Journal of Hazardous, Toxic, and Radioactive Waste

Using grout in construction and ground improvement has been common in various industries and construction projects. However, conventional grouts often need to be improved for their composition, durability, and environmental impact. Recently, there has been increased interest in exploring alternative solutions that are more sustainable and environmentally friendly. This comprehensive review aims to unravel the limitations of conventional grouts when exploring the potential of emerging biogrout technologies to achieve environmental sustainability in ground improvement. This review begins by examining the characteristics and limitations of traditional grouts, which highlights challenges such as inadequate durability and adverse environmental impacts. Then, the focus shifts toward emerging biogrout technologies, which harness the power of microorganisms to enhance soil stabilization. The principles, applications, and benefits of biogrout technologies are discussed thoroughly, along with case studies that showcase their successful implementation. A key aspect of this review is to highlight the environmental sustainability of biogrout applications in various civil engineering projects. Life cycle analyses (LCAs) are conducted to assess the environmental impacts of conventional grout, which sheds light on their drawbacks. In contrast, the environmental benefits and challenges that are associated with biogrout technologies are examined, which provides a comparative analysis between the two approaches. This review concludes by presenting prospects and challenges in this field. It discusses advances in conventional grout formulations to address their limitations and strategies to enhance the environmental performance of biogrout technologies. In addition, integrating sustainability principles into grouting practices is emphasized to achieve long-term environmental sustainability in ground improvement projects. Overall, this comprehensive review could contribute to the advances in sustainable ground improvement practices by providing insights into the limitations of conventional grouts and exploring the potential of emerging biogrout technologies. It could be a valuable resource for practitioners and researchers who seek sustainable solutions in ground improvement that align with environmental stewardship and sustainable development goals.

Abstract

In the present work, the thermodynamic parameters for the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D), a herbicide, onto biomass-based activated carbon coated with magnetite nanoparticles (ACM) were estimated using a high-precision isothermal titration calorimeter (ITC). The obtained thermodynamic parameters, such as change in Gibb’s free energy (ΔG), change in enthalpy (ΔH), and change in entropy (ΔS), were compared with the values computed applying conventional methods using equilibrium isotherm model parameters. The thermodynamic parameters suggested that the adsorption of 2,4-D onto ACM was spontaneous and exothermic. ITC proved to be an efficient experimental method in determining the thermodynamic parameters for the adsorption process with minimal adsorbent, adsorbate, and time consumption. The application of ITC can also be extended to determine the thermodynamic parameters of various solid–liquid interactions involved in different processes.

Practical Applications

The 2,4-dichlorophenoxyacetic acid (2,4-D) is commonly used as a herbicide, and its occurrence is reported widely in aquatic bodies. Adsorption process using activated carbon impregnated with iron nanoparticles proved to be effective in removing these 2,4-D from the aquatic phase. In general, adsorption dynamics are demonstrated by isotherm, kinetics, and thermodynamic studies so that it can be extended to real-world applications. Conventionally, adsorption thermodynamic parameters are estimated from equilibrium isotherm constants. However, the determination of these parameters using the isotherm constants may not be accurate. Hence, sophisticated equipment such as isothermal titration calorimeter (ITC) can be used as an efficient tool to accurately compute the thermodynamic parameters in less time with minimal requirement of reagents.

In this research, a novel magnetic recyclable MIL-53(Fe) metal–organic framework (MOF)-derived Fe₃O₄ (wFe) photocatalyst was synthesized using waste polyethylene terephthalate (PET) plastic and iron scraps for efficient activation of persulphate (PS) to degrade salicylic acid (SA). Different characterization techniques thoroughly assessed the physicochemical and photoelectrochemical features of the synthesized photocatalyst. The wFe showed 95.45 ± 3.69% degradation and 56.73 ± 2.25% mineralization of 50 mg L⁻¹ SA within 180 min in the presence of 1 mW cm⁻² of UV fluence, 0.01 mM of PS, and 50 mg L⁻¹ of catalytic dosage. The degradation of SA in wFe/UV/PS followed pseudo-first-order reaction. Moreover, stability of wFe photocatalyst was verified by reusability analysis, which demonstrated that SA degradation and mineralization efficiency slightly declined from 95.45 ± 3.69% to 90.24 ± 2.25% and from 56.73 ± 2.25% to 43.94 ± 1.90% after the sixth run with the highest iron leaching of 0.157 mg L⁻¹, suggesting wFe possesses outstanding stability and recyclability. The findings of radical quenching and Mott-Schottky analysis showed that among different active radicals (i.e., h⁺, ${\mathrm{SO}}_4^{\bullet -}$, ^·OH, ${\mathrm{O}}_2^{\bullet -}$, e⁻), ${\mathrm{O}}_2^{\bullet -}$ was the active species majorly involved in the degradation of SA. In addition, the wFe/UV/PS system showed acceptable efficacy for the degradation of SA spiked in different real-water matrices. Finally, the mechanism involved in the degradation of SA and abatement pathways was established depending on the scavenging and liquid chromatography-equipped mass spectroscopy analysis.

