This review explores biochar’s potential as a sustainable and cost-effective solution for remediating organic pollutants, particularly polycyclic aromatic hydrocarbons (PAHs) and pesticides, in water. Biochar, a carbon-rich material produced from biomass pyrolysis, has demonstrated adsorption efficiencies exceeding 90% under optimal conditions, depending on the feedstock type, pyrolysis temperature, and functionalization. High surface area (up to 1500 m²/g), porosity, and modifiable surface functional groups make biochar effective in adsorbing a wide range of contaminants, including toxic metals, organic pollutants, and nutrients. Recent advancements in biochar production, such as chemical activation and post-treatment modifications, have enhanced adsorption capacities, with engineered biochar achieving superior performance in treating industrial, municipal, and agricultural effluents. However, scaling up biochar applications from laboratory research to field-scale wastewater treatment poses significant challenges. These include inconsistencies in adsorption performance under variable environmental conditions, the high cost of large-scale biochar production, logistical challenges in handling and deploying biochar at scale, and the need for integration with existing treatment systems. Such challenges impact the practical implementation of biochar-based remediation technologies, requiring further investigation into cost-effective production methods, long-term performance assessments, and field-level optimization strategies. This review underscores the importance of addressing these barriers and highlights biochar’s potential to offer a sustainable, environmentally friendly, and economically viable solution for large-scale wastewater treatment.

This study examines the structural, chemical, and thermal properties of biochars from slow pyrolysis of hardwood (HW), corn cob (CC), and wheat straw (WS) at 400 °C and 700 °C, evaluating their potential in environmental and industrial applications. A combination of spectroscopic, crystallographic, thermal, and microscopic techniques was employed to monitor the degradation of biomass components and the development of the carbonaceous matrix. The results show that pyrolysis temperature has a significant impact on the properties of biochar. Higher temperatures (700 °C) increased the pH (up to 10.3 for WS700), the carbon content (e.g., 89.8% for HW700), the ash content (up to 24.8% for WS700), and the specific surface area (e.g., 306.87 m²/g for CC700) while decreasing polar functional groups and volatile matter (as confirmed by FTIR). SEM showed enhanced porosity at 700 °C, which was supported by BET analysis. XRD and Raman showed increased graphitization and structural order with temperature, especially for HW and CC biochars, while WS biochars retained mineral components like SiO₂ and CaCO₃. TGA analysis showed improved thermal stability at 700 °C only for biochar derived from wheat straw, while HW and CC biochars showed similar total mass loss regardless of pyrolysis temperature. These biochars exhibit high potential for soil remediation (high pH), water purification (large surface area), and carbon storage (high aromaticity), with HW700 and CC700 also suitable for high-temperature industrial applications due to their stability.

Biochar undergoes significant transformations in soil as a result of chemical, physical, and biological processes. These alterations can impact its initial properties, influencing both its agronomic effectiveness and its capacity for carbon sequestration. Long-term observations of biochar-aging effects in soil are limited but highly relevant, as they provide a more realistic picture of the agronomic and societal benefits of biochar than short-term studies with relatively “fresh” biochar. This study aimed to describe the aging effects of biochar and their impact on a range of soil properties at a long-term biochar experiment in Bayreuth, Germany. For this purpose, soil and biochar samples were taken 13 years after application (two variants: 1. co-composted and 2. pristine biochar) and compared with a fresh variant in which the same unaged biochar was freshly mixed with the control soil. The soil quality parameters, pH and electrical conductivity, decreased significantly (p < 0.05) during biochar aging. Specifically, the pH dropped from 7.4 in freshly biochar-amended soil to 6.8 in the pristine aged biochar variant and 6.9 in the co-composted aged biochar variant. Electrical conductivity decreased from 217.0 µS cm⁻¹ in the freshly amended soil to 81.1 µS cm⁻¹ in the pristine aged variant and 87.6 µS cm⁻¹ in the co-composted aged variant. Nitrogen retention was enhanced in the soil amended with co-composted aged biochar compared to the pristine aged biochar soil. Total nitrogen (TN) was higher at 1.94 g kg⁻¹ versus 1.57 g kg⁻¹ (p < 0.05), and ammonium-N (NH₄⁺-N) was slightly elevated at 35.7 mg kg⁻¹ versus 33.0 mg kg⁻¹, although the difference was not statistically significant. The nitrate-N (NO₃⁻-N) content was significantly lower in all biochar-amended soil variants compared to the control soil. Total carbon (TC) levels decreased during biochar aging in all soil variants. However, the reduction was significantly lower in the co-composted aged biochar soil (25.0 g kg⁻¹) compared to the pristine aged biochar soil (20.5 g kg⁻¹, p < 0.05). This study identified multiple aging effects on biochar following 13 years of exposure in loamy soil. Importantly, the results showed that compared to the amendment of pristine biochar, co-composting did not diminish the TC of the treated soil, and more N could be retained, 13 years after amendment. In fact, co-composting prior to soil application is recommended to fully realize the potential agronomic benefits.

