Activation of sawdust biochar with water and wastewater treatment residuals for sorption of perfluorooctanesulfonic acid in water

Recent research has found biochar to be a cost-effective adsorbent for removal of perfluoroalkyl substances in water. To promote cleaner production and sustainable waste management, this study explored the potential to produce activated biochars by co-pyrolyzing sawdust with iron-rich biosolids and polyaluminum sludge. The maximum capacity to adsorb perfluorooctanesulfonic acid (PFOS) reached 27.2 mg g-1 with biosolids-activated biochar and 19.2 mg g-1 with aluminum sludge-activated biochar, compared to 6.2 mg g-1 with sawdust biochar. The increased adsorption capacities were attributed to electrostatic interactions between the anionic PFOS and metal functionalities on the biochar surface. In contrast, hydrophobic interaction was the dominant adsorption mechanism of sawdust biochar. The presence of dissolved organic matter at 5-50 mg L-1 was found to inhibit adsorption of PFOS in water, while pH as low as 3.0 and sodium chloride concentrations up to 100 mM enhanced removal of PFOS by all the three adsorbents. In batch adsorption tests at environmentally relevant PFOS dosages and adsorbent dosage of 0.25 g L-1, the biosolids-sawdust biochar and Al sludge-sawdust biochar removed 71.4% and 66.9% of PFOS from drinking water and 77.9% and 87.9% of PFOS from filtrate of sludge digestate, respectively. The biosolids-sawdust biochar additionally removed Fe, although the Al sludge-sawdust biochar released Al into the alkaline drinking water and filtrate. Overall, this study proved co-pyrolyzing sawdust and Fe-rich biosolids to be an effective approach to activate sawdust biochar for enhanced removal of PFOS while recycling wastewater treatment residuals and sawdust.

Machine learning application for predicting key properties of activated carbon produced from lignocellulosic biomass waste with chemical activation

The successful application of gradient boosting regression (GBR) in machine learning to forecast surface area, pore volume, and yield in biomass-derived activated carbon (AC) production underscores its potential for enhancing manufacturing processes. The GBR model, collecting 17 independent variables for two-step activation (2-SA) and 14 for one-step activation (1-SA), demonstrates effectiveness across three datasets-1-SA, 2-SA, and a combined dataset. Notably, in 1-SA, the GBR model yields R2 values of 0.76, 0.90, and 0.83 for TPV, yield, and SSA respectively, and records R2 of 0.90 and 0.91 for yield in 2-SA and combined datasets. The model highlights the significance of the soaking procedure alongside activation temperature in shaping AC properties with 1-SA or 2-SA, illustrating machine learning's potential in optimizing AC production processes.

Reshaping environmental sustainability: Poultry by-products digestate valorization for enhanced biochar performance in methylene blue removal

Anaerobic digestion is a highly effective and innovative method for treating organic waste while simultaneously generating energy. However, the treatment of the resulting digestate remains a challenging endeavor. To address this issue, poultry by-products digestate is used in this study to prepare biochars at two different pyrolysis temperatures (500/600 °C). Despite their potential, the utilization of untreated biochar is restricted due to its inadequate adsorption capacity. Therefore, each biochar was chemically activated using either HNO3 or KOH to synthesize four activated biochars (BC5@KOH, BC6@HNO3, BC5@HNO3, and BC6@HNO3). The aim is to investigate how the nature of chemical activation and pyrolysis temperature influence the adsorption of methylene blue dye. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Raman analysis, and pHpzc determination, were exploited to comprehensively elucidate the structure and composition of both unprocessed and chemically activated biochars. Among the activated biochars, the adsorbent BC5@HNO3 exhibits the highest methylene blue (MB) adsorption capacity, reaching 101.72 mg.g-1 at 298 K under (pH = 2, ads dose = 0.6 g.L-1, shaking time of 20 min, as optimal conditions for MB adsorption. Adsorption data for each adsorbent strongly aligns with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Moreover, the thermodynamic study reveals that the adsorption process was endothermic and spontaneous. The adsorption mechanism of MB dye was explored using various analytical techniques, including FTIR, SEM, PZC, and pH impact assessment. The findings suggest correlations with electrostatic interactions, hydrogen bonding, pore filling, as well as n-π and π-π interactions. Apparently, activated biochars play a crucial role in efficiently removing methylene blue dye, showcasing their potential as environmentally friendly and effective adsorbents.

Nanocomposite from tannery sludge-derived biochar and Zinc oxide nanoparticles for photocatalytic degradation of Bisphenol A toward dual environmental benefits

The growing concern over the presence of pollutants like Bisphenol A (BPA) in water sources has led to the growth of novel treatment technologies for its removal. This research work investigates the development of a novel biochar-metal oxide nanocomposite derived from tannery sludge and Zinc oxide (ZnO) nanoparticles for the photodegradation of BPA. The biochar was obtained by pyrolysis process, followed by impregnation of ZnO nanoparticles using a hydrothermal technique. The critical properties of as-prepared nanocomposite were evaluated by FT-IR, BET surface area, XRD, FE-SEM, HR-TEM, XPS, PL, EPR, and Raman Spectroscopy. In addition, the photocatalytic activity of nanocomposites was evaluated by measuring the degradation of BPA in visible light irradiation. The outcomes revealed that ZnO-loaded chemically activated biochar exhibited higher photocatalytic activity for the degradation of BPA than the pristine and non-chemically activated biochar. At pH 5, 0.2 g/L of photocatalyst dosage, 20 ppm of initial pollutant concentration, and 150 min of contact time, the maximum degradation efficiency of BPA was observed as 94.50 %. Also, nanocomposites showed good stability and reusability, with only a slight decrease in photocatalytic activity after multiple cycles of use. More importantly, the degradation mechanisms of BPA using as-prepared nanocomposites were analyzed in detail, indicating that the observed photocatalytic activity could be attributed to the synergistic effect between the biochar and ZnO, which provided a large surface area for the adsorption of BPA and promoted the generation of reactive oxygen species for its degradation. Overall, this study highlighted the potential of using nanocomposites from tannery sludge-derived biochar and ZnO nanoparticles for the degradation of BPA from polluted water sources using a photocatalytic process toward the dual environmental benefits.

Activated biochar derived from Enteromorpha with high specific surface area for efficient removal of phenanthrene: Experiments, mechanism and DFT calculations

Conversion of solid marine waste into innovative nanomaterials has been successfully developed for removing organic pollutants from aqueous solutions. In this study, activated biochar (HTST) was successfully synthesized using a straightforward three-step method involving pretreatment, carbonization, and chemical regulation. Multiple characterization techniques revealed the presence of abundant three-dimensional hierarchical porous structures in the samples, along with amorphous and active functional group structures such as -COOH, -OH, -NHR, -CC, and C-O. Notably, the prepared sample exhibited a remarkable specific surface area (SBET) of 3284.52 m2/g, which was close to 1700 times larger than that of the raw biomass. Additionally, the highest removal efficiency could reach approximately 100% under neutral condition, while the adsorption capacity even achieved up to 782.37 mg/g within 2 h at room temperature. Calculations simulation not only highlighted the significance of the π-π conjugation between sample and pollutant molecules, but deeply explored the bonding interaction of active functional groups on the surface, whereas adsorption energies of different configurations had the following order: ΔE(-NHR) = 0.75194674 eV > ΔE(-OH) = 0.72502369 > ΔE(-COOH) = 0.71488135 > ΔE(-CC-) = 0.53852269 eV. Moreover, the adsorption activities for the optimized configuration were further analyzed based on the LUMO-HOMO energy gap and electric distribution. This work presents a viable synthesis method for low-cost nanomaterials and offers new insights into the exceptional adsorption properties of advanced adsorbents for wastewater treatment.

