ABSTRACT In situ chemical oxidation (ISCO), a remediation technology for soil and groundwater contamination, utilizes oxidants that can impact the soil environment and indirectly influence soil CO 2 emissions. Understanding these emissions may support more sustainable ISCO applications by enabling adjustments to treatment conditions that limit unnecessary CO 2 release. This study assessed the effects of ISCO on soil CO 2 emission rates and total bacterial counts by evaluating three common ISCO oxidants: hydrogen peroxide (HP), sodium persulfate (SPS), and potassium permanganate (PM), also in combination with various activation methods. CO 2 emission rates from the soil slurry system were measured using a closed static chamber method and expressed in nanograms of CO 2 per gram of dry soil per hour (ng CO 2 g ds –1 h –1 ). Under stable conditions, soil CO₂ emission rates were ranked as follows: SPS groups (2.0~4.0) > PM group (1.9–3.1) > HP groups (0.6–1.8) ≈ original soil (0.4–1.0), while total soil bacterial counts (CFU g ds −1 ) ranked as: PM group (~10 7 ) > HP groups (~10 6 ) > original soil (~5.0 × 10 6 ) > SPS groups (~10 4 –10 6 ). Most oxidant activation treatments led to higher CO 2 emission rates and soil bacterial counts, except under alkaline activation. These findings demonstrate the influence of different ISCO processes on soil CO 2 emissions and offer a baseline for emission rates during ISCO remediation.

ABSTRACT Excess nutrient loading is a global challenge affecting water quality. Biochar has emerged as an effective tool for reducing nutrient loads through adsorption, whether as a soil amendment or an edge‐of‐field treatment. This study evaluated biochar derived from two commonly available agricultural byproducts, walnut and pistachio shells, for their capacity to remove nitrate and phosphorus from aqueous solutions. To enhance their nutrient removal potential, the biochars were chemically modified with magnesium oxide (MgO), allowing for a comparative assessment of unmodified and modified biochars. Batch experiments revealed that unmodified walnut and pistachio biochars did not adsorb phosphorus; instead, they released phosphate into the solution, increasing the concentration by 0.019 mg/g and 0.017 mg/g, respectively. In contrast, MgO‐modified biochar effectively removed phosphorus, with modified walnut biochar demonstrating a maximum phosphorus adsorption capacity of 20.40 mg/g compared to 18.80 mg/g for modified pistachio biochar. For nitrate removal, unmodified biochar performed better, with walnut and pistachio biochars showing adsorption capacities of 6.94 and 5.88 mg/g, respectively. Adsorption behavior was evaluated using the Langmuir and Freundlich isotherms. The Langmuir model generally provided the best fit, except for MgO‐modified pistachio biochar, where the Freundlich model described the data more accurately. This finding provides additional insight into the adsorption process and highlights the contrasting effects of MgO modification on nitrate and phosphorus removal, offering a more accurate model for describing nutrient removal.

ABSTRACT Heavy metal toxicity has become a major threat to living organisms in recent years due to the increase in population and anthropogenic activities. The uptake of lead by the primary producers (plants) is found to affect their metabolic functions, growth, and photosynthetic activity. Globally, various soil amendments have been employed to remediate contaminants in agricultural lands. Soil amendments using food waste could be recognized as cost‐effective, sustainable, and eco‐friendly solutions for “green remediation” strategies. This study aimed to explore how some organic food waste, such as fava, lentil, pea, and soya husk, can adsorb or immobilize the soluble lead (Pb 2+ ) in contaminated soils. Therefore, samples of lead (Pb 2+ ) contaminated soil were amended with and without husk residues and first characterized for their physicochemical properties like porosity, SSA, pH, electrical conductivity, and cation exchange capacity (CEC). Factors influencing heavy metal adsorption, such as initial Pb 2+ concentration, reaction time, and amendment ratio, were assessed. Results showed that the amendments were able to increase porosity, CEC, and electrical conductivity of the soil. Results also indicate that incorporating husks into soil effectively reduces soluble Pb 2+ levels in the soil solution at different concentrations. The adsorption of Pb 2+ in the amended soil follows the Langmuir model, with R 2 of 0.99, while in the non‐amended soil, it follows both the Langmuir (0.87) and the Freundlich (0.88) models. Incorporating 5% of husks is sufficient to achieve Pb 2+ adsorption efficiency of 80%–87%. The controlled and the treated soil samples exhibited a pseudo‐second‐order kinetic model, with high correlation coefficients ( R 2 > 0.99).

