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.

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 study investigates the potential of corn cob-derived biochars produced at 400 °C (BC400) and 700 °C (BC700) as heterogeneous catalysts for the degradation of organochlorine pesticides, lindane and β-endosulfan, through persulfate-based advanced oxidation processes (AOPs). BC700 exhibited enhanced degradation performance compared to BC400, likely due to its greater surface area, higher aromaticity, and lower surface polarity. Under optimized conditions (3.0 mM persulfate, pH 7.02, 0.2 g/L biochar), BC700 enabled the removal of up to 94% of β-endosulfan and 82% of lindane within four hours. Quenching experiments suggested different dominant degradation pathways: singlet oxygen (¹O₂) appeared to play a key role in lindane degradation, while β-endosulfan degradation likely involved both radical (SO₄^•−, HO^•) and non-radical mechanisms. Reusability tests indicated that BC700 retained catalytic activity for β-endosulfan across multiple cycles, whereas lindane degradation efficiency decreased, possibly due to surface fouling or catalyst deactivation. Experiments conducted in real surface water highlighted the influence of matrix components, with partial inhibition observed for β-endosulfan and an unexpected improvement in lindane removal. These results point to the promise of high-temperature corn cob biochar as a selective and potentially reusable catalyst for AOPs in water treatment, warranting further investigation into regeneration strategies and matrix-specific effects.

The electrocatalytic properties of anionic dye-based sensors were demonstrated by their strong influence on the oxidation signal of piperine (PIP), a widely used alkaloid usually found in food and pharmaceutical samples. The purpose of this study was to improve recent advancements on the design and sensing ability of modified carbon paste electrode (CPE) prepared by electropolymerization of dyes for PIP determination. The important variables were the choice of dye for electropolymerization and polymer dye film thickness when incorporated onto the CPE surface, which was evaluated using cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) methods. The performance of the two anionic dye-based sensors, poly(murexide)- (PMUX/CPE) and poly(bromocresol green)-modified CPE (PBCG/CPE) was compared and PMUX/CPE proved to have the most favorable electrocatalytic behavior. CV studies revealed that PIP undergoes an irreversible electrooxidation at the PMUX/CPE and exhibits an adsorptive behavior. Consequently, the sensitivity of the PMUX/CPE was greatly improved when polarized at -0.3 V for 60 s due to the higher accumulation ability of PIP at pH 8.0, as determined during the optimization of the square wave adsorptive stripping voltammetric (SW-AdSV) method. Achieved analytical response of PIP found to be linear in the range of 0.067–3.47 µmol L-1 PIP, and a limit of detection was 21 nmol L-1 PIP. Ultimately, the PIP concentration in a black pepper sample was determined using the designed PMUX/CPE and SW-AdSV method, which demonstrated great sensitivity, selectivity, and reproducibility. The obtained results were confirmed by a comparative spectrophotometric method.

The voltammetric characterisation and determination of insecticide flonicamid (N-cyanomethyl-4-(trifluoromethyl)nicotinamide) were performed for the first time using a simple electrochemical sensor, renewable silver-amalgam film electrode (Hg(Ag)FE). During the development of the direct cathodic square wave voltammetric method (SWV) for the determination of flonicamid, a voltammetric behaviour of a target analyte in aqueous Britton-Robinson buffer solution from pH 2.0 to pH 11.98 was examined. In the investigated pH range, the peak which appeared in the potential span between −0.86 V and −1.56 V vs. saturated calomel electrode depending on the applied pH value was chosen for analytical purposes. As optimal pH for the determination of flonicamid, pH 2.5 was selected. Cyclic voltammetric measurements at pH 2.5 confirmed that the electrode reaction mechanism is an irreversible reduction controlled by the diffusion of flonicamid at Hg(Ag)FE. The optimised Hg(Ag)FE-SWV method resulted in good linearity in the concentration range of 1.96–41.2 µg mL⁻¹ while the relative standard deviation of the method was 0.30%. Flonicamid was successfully determined in commercial formulation Teppeki 500 WG® and spiked river water sample by the developed method using the standard addition procedure. The average value of flonicamid amount found in a commercial formulation based on three repetitions was 497.8 ± 0.9 g kg⁻¹, which is in good agreement with the manufacturer’s declaration (500 ± 25 g kg⁻¹) and with comparative high-performance liquid chromatographic measurements with diode array detection where a found average value of flonicamid content was 497.5 ± 11.5 g kg⁻¹. The obtained results also indicate that the developed SWV procedure using Hg(Ag)FE was appropriate for the determination of flonicamid in a spiked river water sample with the recovery of 92.86% and RSD of 6.19%.