Effectiveness of biochar as an adsorbent for pesticides: Systematic review and meta-analysis

The use of pesticides is intense in agriculture and has caused contamination in water, air and soil. This fact led to the need to study strategies that can minimize the effects that these pesticides have caused to the environment. In this context, biochar appears, as a type of material that has the ability to remove chemical substances, and because they can be activated with different chemical agents, they are extremely effective in the adsorption of toxic substances. Therefore, the aim of the study was to evaluate the use of biochar as a bioadsorbent for pesticides. This is a systematic review with meta-analysis and meta-regression, as the PRISMA protocol recommendations. Studies from the last 20 years were included, with at least the abstract available and considering preferentially experimental studies. Qualitative studies or studies with high risk of bias, other reviews and duplicates were excluded. The variables analyzed were the presence of factors that prove the effectiveness or not of pesticide adsorption. Studies with a superficial approach or those that do not show positivity or negativity in relation to the outcome were excluded. The search was conducted on the sources: Scopus, Web of Science electronic databases, PubMed (of the US National Library of Medicine, National Institutes of Health) and ScienceDirect (Elsevier). For better investigative determination, the data were searched separately. The descriptors used for the search were the following: Agrochemicals AND Activated Carbon AND Adsorption. Initially, 2431 references were found, from which 14 were selected to compose the meta-analysis review. With the joint analysis of the data, it was possible to verify using the random model (since the studies assess different contexts) that there is a proportion of effectiveness of the intervention of 81% (with a 95% confidence interval), ranging from 75 to 88%, which is represented by the meta-analysis diamond that is the final result of the statistical analysis. Biochar is effective in removing impurities, even including features such as low cost. There is a considerable lack of studies on the topic of pesticide adsorption with the use of biochar. The studies approach a very heterogeneous perspective on the subject, exposing different contexts.

Phosphorus adsorption using chemical and metal chloride activated biochars: Isotherms, kinetics and mechanism study

Efficient treatment of nutrient-rich wastewater is of paramount importance for protecting the ecosystem. In this work, an efficient, abundant, and eco-friendly adsorbent was derived from biochar and employed for phosphorus (P) adsorption. The key factors influencing the P removal efficiency of the activated biochar, including P concentration, pH, dosage, temperature, adsorption time, and influence of co-existing ion type, were investigated. Maximum P adsorption percentage (100%) was obtained with 10 mg/L and zinc chloride activated biochar (BC-Zn) compared to the other activated biochars. Results show that by increasing the P concentration from 5 to 200 mg/L, the phosphorus adsorption capacity increases from 0.13 to 10.4 mg/g biochar. Isotherms and kinetic studies further show that the P adsorption follows the Langmuir and quasi-second-order kinetic models. The mechanistic investigation demonstrated that P adsorption occurred by precipitation reaction. Furthermore, P desorption has been studied at different time intervals to understand the P release rate after adsorption.

Electrochemical monitoring of congo red degradation using strontium titanate-doped biochar nanohybrids derived photocatalytic plates

Present investigation demonstrates the development and characterization of strontium titanate (SrTiO₃) doped biochar nanohybrid photocatalysts. Biochar nanohybrid was synthesized using an ultrasonic-assisted dispersion technique, which involved dispersing SrTiO₃ nanoparticles into activated biochar at a weight ratio of 1:2 (w/w) under ambient conditions. The development of the biochar nanohybrid was verified through a comprehensive analysis of their spectral, microstructural, thermal, electrical, and electrochemical properties. The scanning electron microscopy analysis reveals a surface-associated multiphase morphology of the biochar nanohybrid, attributed to the uniform distribution of SrTiO₃ within the activated biochar matrix. Biochar nanohybrid exhibited a reduced optical band gap of 2.77 eV, accompanied by a crystallite size of 32.45. Thermogravimetric analysis revealed the thermal stability of the biochar nanohybrid, as evidenced by a char residue of 70.83% at 1000 °C. The working electrodes derived from biochar nanohybrid have exhibited ohmic behavior and displayed a significantly enhanced DC conductivity (mS/cm) of 1.13, surpassing that of activated biochar (0.53) and SrTiO₃ (0.62) at 100 V. The developed biochar nanohybrid were employed for the degradation of congo red dye by exposing the dye solution to photocatalytic plates. These photocatalytic plates were prepared by coating biochar nanohybrid onto glass plates using epoxy-based reactive binders for secure binding. The photodegradation of congo red was evaluated through cyclic voltammetric analysis in a 0.1 M KCl solution at pH 8.0, resulting in an impressive 99.95% photocatalytic efficiency in degrading a congo red solution (50 mg/L). This study presents a novel approach for the fabrication of biochar nanohybrid-derived photocatalytic plates, offering high photocatalytic efficiency for the degradation of congo red dye.

Biosorption of aqueous Pb(II) by H3PO4-activated biochar prepared from palm kernel shells (PKS)

The conversion of palm kernel shells (PKS), a major agricultural waste from the palm oil sector, into a potentially high-value biosorbent for heavy metals-contaminated wastewater treatments was explored in this work. Following carbonization, the activated PKS was chemically activated by soaking the biochar in a phosphoric acid (H3PO4) solution at 25 °C. The low-temperature approach benefits from less dangerous acid fume production and operational challenges when compared to the high-temperature procedure. The properties of the biochar were characterized by BET, FTIR, and SEM. The effects of H3PO4 dosage, initial Pb(II) concentration, and adsorbent dosage on removing Pb(II) from synthetic wastewater were investigated in the adsorption study. The activation of PKS biochar with high H3PO4 concentrations led to enhanced removal efficiency. The pseudo-second-order (PSO) kinetic model fitted the experimental data well (R2 0.99), indicating that chemisorption was likely involved in the adsorption of Pb(II) onto activated PKS. Pb(II) sorption was possibly promoted by the presence of phosphate moieties on the adsorbent surface. The Langmuir isotherm best described the sorption of Pb(II) onto the activated PKS (R2 0.97), giving the calculated maximum adsorption capacity (qm) of 171.1 μg/g. In addition to physical sorption, possible adsorption mechanisms included functional group complexation and surface precipitation. Overall, activating PKS biochar with H3PO4 at room temperature could be a promising technique to improve the adsorbent's adsorption efficiency for Pb(II) removal from wastewater.