ABSTRACT Crude oil pollution poses a significant environmental challenge in oil‐producing regions globally, necessitating research enquiry into sustainable remediation methods. This study explores the isolation of natural silica from Nigerian beach sand, its material characterization, and the optimization of a silica‐based formulation for the remediation of crude oil‐contaminated soil. Silica was isolated using a modified alkali fusion method and characterized with FTIR, SEM–EDX, TGA/DTA, and XRD analyses. The characterization procedure confirmed the presence of high‐purity silica in crystalline form. Laboratory simulation with a 10% (w/w) crude‐oil load increased soil TPH from approximately 708.93 mg/kg (baseline) to approximately 70107.5 mg/kg, representing a nearly hundredfold increase in hydrocarbon content, thus providing a stringent test case for remediation. Optimum treatment conditions (1% silica, 2% sodium dodecyl sulfate, pH 5 and 8, ~25°C) were established through standard optimization procedures. The silica‐based formulation achieved approximately 99% oil removal within 96 h under these conditions, as measured by molecular spectroscopy. Kinetic analysis revealed a zero‐order encapsulation mechanism, with rate constants of approximately 800 mg kg − ¹ h – ¹ and characteristic half‐lives of approximately 44 h at both pH 5 and 8. The results demonstrate that a silica‐based formulation derived from local beach sand can deliver rapid, near‐complete remediation under field‐feasible conditions, highlighting its potential as a scalable and sustainable solution for treating hydrocarbon‐contaminated soils.

ABSTRACT In recent years, many US entities, including the Department of Defense, have initiated hundreds of remedial investigations (RIs) at sites with per‐ and polyfluoroalkyl substance (PFAS) contamination. Although this work generally follows traditional guidance, considerable autonomy is given to the consultant conducting the RI, leading to variable methodologies and associated outcomes, all else equal. Thus, there is a need for a conceptual and systematic framework for conducting an RI for PFAS, especially considering growing knowledge related to the novelty of their fate and transport and ubiquity in the environment. To address this need, at least as it pertains to defining the nature and extent of contamination, we summarize various methods presented to date and recommend a standard of practice that balances trade‐offs between technical rigor and cost as a systematic guide for practitioners consistent with the state of the science.

ABSTRACTMining waste generated during the extraction and processing of minerals in the mining industry represents a social and environmental problem due to the potential impacts associated with the nature of the waste and its toxicity. To mitigate the impact generated by mining waste, this research is an engineering application that seeks to use mining waste sustainably by manufacturing blocks of mining waste. In this article, the physical, mechanical, and chemical properties of blocks manufactured from mine tailings for use as refractory brick in the domestic or construction sector were evaluated to determine their composition and behavior. The mine tailings blocks were subjected to temperatures of 1200°C, resulting in an acid‐type refractory brick, high‐density refractory brick (2.4 g/cm3), with a porosity of 43%, to 24 hardness (474–468 HLD), absorption (28.6%– 5.7%), smooth and homogeneous texture, and resistant to corrosion by acids. The refinery bricks exhibited a mechanical resistance of 50.57–181.66 MPa, flexion resistance of 2.93–13 MPa, and thermal expansion of 0.17 mm. To better understand the textural and chemical characteristics, a detailed study involving field analysis, X‐ray diffraction analysis, X‐ray fluorescence analysis, and morphometric analysis using a petrographic microscope and scanning electron microscopy was carried out. Regarding the chemical composition, the bricks have a high SiO2 content (80.6%) and contents of CaO and Al2O3 of 6.65% and 6.0%, respectively. The mineral phases consist of quartz β, cristobalite, and opal, designating the blocks as acid‐refractory brick. Acid‐refractory bricks obtained from mining tailings represent an option to reduce waste in the environment and provide an alternative as a raw building material in the domestic and industrial sectors.

ABSTRACTThe application of biomaterials in the remediation of contaminated water requires studies that support their use, involving physical, chemical, and/or biological treatments. This study aimed to physicochemically characterize the adsorption process of biomaterials created from orange peels, tamarind seeds, and avocado seeds when they interact with lead to remove it from water. Additionally, we compared the adsorption efficiency between materials subjected to physical processes and chemical processes (polymerized with polyanilines). Our results indicate that orange peel is the best option for Pb(II) concentrations lower than 100 mg L−1, whereas avocado seeds offer better adsorption results for higher concentrations, followed by tamarind seeds. The results show that Freundlich isotherms best describe the adsorption process. The Fourier Transform Infrared spectra indicate that chemisorption is the dominant mechanism. This is supported by comparing the adsorption capacity of the biomaterial with that of the biomaterial polymerized with polyanilines; this process reduces adsorption by up to 40% due to the diminution of active sites. The optimal pH for orange peel and tamarind seeds is 4.5, whereas for avocado it is 6.0, which coincides with the pKa of carboxyl groups. The infrared spectra suggest that the interaction occurs in the carboxyl groups.