Arsenic and heavy metal contamination in water presents serious environmental and public health challenges, requiring effective treatment technologies. Titanium dioxide (TiO₂) nanoparticles offer promising adsorption potential due to their high surface area, mesoporosity, and chemical stability. This study investigates the removal of As(V), Cd(II), Cu(II), and Pb(II) by TiO₂ under environmentally relevant conditions (pH 3 and 7), commonly encountered in industrial and natural waters. TiO₂ was characterized using SEM, XRD, FTIR, BET, and pH_pzc analysis, confirming a mesoporous structure with mixed anatase/rutile phases. Adsorption followed Elovich kinetics, with the Langmuir model providing the best fit to the isotherm data. At pH 3, adsorption capacities (q_m) were of the following order: Pb(II) 30.80 mg g⁻¹ > Cd(II) 10.02 mg g⁻¹ > As(V) 8.45 mg g⁻¹ > Cu(II) 2.73 mg g⁻¹; at pH 7, they were as follows: Cd(II) 26.75 mg g⁻¹ > Pb(II) 26.20 mg g⁻¹ > As(V) 8.50 mg g⁻¹ > Cu(II) 5.05 mg g⁻¹. These results highlight a pH-dependent mechanism involving both chemisorption and physisorption. Principal Component Analysis (PCA) revealed that physicochemical properties, particularly electronegativity, significantly influenced removal efficiency. TiO₂ showed high, selective, and pH-responsive adsorption properties, supporting its use in sustainable water treatment. Future work should address nanoparticle recovery, regeneration, and performance under continuous flow conditions.

This study explores biochar-based catalysts made from hardwood (HW) and wheat straw (WS) biomass for activating persulfate (PS) in the removal of lindane and β-endosulfan from water. The effects of pyrolysis temperature, solution pH, and PS concentration were investigated. The results indicated that both feedstock and pyrolysis temperature are key factors influencing biochar composition. Biochars pyrolyzed at 700 °C exhibited higher surface areas compared to those pyrolyzed at 400 °C, suggesting more effective interactions with the target pesticides. Changes in pH had a minimal impact on pesticide removal, while increasing the PS concentration from 0.5 to 3 mM accelerated degradation. However, further increases in PS concentration slowed the degradation of both pesticides. Under optimal conditions (pH of 7.0 ± 0.2 and PS concentration of 3 mM), the HW700/PS and WS700/PS systems achieved > 90% removal of pesticides within 4 h. Quenching experiments confirmed that non-radical species (¹O₂), generated through persulfate activation by biochar, were the key factor in lindane degradation in both systems, supporting the catalytic role of biochar rather than mere adsorption. In the HW700/PS system, SO₄^•−, HO^•, and ¹O₂ acted synergistically to enhance the degradation of β-endosulfan, whereas in the WS700/PS system, the degradation was mainly driven by SO₄^•− and ¹O₂. Notably, HW700 biochar maintained its activation efficiency during β-endosulfan degradation even after five cycles. This research offers new insights into the potential of biochar-activated PS as a green, cost-effective, and efficient method for water treatment, addressing pesticide-contaminated surface water and promoting agricultural waste recycling.

This work explores the relationship between water quality and public trust in their water supply, in an arsenic-affected region of Serbia. The results from an online public survey are presented and subjected to Pearson’s correlation, cluster analysis, and principal component analysis. In general, survey respondents in settlements with known arsenic issues had a poor opinion on the quality of their tap water. This poor opinion was underlined by their consumption of bottled water, with more than 43% of responders purchasing at least 5 L of bottled water a week. In addition to the great economic cost, the relatively low plastic recycling rate in Serbia means that this also has a very negative effect on the environment, as most of the plastic bottles are sent to landfill, to degrade slowly into microplastics, whilst leaching a variety of chemical contaminants into the surroundings. In the area studied, the poor public opinion of the water quality is a realistic reflection of water at the tap. Although significant, the additional environmental pollution from bottled water consumption should nonetheless be of secondary consideration in comparison to the health risks associated with chemical contaminants in the study area, with local waterworks requiring significant financial assistance if they are to meaningfully improve tap water quality.