Removal of NO at low concentration from air in urban built environments by activated miscanthus biochar

This work presents an innovative and sustainable approach to remove NO emissions from urban ambient air in confined areas (underground parking areas or tunnels) using low-cost activated carbons obtained from Miscanthus biochar (MSP700) by physical activation (with CO₂ or steam) at temperatures ranging from 800 to 900 °C. The NO removal capacity of the activated biochars was evaluated under different conditions (temperature, humidity and oxygen concentration) and compared against a commercial activated carbon. This last material showed a clear dependence on oxygen concentration and temperature, exhibiting a maximum capacity of 72.6% in air at 20 °C, whilst, its capacity notably decreased at higher temperatures, revealing that physical NO adsorption is the limiting step for the commercial sample that presents limited oxygen surface functionalities. In contrast, MSP700-activated biochars reached nearly complete NO removal (99.9%) at all tested temperatures in air ambient. Those MSP700-derived carbons only required low oxygen concentration (4 vol%) in the gas stream to achieve the full NO removal at 20 °C. Moreover, they also showed an excellent performance in the presence of H₂O, reaching NO removal higher than 96%. This remarkable activity results from the abundance of basic oxygenated surface groups, which act as active sites for NO/O₂ adsorption, along with the presence of a homogeneous microporosity of 6 Å, which enables intimate contact between NO and O₂. These features promote the oxidation of NO to NO₂, which is further retained over the carbon surface. Therefore, the activated biochars studied here could be considered promising materials for the efficient removal of NO at low concentrations from air at moderate temperatures, thus closely approaching real-life conditions in confined spaces.

Synthesis and performance of a cathode catalyst derived from Bauhinia accuminata seed pods in single and stacked microbial fuel cell

The cathode catalyst in microbial fuel cell (MFC) plays a crucial role in scaling up. Activity of biomass-derived activated carbon catalysts with appropriate precursor selection in a natural clay membrane-based MFC of 250 mL was studied. The performance of scaled up MFC of 1.5 L capacity with two different configurations was monitored. Rod-shaped particles with slit-type pores and amorphous graphitic nature with a surface area of 800.37 m²/g was synthesized. The intrinsic doping of heteroatoms N and P in the catalyst was with atomic weight percentages of 4.5 and 3.5, respectively and the deconvolution of N1 spectra confirmed pyridinic N and graphitic N content of 17.3% and 34.1% validating its suitability as a cathode catalyst. Electrochemical characterization of the catalyst coated SS mesh electrode confirmed that a loading of 5 mg/cm² rendered higher catalytic activity compared to bare SS mesh. The maximum power density in catalyst modified cell was 0.91 W/m³ compared to 0.02 W/m³ as obtained in a plain stainless steel electrode cell at a COD removal efficiency of 93.3%. Series, parallel, and parallel-series combinations of 6 cells showed a maximum voltage of 4.15 V when connected in series and a maximum power density of 1.54 W/m³ when connected in parallel. System with multielectrode assembly achieved better power and current density (0.84 W/m³ and 1.97 A/m³) than the mixed parallel series circuitry (0.7 W/m³ and 0.57 A/m³). These performance results confirm that the catalyst is effective in both stacked and hydraulically connected system.

The production of activated biochar using Calophyllum inophyllum waste biomass and use as an adsorbent for removal of diuron from the water in batch and fixed bed column

The Calophyllum inophyllum species annually produces a large volume of cylindrical fruits, which accumulate on the soil because they do not have nutritional value. This study sought to enable the use of this biomass by producing activated biochar with zinc chloride as an activating agent for further application as an adsorbent in batch and fixed bed columns. Different methodologies were used to characterize the precursor and the pyrolyzed material. Morphological changes were observed with the emergence of new spaces. The carbonaceous material had a surface area of 468 m² g^-1, D_p = 2.7 nm, and V_T = 3.155 × 10^-1 cm³ g^-1. Scientific and isothermal studies of the adsorption of the diuron were conducted at the natural pH of the solution and adsorbent dosage of 0.75 g L^-1. The kinetic curves showed a good fit to the Avrami fractional order model, with equilibrium reached after 150 min, regardless of the diuron concentration. The Liu heterogeneous surface model well represented the isothermal curves. By raising the temperature, adsorption was encouraged, and at 318 K, the Liu Q_max was reached at 250.1 mg g^-1. Based on the Liu equilibrium constant, the nonlinear van't Hoff equation was employed, and the ΔG° were < 0 from 298 to 328 K; the process was exothermic nature (ΔH⁰ = -46.40 kJ mol^-1). Finally, the carbonaceous adsorbent showed good removal performance (63.45%) compared to a mixture containing different herbicides used to control weeds. The stoichiometric column capacity (q_eq) was 13.30 and 16.61 mg g^-1 for concentrations of 100 and 200 mg L^-1, respectively. The length of the mass transfer zone was 5.326 cm (100 mg L^-1) and 4.946 cm (200 mg L^-1). This makes employing the leftover fruits of the Calophyllum inophyllum species as biomass for creating highly porous adsorbents a very effective and promising option.

Evaluation of digestate-derived biochar to alleviate ammonia inhibition during long-term anaerobic digestion of food waste

The feasibility of using food waste anaerobic digestate-derived biochar (FWDB) to mitigate ammonia toxicity in an anaerobic digester was evaluated. The optimal conditions for preparing and adding the activated FWDB were explored using response surface experiments, and the long-term effects of adding activated FWDB on digester performance under optimum conditions were verified in semi-continuous experiments. The results showed that the optimal preparation and addition conditions for activated FWDB were pyrolysis temperature of 565 °C, particle size of 0-0.30 mm, and dosage of 15.52 g·L-1. During the long-term operation of the digesters, when the total ammonia nitrogen (TAN) concentration was higher than 2000 mg·L-1, the control and experimental digesters showed deteriorated reactor performance. Volatile fatty acids in the control digester accumulated to 20,306 mg·L-1 after the TAN concentration increased to 3391 mg·L-1, the methane yield decreased to 31 mL·g VS-1, and the digester experienced process failure. In contrast, the experimental digester with added activated FWDB only suffered a slight short-term accumulation of acetate and a slight decline in methane yield. This may be attributed to the adsorption of NH4+/NH3 by activated FWDB, which reduced the TAN concentration in the anaerobic digestion (AD) system and mitigated ammonia toxicity. Microbial analysis and metagenome predictions demonstrated that the community richness, diversity, and evenness, as well as the abundance of acetogens and related key genes (ACSM1, paaF, and acdA) were higher in the experimental digester than in the control digester. This study provides a closed-loop AD enhancement strategy by pyrolysis of digestate and in-situ supplementation into the digester.

Adsorption performance and mechanism of cationic and anionic dyes by KOH activated biochar derived from medical waste pyrolysis

The massive generation of medical waste (MW) results in a series of environmental, social, and ecological problems. Pyrolysis is one such approach that has attracted more attention because of the production of value-added products with lesser environmental risk. In this study, the activated biochar (ABC600) was obtained from MW pyrolysis and activated with KOH. The adsorption mechanism of activated biochar on cationic (methylene blue) and anionic (reactive yellow) dyes were studied. The physicochemical characterization of biochar showed that increasing pyrolysis temperature and KOH activation resulted in increased surface area, a rough surface with a clear porous structure, and sufficient functional groups. MB and RYD-145 adsorption on ABC600 was more consistent with Langmuir isotherm (R² ≥ 0.996) and pseudo-second-order kinetics (R² ≥ 0.998), indicating chemisorption with monolayer characteristics. The Langmuir model fitting demonstrated that MB and RYD-145 had maximum uptake capacities of 922.2 and 343.4 mg⋅g^-1. The thermodynamics study of both dyes showed a positive change in enthalpy (ΔH°) and entropy (ΔS°), revealing the endothermic adsorption behavior and randomness in dye molecule arrangement on activated-biochar/solution surface. The activated biochar has excellent adsorption potential for cationic and anionic dyes; hence, it can be considered an economical and efficient adsorbent.

