or other parts of the world (2.4–40.2 µg/kg). Assessment of soil quality indexes, contamination factors (CFs), and geoaccumulation indexes (I_GEO) suggests soil to be enriched in mercury compared with a local background (CF = 1–9, I_GEO < 0 to >3). Concentrations of mercury in soil were inversely correlated with the distance from the power plant, but intermediate increases were also observed, owing to the interfering influences of an opencast coal mine, ash pond, or urban area. Human health risk assessment indicates that infants are at higher risk than adults, but the overall health hazard remained low (hazard index <0.05).

Removal of dyes from industrial effluent is currently a major ecological issue. Several researchers have stated that electrocoagulation (EC) is an effective technique for the removal of dyes. Therefore, in this study, the removal of Acid Violet 17 (AV 17) dye by EC that uses plain and extended surface electrodes will be performed. The effect of major factors, such as polarity change, pH, current, spacing, speed, and sodium chloride (NaCl) on dye removal efficiency will be investigated using aluminum (Al) and iron (Fe) electrodes. In this study, the maximum dye removal obtained using an extended surface electrode (100%) will be compared with a plain electrode (95%) that used Fe–Fe electrodes. Further, the performance of the EC process was confirmed with different electrode configurations, such as normal, series, and induced mode. The EC process that used extended surface electrodes required less time and had lower economic operating costs for the treatment of synthetic and actual effluent. The results from this study confirmed that an EC process could be a sustainable option and Al–Al and Fe–Fe electrodes in a monopolar configuration was the best mode for the removal of dyes.

Probabilistic analysis of the soil–water characteristic curve (SWCC) is essential for the application of reliability-based design (RBD) in unsaturated geotechnical engineering projects. Conventional frequentist analysis requires a large number of data points to minimize statistical uncertainty. However, obtaining large regional/site-specific datasets of SWCC of bentonite is practically difficult owing to time and cost constraints. A common approach in the literature is to supplement the limited site-specific data with prior knowledge using a Bayesian approach. However, almost all the works are limited to non-clayey soils and utilize non-informative uniform priors for SWCC parameters. Therefore, this technical note proposes the incorporation of global SWCC distribution with site-specific data for probabilistic analysis of SWCC of bentonite. Twelve SWCCs of bentonite are experimentally measured in this study and a copula-based global/generic distribution for SWCC of bentonite from the literature is utilized. It is shown that incorporating global distribution as an informative prior can significantly reduce the uncertainty in the posterior distribution of SWCC parameters as compared with popularly utilized uniform priors. Finally, to demonstrate the practical significance of the proposed approach towards unsaturated RBD, a stochastic seepage analysis is conducted. It is found that the popularly used uniform priors for SWCC parameters might significantly overestimate the failure probability.