Abstract

This study investigates the hazardous effect of salinity on plant growth and soil moisture dynamics in the root zone. Field irrigation experiments on paddy (Oryza sativa L.—basmati variety) with varying levels of salinity of irrigation water (0.5, 5, 10, 15, 20, and 25 dS/m) were performed for studying the effect of salt water stress on crop growth. Throughout the crop’s growth period, measurements of leaf area index (LAI), root depth (RD), and soil moisture status in the root zone were recorded. For the analysis, a numerical model was developed to simulate root water uptake (RWU) and soil moisture movement in the root zone, accounting for osmotic pressure developed as a result of the salinity. Nonlinear parameters for the RWU model were estimated based on these observations for each salinity level. By incorporating meteorological data and soil–crop parameters, the model simulated RWU and root zone soil moisture. The results of the irrigation experiments revealed that increased salinity levels in the irrigation water significantly hindered crop development, leading to a decrease in LAI and root depth. The maximum LAI in the growth period decreased markedly, from 5.19 m²m⁻² at 0.5 dS/m to 2.01 m²m⁻² at 25 dS/m, a decline of approximately 61%. Root depth also exhibited a substantial reduction, declining by up to 36%, from 69.5 cm at 0.5 dS/m to 44.5 cm at 25 dS/m. The simulation outcomes further demonstrated that higher salt concentrations in the irrigation water resulted in reduced root water uptake and decreased soil moisture content in the root zone, ultimately affecting crop yield. The reduction in root water uptake becomes notably pronounced, exhibiting an approximate decrease of 81% when salinity level increases from 0.5 to 25 dS/m. These findings shed light on the hazards posed by salinity in agricultural practices and emphasize the importance of effective management strategies to ensure sustainable crop production in the presence of salinity-induced hazards.

Practical Applications

The results of our research yield significant insights with practical applications for real-life conditions. We find that increasing salinity levels in irrigation water have a pronounced adverse effect on paddy crop growth and root water uptake. As salinity levels rise, there is a noticeable effect on crop growth i.e., decrease in leaf area index (LAI), root depth (RD), and root water uptake (RWU), which are crucial parameters for crop development. Furthermore, our findings reveal a clear correlation between increasing salinity and reduced soil moisture content, particularly at the critical depths of 20 and 40 cm below the surface. The practical implications of our research are twofold. First, it underscores the importance of carefully managing salinity levels in irrigation practices to mitigate the negative effects on crop growth and water uptake. Secondly, our study provides valuable insights for crop selection, suggesting that paddy crops may be less suitable under high salinity conditions. These results offer practical guidance for agricultural decision makers, highlighting the need for salinity control measures and informed crop selection to optimize agricultural productivity in regions with saline water environments.

In Northern India, a large quantity of rice stubble is burned in situ in agricultural fields after the rice crop has been harvested, which releases harmful gases and particulate matter into the environment. This poses a threat to the environment and the health of living organisms. Stubble burning could be prevented by utilizing the rice straw directly or indirectly. In this study, efforts have been made to explore the use of biochar that is obtained from the pyrolysis of rice straw as an adsorbent for the removal of arsenic from water, because arsenic in groundwater is a worldwide problem. The rice straw was chemically modified and pyrolyzed to obtain iron-modified biochar. The iron-modified biochar was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The adsorption optimization for the arsenic removal was carried out using response surface methodology for three adsorption parameters (e.g., contact time, adsorbent dosage, and initial arsenic concentration). The iron-modified biochar could remove 99% of the arsenic from water with 989 µg/L arsenic at an adsorbent dosage of 3.25 g/L. The leaching of iron from the iron-modified biochar was tested and was negligible. In addition, the disposal of exhausted adsorbent in municipal solid waste landfills was suggested following the toxicity characteristic leaching procedure.

Soil–water cocontamination with heavy metals and nonaqueous phase liquids (NAPLs) raises widespread concerns. Coexisting NAPL pollutants like toluene can antagonize the chemical processes employed for removing target heavy metals. This study investigates the impact of toluene on Cr(VI) adsorption by pumice-supported nano zerovalent iron (P-nZVI). The experiment was performed by passing a 10 mg/L Cr(VI) aqueous solution through a fixed-bed column in two batches, one without and the other with toluene. Results showed that toluene's copresence caused a 71.3% drop (3.14 to 0.9 mg/g) in P-nZVI adsorption capacity for Cr(VI). In toluene's absence, a Cr(VI) concentration in the effluent appeared after 60 h, while in its copresence, a Cr(VI) concentration appeared within 10 h. The average Cr(VI) concentration of the effluent increased from 5.05 mg/L in the first batch to 8.64 mg/L in the second batch. Breakthrough curve modeling demonstrated that the Thomas model best described the adsorption kinetics for the first case (R² = 0.999), followed by the Yoon and Nelson and the Clark models with R² = 0.996 and 0.994, respectively. Under toluene cocontamination, both the Thomas and the Yoon and Nelson models showed the best fit (R² = 0.996). The inverse numerical analysis determined adsorption isotherm parameters (K_s , β, η) and confirmed that the reaction followed Langmuir behavior (β ≃ 1) with slight linearity under individual Cr(VI) presence. The results from this adsorption study, supported by adsorbent characterization before and after the reaction, demonstrated the unfavorable effects of coexisting contaminants on the removal of contaminants of concern.