Production of highly porous biochar via microwave physiochemical activation for dechlorination in water treatment

Most biomass is composted into low-grade biofertilizer or processed into energy fuel for burning. At the same time, waste palm shell is potentially converted into highly porous biochar for dechlorination in water treatment. A single-mode microwave activation was developed to perform microwave activation that incorporated the application of steam, KOH, and a physiochemical process. The single-mode microwave activation was performed at the activation temperature ranging from 550-600 °C and recorded a short process duration of 5 min. The steam-activated biochar showed a mass yield of 88.3 wt%, a surface area of 527.4 m²/g, and a dechlorination efficiency of 25.5 mg/g. KOH-activated biochar showed a mass yield of 90.5 wt%, a surface area of 301.1 m²/g and a dechlorination efficiency of 24.0 mg/g. The physiochemical activated biochar showed the highest pores surface area of 717.8 m²/g and dechlorination efficiency of 35.8 mg/g but the lowest mass yield of 77.6 wt%. The results demonstrate that the greater the surface area, the higher the dechlorination efficiency. Using microwave heating and physiochemical activation technology demonstrates a promising way to produce activated biochar for the dechlorination of drinking water.

Oxidation of sulfamethazine by peracetic acid activated with biochar: Reactive oxygen species contribution and toxicity change

Peracetic acid (PAA) as an emerging oxidative has been concerned increasingly due to its high oxidation capacity and low byproducts formation potential. This study was to investigate the oxidation of sulfamethazine (SMZ) by PAA activated with activated biochar (ABC) after thermal modification. The results demonstrated that PAA could be effectively activated by ABC to degrade SMZ in a wide pH range (3-9), which followed the pseudo-second-order kinetics (R² > 0.99). Both non-radicals (singlet oxygen) and free radicals (alkoxy radicals, hydroxyl radicals) existed in the ABC/PAA system, and the degradation of SMZ was dominated by singlet oxygen. Humic acid (HA), SO₄^2- and HCO₃^- slightly inhibited the degradation of SMZ in the ABC/PAA process, while Cl^- and Br^- promoted the degradation of SMZ. The cleavage of S-N, S-C bond, and SO₂ extraction reaction rearrangement was the main oxidation process of SMZ. Meanwhile, the results of the ECOSAR program showed that the acute toxicity of most by-products was significantly reduced compared to SMZ, which revealed the potential applicability of the ABC/PAA process in the treatment of antibiotics pollution and their detoxification.

Visible-light-driven photocatalytic degradation of dye and antibiotics by activated biochar composited with K+ doped g-C3N4: Effects, mechanisms, actual wastewater treatment and disinfection

To improve the performance of graphitic carbon nitride (g-C₃N₄), a hotly researched metal-free photocatalyst, for better application in the efficient removal of organic pollutants, adsorption synergistically enhanced photocatalysis mechanism was thoroughly explored. Based on KOH pore-forming activated biochar (ACB) and K⁺ doped g-C₃N₄ (K-gC₃N₄), the novel activated biochar-based K-gC₃N₄ composite (ACB-K-gC₃N₄) was synthesized via the innovative ultrasonic-milling method. Rhodamine B (RhB), tetracycline (TC), norfloxacin (NOR), and chloramphenicol (CAP) were selected as target pollutants, and the effects of environmental factors, recycling and actual wastewater tests, disinfection effects, and various enhancement strategies were investigated. The results showed that K-gC₃N₄ was successfully composited with ACB by various characterizations, where the loading mass ratio of 1:2 exhibited the best performance. ACB-K-gC₃N₄ possessed a larger specific surface area, richer functional groups, suitable band gap (2.29 eV), and broader visible light absorption (~716 nm) than K-gC₃N₄. ACB-K-gC₃N₄ presented effective removal efficiency over K-gC₃N₄ for four pollutants, in which the removal efficiency of RhB reached 93.26%, and the degradation rate constant of 0.0119 min^-1 was four times higher than K-gC₃N₄ (0.0029 min^-1). Moreover, ACB-K-gC₃N₄ was superior to K-gC₃N₄ in disinfecting S. aureus and E. coli, with a sterilization rate of exceeding 90% for 12 h. The photodegradation activity was dominated by ·O₂^-, h⁺, and ·OH, and the mechanisms involved in the three stages. This was attributed to the unique structure and surface properties (defects and persistent free radicals) of ACB, as evidenced by improved adsorption stage and transfer of degradation intermediates, facilitated the generation of active species, accelerated migration of photogenerated electrons, and inhibited photogenerated carriers recombination by the heterojunction. The good reusability and stability, enhancement strategies (blowing air and heating), and satisfactory feasibility for actual wastewater allow ACB-K-gC₃N₄ possible to promote high-concentration wastewater treatment and disinfection.

Shrimp waste-derived porous carbon adsorbent: Performance, mechanism, and application of machine learning

Aquaculture generates significant amount of processing wastes (more than 500 million pounds annually in the United States), the bulk of which ends up in the environment or is used in animal feed. Proper utilization of shrimp waste can increase their economic value and divert them from landfills. In this study, shrimp waste was converted to a porous carbon (named SPC) via direct pyrolysis and activation. SPC was characterized, and its performance for adsorbing ciprofloxacin from simulated water, natural waters, and wastewater was benchmarked against a commercial powdered activated carbon (PAC). The surface area of SPC (2262 m²/g) exceeded that of PAC (984 m²/g) due to abundance of micropores and mesopores. The adsorption of ciprofloxacin by SPC was thermodynamically spontaneous (ΔG = -19 kJ/mol) and fast (k₁ = 1.05/min) at 25 °C. The capacity of SPC for ciprofloxacin (442 mg/g) was higher than that of PAC (181 mg/g). SPC also efficiently and simultaneously removed low concentrations (200 µg/L) of ciprofloxacin, long-chain per- and polyfluoroalkyl substances (PFAS), and Cu ions from water. An artificial neural network function was derived to predict ciprofloxacin adsorption and identify the relative contribution of each input parameter. This study demonstrates a sustainable and commercially viable pathway to reuse shrimp processing wastes.

Fabrication and characterization of a novel Ba2+-loaded sawdust biochar doped with iron oxide for the super-adsorption of SO42- from wastewater

Biochar is a low-cost adsorbent used in the treatment of contaminated wastewater. We investigated the potential of an Fe-impregnated, Ba²⁺-loaded biochar (Fe-(Ba-BC)) for the removal of SO₄^2- from aqueous solutions. The Ba²⁺-loaded biochar was synthesized from sawdust impregnated with iron oxide via pyrolysis at 600 °C. The porous structure of the Fe-(Ba-BC) was identified by scanning electron microscopy before sulfate was adsorbed onto the adsorbent. Functional groups were determined by energy-dispersive spectrophotometry and Raman spectrometry.. The Fe-(Ba-BC) Raman peaks before the experiment were higher than after, suggesting the precipitation of BaSO₄. The presence of BaCl₂ on the surface of the biochar was confirmed by X-ray diffraction. Batch sorption results showed that Fe-(Ba-BC) strongly adsorbed aqueous SO₄^2- with a removal efficacy of 96.7% under the optimum conditions of 0.25 M BaCl₂, a contact time of 480 min, a pH of 9 and an adsorbent dose of 2 g. The optimum condition for removal and reaction rate kinetics analysis indicated that adsorption curve fitted well with PSO, k₂ 0.00015 confirmed the removal of SO₄^2- via chemisorption. Thus, Fe-(Ba-BC) was found to be a favorable adsorbent for removing SO₄^2-.

Development and application of a predictive model for advanced wastewater treatment by adsorption onto powdered activated carbon

This work presents a mathematical method to describe adsorptive removal of organic micropollutants (OMPs) and dissolved organic carbon (DOC) from wastewater treatment plant effluent using powdered activated carbon (PAC). The developed model is based on the tracer model (TRM) as a modification of the ideal adsorbed solution theory (IAST) and uses the fictive component approach for organic matter fractionation. It enables the simulation of multisolute adsorption of OMPs considering competitive adsorption behavior of organic background compounds (OBC). Adsorption equilibrium data for DOC and seven different OMPs as well as kinetic data for DOC were derived from batch experiments performed with secondary clarifier effluent of two municipal wastewater treatment plants (WWTP 1 and WWTP 2). Two conventional PAC products were investigated as well as one biogenic PAC (BioPAC). Verification and validation of the fitting results based on operational data of WWTP 1 showed promising prediction of DOC and OMP removal efficiency. However, when applied to a static simulation of a full-scale PAC adsorption stage, the model overpredicts the removal efficiency of sulfamethoxazole and candesartan. For benzotriazole, carbamazepine or hydrochlorothiazide, predicted removal falls below operational removal. The model can be used to predict removals of good adsorbable OMPs but fails to accurately predict the removals of OMPs with variable or low PAC affinity. The model was further used for a dynamic simulation of DOC and diclofenac effluent concentrations of a full-scale PAC adsorption stage with varying operating conditions and influent concentrations. Results show that the hydraulic retention time (HRT) in the contact reactor is a decisive operational parameter for OMP removal efficiency besides the PAC dose.

Use of methanotrophically activated biochar in novel biogeochemical cover system for carbon sequestration: Microbial characterization

Biochar-amended soils have been explored to enhance microbial methane (CH₄) oxidation in landfill cover systems. Recently, research priorities have expanded to include the mitigation of other components of landfill gas such as carbon dioxide (CO₂) and hydrogen sulfide (H₂S) along with CH₄. In this study, column tests were performed to simulate the newly proposed biogeochemical cover systems, which incorporate biochar-amended soil for CH₄ oxidation and basic oxygen furnace (BOF) slag for CO₂ and H₂S mitigation, to evaluate the effect of cover configuration on microbial CH₄ oxidation and community composition. Biogeochemical covers included a biochar-amended soil (10% w/w), and methanotroph-enriched activated biochar amended soil (5% or 10% w/w) as a biocover layer or CH₄ oxidation layer. The primary outcome measures of interest were CH₄ oxidation rates and the structure and abundance of methane-oxidation bacteria in the covers. All column reactors were active in CH₄ oxidation, but columns containing activated biochar-amended soils had higher CH₄ oxidation rates (133 to 143 μg CH₄ g^-1 day^-1) than those containing non-activated biochar-amended soil (50 μg CH₄ g^-1 day^-1) and no-biochar soil or control soil (43 μg CH₄ g^-1 day^-1). All treatments showed significant increases in the relative abundance of methanotrophs from an average relative abundance of 5.6% before incubation to a maximum of 45% following incubation. In activated biochar, the abundance of Type II methanotrophs, primarily Methylocystis and Methylosinus, was greater than that of Type I methanotrophs (Methylobacter) due to which activated biochar-amended soils also showed higher abundance of Type II methanotrophs. Overall, biogeochemical cover profiles showed promising potential for CH₄ oxidation without any adverse effect on microbial community composition and methane oxidation. Biochar activation led to an alteration of the dominant methanotrophic communities and increased CH₄ oxidation.

Statistical evaluation of cow-dung derived activated biochar for phenol adsorption: Adsorption isotherms, kinetics, and thermodynamic studies

Sustainable and economical wastewater treatment forms a vital step towards long-term sustainability of petrochemical refineries and industries. An affordable solution to this challenge is to employ biowaste as the key consumable active component. This paper describes the synthesis and characterization of activated biochar derived from cow-dung, a readily available raw material in low-resource settings, and its application for adsorption of phenol, one of the major pollutants in industrial wastewater. Adsorption parameters are optimized by using response surface methodology. Phenol adsorption equilibrium and kinetics data are well fitted to Freundlich isotherm (R² = 0.97) and pseudo-second-order model (R² = 0.99), respectively. The maximal adsorption capacity (518.89 mg/g) was attained using the Langmuir isotherm model at pH 6.0. Negative values of thermodynamic parameters confirmed the spontaneity, feasibility, and exothermic behaviour of adsorption reaction. The results demonstrate that synthesized activated biochar showed an excellent phenol adsorption capacity of 98.8 %.

Evaluation of oil palm fiber biochar and activated biochar for sulphur dioxide adsorption

The emission of sulphur dioxide (SO₂) gas from power plants and factories to the atmosphere has been an environmental challenge globally. Thus, there is a great interest to control the SO2 gas emission economically and effectively. This study aims to use and convert abundantly available oil palm fiber (OPF) biomass into an adsorbent to adsorb SO₂ gas. The preparation of OPF biochar and activated biochar was optimised using the Response Surface Methodology (RSM) based on selected parameters (i.e., pyrolysis temperature, heating rate, holding time, activation temperature, activation time and CO₂ flowrate). The best adsorbent was found to be the OPF activated biochar (OPFAB) compared to OPF biochar. OPFAB prepared at 753 °C for 73 min of activation time with 497 ml/min of CO₂ flow yields the best adsorption capacity (33.09 mg/g) of SO₂. Meanwhile, OPF pyrolysed at 450 °C of heating temperature, 12 °C/min of heating rate and 98 min of holding time yield adsorption capacity at 18.62 mg/g. Various characterisations were performed to investigate the properties and mechanism of the SO₂ adsorption process. Thermal regeneration shows the possibilities for the spent adsorbent to be recycled. The findings imply OPFAB as a promising adsorbent for SO₂ adsorption.

Biosorbent derived from coffee husk for efficient removal of toxic heavy metals from wastewater

In this study, we investigated the feasibility on the utilization of coffee husk as biosorbents for the removal of heavy metal ions such as Pb²⁺ and Cd²⁺ from wastewater. Biochar was produced from coffee wastes and modified with sodium hydroxide to create functional groups on the surface and increase the specificic surface area. The resultant products were characterized by using various analytical methods such as scanning electron microscopy, specific area, surface functional group and zeta potential analysis. The as-prepared materials were employed as adsorbent to remove Pb²⁺ and Cd²⁺ ions from wastewater. The maximum sorption capacities of biosorbents were measured to be 116.3 and 139.5 mg g^-1 for Cd²⁺ and Pb²⁺, respectively, which is comparable to the conventional adsorbents. Kinetic studies showed that the sorption of Pb²⁺ and Cd²⁺ on biosorbents can be described by the Freundlich isotherm and second-order kinetic model. The coffee husk-derived biosorbent was capable of removing 89.6% of Pb²⁺ and 81.5% Cd²⁺ ions from wastewater, and therefore can be considered as low-cost and efficient adsorbent to remove heavy metal ions from wastewater.