The concentration of persistent organic compounds, including pesticides, in aquatic environments is gradually increasing due to industrial discharge and uncontrolled runoff from agricultural fields. The advanced oxidation process is considered the most effective treatment method for the mineralization of persistent compounds. This research focused on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide by a homogeneous process involving ultraviolet irradiation and H₂O₂ (UV–H₂O₂) and utilized response surface methodology (RSM) to analyzed influences of key factors involved in processes like 2,4-D concentration, H₂O₂ dose, pH, and nitrate amount in wastewater. Results showed that 90% of the 2,4-D herbicide was degraded within 5 min of UV-C radiation (253.7 nm wavelength) corresponding to the peroxide dose of 2 mol H₂O₂/mol 2,4-D at pH 5 and a nitrate concentration of 0.25 mM. A polynomial quadratic equation was developed to envisage both time- and fluence-based rate constants. All process parameters were found to significantly affect the degradation of the herbicide. Results indicated that an increase in initial 2,4-D and nitrate concentration in solution decreases the 2,4-D degradation rate. Higher H₂O₂ dosages and pH levels indicated an intensification in the rate constant up to an optimum value. Further, an increase in H₂O₂ dosage and pH resulted in a decrease in degradation rate. Further, the optimum conditions for 2,4-D degradation by the UV–H₂O₂ process were estimated. The findings of the present work will help to design the treatment process in real field conditions with variable water matrices.

The removal of nitrogen from wastewater is one of the challenges faced by environmental engineers globally. Autotrophic denitrification is a promising method for treating nitrate $({\mathrm{NO}}_3^{-})$-contaminated wastewater because of its relatively low requirement for carbon and lesser sludge yield. Therefore, this study was aimed at investigating the autotrophic denitrification efficiency of two different dual-chamber configurations of microbial fuel cells (MFCs) in order to provide a foundation for building scalable, efficient, and sustainable denitrification systems. Analysis revealed that the maximum current density and power density were 4,327 mA/m³ and 1,441 mW/m³, respectively, in a cube-shaped dual-chamber MFC (C-MFC), whereas these values were 1,452 mA/m³ and 370 mW/m³, respectively, in an H-shaped dual-chamber configuration (H-MFC). In addition, the C-MFC and H-MFC achieved relatively high ${\mathrm{NO}}_3^{-}$ reduction rates of up to 28 and 15.6 g/m³/day, respectively. The cathodic coulombic efficiency was observed to be 57% in the C-MFC and 30% in the H-MFC. The average chemical oxygen demand removal efficiency was about 98% for both MFC configurations. High-throughput sequencing analysis revealed significant changes in the microbial community structure under different reactor configurations. The relative abundance of Proteobacteria (34.67%) and Firmicutes (18.59%) at the phylum level were higher in the C-MFC than the H-MFC, signifying that higher current generation can enhance the proliferation and microbial activity of autotrophic denitrifiers.

Global advancement of solar energy and its emerging technologies are good indicators to assess the general response of energy users to clean energy as enshrined in the sustainable development goal (SDG) 7. However, the reality that solar panels and other components would become electronic waste someday and ultimately contribute to chemical hazards in the environment is a source of concern. This study aimed to evaluate the amounts of heavy metals in solar photovoltaic (PV) modules using atomic absorption spectroscopy and estimate the health risks associated with these heavy metals. Six samples of solar PV were collected and evaluated for Chromium (Cr), Cadmium (Cd), Lead (Pb), and Arsenic (As). Using the health risk index (HRI) and the target hazard quotient (THQ), the human dangers presented by the presence of heavy metals were evaluated. The heavy metal content ranged as follows: Pb (6.00–6.25 mg/kg); Cd (0.10–1.25 mg/kg); Cr (8.00–12.00 mg/kg); and As (0.60–1.25 mg/kg). An estimate of the average weight for children and adults was used to calculate the health risk index. The result showed that health risks for children and adults are high with heavy metal concentrations escalating in the order Pb > Cd > Cr > Ar. The THQ in all metals was < 1 in all the solar PV samples, which indicates they do not pose serious health risk concerns in a single panel. However, considering the large number of waste panels, the risk would be significant. Also, it was found that there were naturally occurring radioactive materials (NORM) in the PV modules and their effects are more in the short term. Hence, heavy metals are envisaged as long-term hazards, and NORM in PV modules are envisaged as short-term hazards. Using the EPA dose compliance concentrations (DCC) (EPA-DCC), the radioactive exposures from the selected photovoltaics were proven to be directly dependent on the number of PVs in use and their distance from the PV installations. Several recommendations were made to curb death in the process of pursuing cleaner energy technologies.