Enhancement of plasticizer adsorption by utilizing a rice bran-derived adsorbent

Bis(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) are commonly used plasticizers in many countries and are detected at significant levels in the environment. Wastewater treatment plants are currently unable to completely treat wastewater discharges containing plasticizers. Rice bran was used to prepare magnetic-activated biochar (MAB) as a reusable adsorbent for enhanced adsorption of DEHP and DBP. The influence of the adsorbent dose, temperature, and adsorption time on the removal efficiency of MAB was studied using response surface methodology (RSM). An analysis of the results indicated that the optimum conditions were a MAB dose of 3.6 g/L, a temperature of 49 °C, and an adsorption time of 454 min for DEHP removal; and a MAB dose of 3.7 g/L, a temperature of 36 °C and an adsorption time of 312 min for DBP removal. The adsorption isotherm data were well fitted by the Langmuir isotherm model, and the adsorption kinetic data were reasonably described by the pseudosecond-order model. MAB is a potential adsorbent for DEHP and DBP removal because of good removal efficiency and reusability.

Adsorption and regeneration on iron-activated biochar for removal of microcystin-LR

Novel iron activated biochars (FA-BCs) were prepared via simultaneous pyrolysis and activation of FeCl₃-pretreated bermudagrass (BG) for removing microcystin-LR (MC-LR) in aqueous solution. Compared to the raw BC (without activation), the surface area and adsorption capacity of FA-BC at iron impregnation ratio of 2 (2 g FeCl₃/g BG) were enhanced from 86 m²/g and 0.76 mg/g to 835 m²/g and 9.00 mg/g. Moreover, FA-BC possessed various iron oxides at its surface which provided the catalytic capacity for regeneration of MC-LR spent FA-BC and magnetic separation after the MC-LR adsorption. Possible mechanisms for the MC-LR adsorption onto FA-BC would include electrostatic attraction, π⁺-π, hydrogen bond, and hydrophobic interactions. The detailed adsorption studies indicated mainly chemisorption and intra-particle diffusion limitation would participate in the adsorption process. The thermal regeneration at 300 °C kept high regeneration efficiency (99-100%) for the MC-LR spent FA-BC during four cycles of adsorption-regeneration. In addition, the high regeneration efficiency (close to 100%) was also achieved by persulfate oxidation-driven regeneration. FA-BC also exhibited high adsorption capacity for the MC-LR from the real lake water to meet the MC-LR concentration below 1 μg/L as a safe guideline suggested by WHO.

Stabilization of PFAS-contaminated soil with activated biochar

Biochars are considered potential sustainable sorbents to reduce the leaching of per- and polyfluoroalkyl substances (PFAS) from contaminated soils. However, biochar characteristics must probably be optimized to achieve useful sorption capacity. In the present work, eight waste timber biochars were produced, including biochars activated to different degrees, at different temperatures, and using both steam and CO₂. In laboratory batch experiments, the eight biochars were amended to soil samples from two different horizons, with low and high total organic carbon (TOC, 1.6% and 34.2%, respectively), of a heavily PFAS-contaminated soil (1200-3800 μg kg^-1 PFAS_tot), at varying doses (0, 0.1, 0.5, 1.0 and 5.0%). With a 5% amendment to the low-TOC soil, all eight biochars resulted in strongly reduced leachate PFAS concentrations (by 98-100%). At the same amendment dose in the high-TOC soil, leachate concentration reductions were more modest (23-100%). This was likely due to a strong PFAS-sorption to the high-TOC soil itself, as well as biochar pore clogging in the presence of abundant organic matter, resulting in fewer sorption sites available to PFAS. Reduction in PFAS leaching was proportional to the degree of activation and activation temperature. Thus, lower amendment doses of activated biochars were needed to reduce PFAS leaching to the same level as with the non-activated biochar. Activation however, came at a tradeoff with biochar yield. Furthermore, the adsorption ability of these biochars increased proportionally with PFAS-fluorocarbon chain length, demonstrating the role of hydrophobic interactions in reduction of PFAS leaching. Development of internal surface area and porosity was proposed as the main factor causing the improved performance of activated biochars. This study shows that woody residues such as waste timber can be used to produce effective sorbents for the remediation of PFAS-contaminated soil. It also highlights the desirability of sorbate and matrix-specific optimization of biochar production.

A new biochar from cotton stalks for As (V) removal from aqueous solutions: its improvement with H3PO4 and KOH

The present study is the first attempt to evaluate the potential of acid and base activated biochar derived from cotton stalks (CSB) for the removal of As from contaminated water. The CSB was treated with 0.5 M KOH (BCSB) and H₃PO₄ (ACSB) separately to change its surface properties. The CSB, ACSB and BSCB were characterized using BET, FTIR, and SEM analysis to check the effectiveness and insight of the main mechanisms involved in the removal of As. A series of batch experiments was performed using As-contaminated synthetic water and groundwater samples. The effects of initial concentration of As, contact time, dose of the biochars, solution pH, type of the biochar and coexisting ions on the removal of As were investigated. Results revealed that BCSB efficiently removed As (90-99.5%) from contaminated water as compared with ACSB (84-98%) and CSB (81-98%) due to improved surface properties when As concentration was varied from 0.1 to 4.0 mg/L. The experimental data were best fitted with Freundlich adsorption isotherm as compared with Langmuir, Temkin and Dubinin-Radushkevich models. However, kinetic data were well explained with pseudo-second-order kinetic model rather than pseudo-first-order, intra-particle diffusion and Elovich models. The sorption energy indicated that physical adsorption was involved in the removal of As. The comparison of adsorption results with other biochars and their modified forms suggests that activation of CSB with base can be used effectively (4.48 mg/g) as a low-cost adsorbent for maximum removal of As from contaminated aqueous systems.

Extraction of active pharmaceutical ingredients from simulated spent activated carbonaceous adsorbents

Activated carbon (AC) and activated biochar (ABC) are widely used as sorbents for micropollutant removal during water and wastewater treatment. Spent adsorbents can be treated in several ways, e.g., by incineration, disposal in landfills, or reactivation. Regeneration is an attractive and potentially more economically viable alternative to modern post-treatment practices. Current strategies for assessing the performance of regeneration techniques often involve only repeated adsorption and regeneration cycles, and rarely involve direct measurements of micropollutants remaining on the adsorbent after regeneration. However, the use of regenerated adsorbents containing such residual micropollutants could present an environmental risk. In this study, the extraction of eight active pharmaceutical ingredients (APIs) commonly found in treated effluents was evaluated using 10 solvents and sorption onto three different carbon materials. An optimized extraction method was developed involving ultrasonication in 1:1 methanol:dichloromethane with 5% formic acid. This method achieved recoveries of 60 to 99% per API for an API concentration of 2 μg/g char and 27 to 129% per API for an API concentration of 1 mg/g char. Experiments using a mixture of 82 common APIs revealed that the optimized protocol achieved extraction recoveries above 70% for 29 of these APIs. These results show that the new extraction method could be a useful tool for assessing the regenerative properties of different carbon sorbents.

Hay-based activated biochars obtained using two different heating methods as effective low-cost sorbents: Solid surface characteristics, adsorptive properties and aggregation in the mixed Cu(II)/PAM system

The main aim of the study was to compare the sorption capacity of hay-based activated biochars, obtained using conventional and microwave furnance, relative to copper(II) ions and ionic polyacrylamides (PAM). Surface properties of the solids were characterized by, inter alia, N₂ adsorption/desorption isotherm method, whereas their tendency to aggregation was established turbidimetrically. Adsorption capacity of biochars were performed in the simple and mixed Cu(II)/PAM systems, i.e. the examined suspensions contained one or two adsorbates at the same time. The results indicated that biochar prepared in microwave furnance was characterized by larger micropore area and, as a result, it had higher adsorption capacity relative to Cu(II) ions. At pH 6, when the initial Cu(II) concentration equaled 100 mg/L, the biochar obtained by microwave heating adsorbed 81.5% of Cu(II) ions, whereas the one obtained by conventional heating - 51.6%. Due to high molecular weight, the PAM macromolecules could not penetrate the biochar micropores and thus the polymer adsorbed amounts were similar for both materials. For initial polymer concentration equal to 100 mg/L, the solids adsorbed 65-66.2% of cationic PAM containing 25% of quaternary amine groups. In the mixed system of anionic polyacrylamide and Cu(II) ions, the formation of Cu(II)-PAM complexes occurred, which favored both heavy metal and polymer adsorption on the solid surface. On the other hand, cationic polyacrylamide and heavy metal ions made the contact with the solid difficult for each other. What is more, ionic polyacrylamide and copper(II) ions stimulated the biochar aggregation due to surface charge neutralization and flocculation.

Activated biochar derived from Opuntia ficus-indica for the efficient adsorption of malachite green dye, Cu+2 and Ni+2 from water

Applicability of biochar in water treatment is gaining interest due to its sustainability and low production cost. Herein, the biochar (BC) and activated biochar (ABC) synthesized from the cladodes of Opuntia ficus-indica (OFI) cactus were evaluated as a renewable adsorbent for adsorption of organic as well as inorganic pollutants including malachite green (MG) dye, Cu⁺² and Ni⁺² heavy metals. The modification of biochar with NaOH resulted higher surface basicity regarding more oxygen containing functional groups on the surface. The maximum uptake of 1341 mg g^-1, 49 mg g^-1 and 44 mg g^-1 onto activated biochar for malachite green dye, Cu⁺² and Ni⁺² was acquired through the best fitted Langmuir isotherm model. Pseudo-second-order and Elovich models were found to provide a suitable fit indicating towards the chemisorption of all three components. Film diffusion and chemisorption are the main steps in adsorption of MG dye and heavy metals on activated biochar. The adsorption mechanisms were also hypothesized for adsorption of MG dye, Cu⁺² and Ni⁺². The remarkable adsorption capacities with higher reusability characteristics for adsorption of organic pollutants as well as inorganic heavy metals entrusts this activated biochar as a potential cost-effective adsorbent to mitigate water pollution issue.

Assessing the environmental benefit of a new fertilizer based on activated biochar applied to cereal crops

This study analyzes the environmental benefits that a nitrogen fertilizer based on activated biochar has in comparison to other traditional fertilizers (urea, ammonium nitrate (AN), ammonium sulfate (AS) and di-ammonium phosphate (DAP)). With this aim, activated biochar was generated from residual biomass (barley straw) through physical activation and the resulting biochar was combined with mineral fertilizer to synthethise the fertilizer. This new product was subjected to environmental assessment by means of two different approaches, Life Cycle Assessment (LCA) and nitrogen footprint procedure, both of which considered standard conditions typical of Mediterranean climate and wheat and corn as the fertilized crops. Emission factors of traditional fertilizers were obtained from internally developed models, which were in turn based on real data from literature. As for emission factors of the new product, they were calculated basing on experimental results. Fertilizer impacts in terms of acidification, eutrophication and climate change were estimated, thus revealing a great performance of activated biochar over other fertilizers in terms of reactive nitrogen (Nr), reaching a maximum saving rate of 63% in the amount of Nr released by volatilization and leaching. In addition, this work offers a methodology for environmental analysis of fertilizers and provides useful quantitative indicators for the environmental benefit and the saving of reactive nitrogen, which could contribute to the development of new commercial low N-emissions fertilizers.

Can biochar and designer biochar be used to remediate per- and polyfluorinated alkyl substances (PFAS) and lead and antimony contaminated soils?

Designer biochars can be used to remediate organic and inorganic contaminant polluted soils. Here, a waste timber biochar (BC), a coconut shell activated biochar (aBC) and a wood shrub iron enriched designer biochar (Fe-BC) were investigated. Per- and polyfluorinated alkyl substances (PFAS) contaminated soils with different total organic carbon (TOC) contents (1.6 and 34.2%) were amended with six doses of BC and aBC. Two shooting range soils (TOC 5.2 and 10.2%) contaminated with heavy metals (mainly Pb and Sb) were amended with four doses of BC and Fe-BC. An amendment of 20% BC reduced the PFOS leachate concentration by 86% for the low TOC soil but was not effective for the high TOC soil. An amendment of 1% aBC reduced PFOS leachate concentrations by over >96% for both soils. For the low TOC shooting range soil, a 20% amendment of BC reduced Pb and Sb leaching by 61% and 12%, respectively. An amendment of 20% Fe-BC to soil with low TOC reduced Pb and Sb leaching by 99% and 40%, respectively. The need for "designer" biochars using processes such as iron enrichment or activation should be considered depending on the TOC of the soil, the type of contaminants and remediation goals.

The roles of phosphorus species formed in activated biochar from rice husk in the treatment of landfill leachate

Untreated landfill leachate is a threat to the environment. Here, the phosphoric acid activated biochars prepared from rice husk were successfully used for leachate treatment to achieve a high removal of color (100%), pollutants (>90%), chemical oxygen demand (∼80%) and NH₄⁺-N (100%). The leachate treatment process on phosphoric acid activated biochar could be well described by the pseudo-second order and Langmuir isotherm model, and it was controlled by external mass transfer followed by intra-particle diffusion. The phosphorus species formed in activated biochar could adjust and control the textural properties and structures of biochar, while the phosphorus species of activated biochar could attract humic acid-like organics in the leachate via hydrogen bond and π-π interactions, which were found to significantly enhance the treatment of leachate. The findings provided important insights for efficient treatment of wastewater using agricultural waste residues on an industrial scale.

Engineered biochar from agricultural waste for removal of tetracycline in water

For the first time the present study investigated the production, characterization and application of engineered biochar derived from alfalfa hays for removal of tetracycline (TC) in water. The NaOH activation of alfalfa-derived raw biochar (BC_R) made significant increase in surface area (796.50 m²/g) and pore volume (0.087 cm³/g). The NaOH-activated BC (BC_A) showed much higher adsorption capacity for TC (Q_m = 302.37 mg/g) than BC_R, but comparable to the commercial activated carbon (Calgon F400). The detailed analyses of the kinetic and isotherm studies suggested the strong chemisorptive interactions between TC and BC_A via multiple mechanisms. In addition, intraparticle diffusion was considered as the major limitation for the adsorption of TC onto BC_A. Furthermore, the fixed bed experiments revealed that BC_A could be a promising adsorbent for treating large volume of TC-contaminated water in columns.

The effect of several activated biochars on Cd immobilization and microbial community composition during in-situ remediation of heavy metal contaminated sediment

Chemical activation and microwave assisted activation were adopted to modify biochar. Activated biochars were characterized by SEM, BET, FTIR, XRD and XPS. Raw biochar, activated biochars and commercial activated carbon were compared as remediation strategies for sediment from the Xiangjiang River containing 14.70 mg/kg Cd. After the treatment by activated biochar, the overlying water and pore water concentration of Cd decreased by 71% and 49%, respectively. And the threat of heavy metal along with bioavailability of Cd was depressed. Moreover, the immobilsation of Cd in sediment was related to BET surface area and the content of oxygen containing functional groups of activated biochars. Furthermore, a PCR-DGGE-based experiment was performed for the detection of microbial community. The indigenous microbial community was affected and new microbial community appeared after treat by activated biochar. Activated biochar can be used as an inexpensive and efficient in situ remediation material of sediment containing metal.

Production, characterization, and potential of activated biochar as adsorbent for phenolic compounds from leachates in a lumber industry site

There is growing interest in low-cost, efficient materials for the removal of organic contaminants in municipal and industrial effluents. In this study, the efficiency of biochar and activated biochar, as promising adsorbents for phenol removal, was investigated at high (up to 1500 mg L^-1) and low concentrations (0.54 mg L^-1) in synthetic and real effluents (from wood-residue deposits in Québec), respectively. The performance of both materials was then evaluated in batch adsorption experiments, which were conducted using a low solid/liquid ratio (0.1 g:100 mL) at different phenol concentrations (C₀ = 5-1500 mg L^-1), and at 20 °C. Activated biochars presented higher phenol adsorption capacity compared to biochars due to their improved textural properties, higher micropore volume, and proportion of oxygenated carbonyl groups connected to their surface. The sorption equilibrium was reached within less than 4 h for all of materials, while the Langmuir model best described their sorption process. The maximum sorption capacity of activated biochars for phenol was found to be twofold relative to biochars (303 vs. 159 mg g^-1). Results also showed that activated biochars were more effective than biochars in removing low phenol concentrations in real effluents. In addition, 95% of phenol removal was attained within 96 h (although 85% was removed after 4 h), thus reaching below the maximum authorized concentration allowed by Québec's discharge criteria (0.05 mg L^-1). These results show that activated biochars made from wood residues are promising potential adsorbent materials for the efficient treatment of phenol in synthetic and real effluents.

Biosorptive uptake of Fe(2+), Cu(2+) and As(5+) by activated biochar derived from Colocasia esculenta: Isotherm, kinetics, thermodynamics, and cost estimation

The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia esculenta was investigated for removal of Cu(2+), Fe(2+) and As(5+) from simulated coal mine wastewater. SSAB was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyser. Adsorption isotherm indicated monolayer adsorption which fitted best in Langmuir isotherm model. Thermodynamic study suggested the removal process to be exothermic, feasible and spontaneous in nature. Adsorption of Fe(2+), Cu(2+) and As(5+) on to SSAB was found to be governed by pseudo-second order kinetic model. Efficacy of SSAB in terms of metal desorption, regeneration and reusability for multiple cycles was studied. Regeneration of metal desorbed SSAB with 1 N sodium hydroxide maintained its effectiveness towards multiple metal adsorption cycles. Cost estimation of SSAB production substantiated its cost effectiveness as compared to commercially available activated carbon. Hence, SSAB could be a promising adsorbent for metal ions removal from aqueous solution.

Removal of humic and tannic acids by adsorption-coagulation combined systems with activated biochar

Despite recent interest in transforming biomass into bio-oil and syngas, there is inadequate information on the compatibility of byproducts (e.g., biochar) with agriculture and water purification infrastructures. A pyrolysis at 300°C yields efficient production of biochar, and its physicochemical properties can be improved by chemical activation, resulting in a suitable adsorbent for the removal of natural organic matter (NOM), including hydrophobic and hydrophilic substances, such as humic acids (HA) and tannic acids (TA), respectively. In this study, the adsorption affinities of different HA and TA combinations in NOM solutions were evaluated, and higher adsorption affinity of TA onto activated biochar (AB) produced in the laboratory was observed due to its superior chemisorption tendencies and size-exclusion effects compared with that of HA, whereas hydrophobic interactions between adsorbent and adsorbate were deficient. Assessment of the AB role in an adsorption-coagulation hybrid system as nuclei for coagulation in the presence of aluminum sulfate (alum) showed a synergistic effect in a HA-dominated NOM solution. An AB-alum hybrid system with a high proportion of HA in the NOM solution may be applicable as an end-of-pipe solution.

Evaluation of phosphorus adsorption capacity of sesame straw biochar on aqueous solution: influence of activation methods and pyrolysis temperatures

The phosphorus (P) adsorption characteristic of sesame straw biochar prepared with different activation agents and pyrolysis temperatures was evaluated. Between 0.109 and 0.300 mg L(-1) in the form of inorganic phosphate was released from raw sesame straw biochar in the first 1 h. The release of phosphate was significantly enhanced from 62.6 to 168.2 mg g(-1) as the pyrolysis temperature increased. Therefore, sesame straw biochar cannot be used as an adsorbent for P removal without change in the physicochemical characteristics. To increase the P adsorption of biochar in aqueous solution, various activation agents and pyrolysis temperatures were applied. The amount of P adsorbed from aqueous solution by biochar activated using different activation agents appeared in the order ZnCl2 (9.675 mg g(-1)) > MgO (8.669 mg g(-1)) ⋙ 0.1N-HCl > 0.1N-H2SO4 > K2SO4 ≥ KOH ≥ 0.1N-H3PO4, showing ZnCl2 to be the optimum activation agent. Higher P was adsorbed by the biochar activated using ZnCl2 under different pyrolysis temperatures in the order 600 °C > 500 °C > 400 °C > 300 °C. Finally, the amount of adsorbed P by activated biochar at different ratios of biochar to ZnCl2 appeared in the order 1:3 ≒ 1:1 > 3:1. As a result, the optimum ratio of biochar to ZnCl2 and pyrolysis temperature were found to be 1:1 and 600 °C for P adsorption, respectively. The maximum P adsorption capacity by activated biochar using ZnCl2 (15,460 mg kg(-1)) was higher than that of typical biochar, as determined by the Langmuir adsorption isotherm. Therefore, the ZnCl2 activation of sesame straw biochar was suitable for the preparation of activated biochar for P adsorption.

Activated carbon from biochar: influence of its physicochemical properties on the sorption characteristics of phenanthrene

The relationship between physicochemical properties of biochar-based activated carbons and its adsorption was investigated using an aromatic model compound, phenanthrene. Solid-state (13)C NMR analysis indicated more condensed aromatic structures when pyrolysis temperature increased or after activation process induced. The increasing aromaticity and non-protonated carbon fraction of the activated biochar treated at 300°C amounted to 14.7% and 24.0%, respectively, compared to 7.4% and 4.4% for biochar treated at 700°C. The surface area and pore volume were reduced with the increase in pyrolysis temperature, but increased after activation. Surface characteristics correlated with the initial sorption rate and equilibrium concentration of phenanthrene, but not with the aromaticity. Solid-state (2)H NMR for phenanthrene-d10 saturated activated biochars, however, showed substantial difference in molecular mobility, which might be due to the high aromaticity of the activated biochars. Overall, these results provide an opportunity to manipulate the characteristics of biomass-based adsorbents based on the application needs.