Fourteen metal/metalloid elements and sixteen polycyclic aromatic hydrocarbons (PAHs) within biochars were quantified to investigate how heat treatment temperatures (HTTs) and feedstocks affect their concentration and composition. Concentrations and composition of metals/metalloids were strongly dependent upon feedstocks rather than HTTs. HTTs significantly affected concentrations and composition of PAHs. The highest concentration of PAHs was observed for plant residue-derived biochars (PLABs) produced at 450 °C and the opposite result was for animal waste-derived bichars. High mineral content was responsible for depolymerization of organic matter (OM), which facilitated high production of PAHs. High HTTs pyrolysis or combustion PAHs (COMB) of PLABs possibly blocks their micropores derived from other components within OM and leads to a decline of CO2-surface areas (CO2-SAs). Concentration of ∑COMB or individual PAH was affected by biochar properties, including composition and contents of functional groups, ash content, and CO2-SAs. PLABs produced at 600 °C were recommended for low toxicity.

The presence of polycyclic aromatic hydrocarbons (PAHs) has been postulated as a mechanism by which biochar might mitigate N2O emissions. We studied whether and to what extent N2O emissions were influenced by the three most abundant PAHs in biochar: naphthalene, phenanthrene and pyrene. We hypothesised that biochars contaminated with PAHs would show a larger N2O mitigation capacity and that increasing PAH concentrations in biochar would lead to higher mitigation potentials. Our results demonstrate that the high-temperature biochar (550 °C) had a higher capacity to mitigate soil N2O emissions than the low-temperature biochar (350 °C). At low PAH concentrations, PAHs do not significantly contribute to the reductions in soil N2O emissions; while biochar stimulated soil N2O emissions when it was spiked with high concentrations of PAHs. This study suggests that the impact of biochar on soil N2O emissions is due to other compositional and/or structural properties of biochar rather than to PAH concentration.

Polycyclic aromatic hydrocarbons (PAH), as a part of dissolved organic matter (DOM), are environmental pollutants of the marine compartment. This study investigates the origin of PAH, which is supposed to derive mainly from anthropogenic activities, and their alteration along the salinity gradient of the Baltic Sea. Pyrolysis in combination with gas chromatography and two mass selective detectors in one measurement cycle are utilized as a tool for an efficient trace analysis of such complex samples, by which it is possible to detect degradation products of high molecular structures. Along the north–south transect of the Baltic Sea a slightly rising trend for PAH is visible. Their concentration profiles correspond to the ship traffic as a known anthropogenic source, underlined by the value of special isomer ratios such as phenanthrene and anthracene (0.31–0.45) or pyrene and fluoranthene (0.44–0.53). The detection of naphthalene and the distribution of its alkylated representatives support this statement.

Biochar has attracted recent research interest as a metal adsorbent. The heavy metal adsorption capacity of biochar can be controlled by the carbonization of biochar. The adsorption characteristics of heavy metals (Pb, Cu, and Cd) by peat moss-derived biochars produced under different carbonization conditions were investigated by a series of batch experiments. Biochars were produced by the pyrolysis of peat moss over a temperature range of 400–1000 °C for 30–90 min. Biochar produced at 800 °C for 90 min was the most efficient for the removal of Pb and Cu, when weight loss ratio was considered. The pseudo-second-order and Langmuir models adequately described kinetics and isotherms, respectively, of heavy metal adsorption on peat moss-derived biochar, indicating that heavy metal ions were chemically adsorbed on the adsorption sites as uniform monolayer. The peat moss-derived biochar showed the highest maximum adsorption capacity for Pb (81.3 mg/g), followed by Cd and Cu, which were 39.8 and 18.2 mg/g, respectively. This study shows that peat moss-derived biochar is an effective adsorbent to remediate heavy metal-contaminated water.

The carbon rich material obtained from pyrolysis process, i.e. biochar, has been widely discussed during the last decade due to its utilisation as a soil amendment. Furthermore, there is an unsolved question of biomass disposal from phytoremediation technologies. The idea of contaminated biomass pyrolysis has appeared, but there is lack of information about possible biochar utilisation obtained by this process. The aim of our study was to observe sorption properties of biochar prepared from contaminated biomass and release of contaminants from biochar back into the environment. The biomass of fast growing trees and maize was harvested on a site significantly damaged by risk element contamination (Cd, Pb and Zn). Plant biomass was pyrolysed and then the batch (de)sorption experiments were settled. The results confirmed no significant differences in metal sorption ability between biochars prepared from contaminated and uncontaminated biomass under the same conditions. The trend of maximum sorption capacity of observed matrices followed the order: wood biochar + soil (WB + soil) > wood uncontaminated biochar + soil (WUB + soil) > maize biochar + soil (MB + soil) > soil for cadmium, WB + soil > WUB + soil > soil for lead and MB + soil > WUB + soil > WB + soil > soil for zinc. Despite of increase of Zn desorption from wood biochars, maximum sorption capacity of the final WB + soil system was comparable to the WUB+soil sample. Our laboratory experiments showed high potential of biochar from contaminated plants as a soil amendment with sorption abilities and minimal risk of metal release.

Biochar is an organic carbon (OC) and plant nutrient-rich substance that may be an ideal amendment for bolstering soil organic matter and nutrient contents. Two biochars were produced by pyrolysis at 350 °C from pine chips (Pinus taeda) and swine manure solids (Sus scrofa domesticus). The biochar total elemental composition was quantified using inductively coupled plasma spectrometer and their surface chemical composition examined using a combination of scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). The biochars were mixed into triplicate pots containing Lauderhill muck (Euic, hyperthermic Lithic Haplosaprist) at 0, 2.5, 5, and 10 % (dry mass). Four simulated water infiltration events were conducted during the 124-day incubation to assess the potential alteration in the leaching potential of soluble soil nutrients. At termination, the muck’s fertility characteristics were assessed, and dissolved cations were measured in water leachates. Neither biochars significantly increased the muck’s OC contents. Swine manure biochar contained higher K, Mg, Na, and P concentrations, and these differences were observable in SEM and EDS as differing amounts of surface-precipitated Mg and K salts. Correspondingly, swine manure biochar at all three applications rates significantly increased Mehlich 1-s K, P, Mg, and Na concentrations. Pine chip biochar only improved the Mehlich 1-extractable K concentration but did reduce soluble P concentrations. Water leachates from swine manure biochar treated wetland soil contained significantly higher soluble P concentrations that could create water quality issue in downstream ecosystems.

New porous carbonaceous adsorbents were prepared from an oily sludge generated in a fuel oil storage tank using pyrolysis with and without activation by KOH at 600 °C. The pore characteristics of the activated carbonaceous adsorbent (AC), due to the formation of micropores and mesopores structure, were considerably better than those of non-activated carbonaceous adsorbent (NA). The adsorption of Cd from aqueous solutions on the produced carbonaceous adsorbents was optimized using the Taguchi method. Under optimum conditions, the Cd adsorption efficiency for the NA and AC was obtained to be 77.7 and 98.2 %, respectively. The initial concentration and the adsorbent dose were the most significant factors affecting the removal of Cd by NA and AC, respectively. The adsorption data for the AC were well fitted by the Langmuir, Freundlich, and Redlich-Peterson isotherms models. The regeneration and reuse of the adsorbents in the three cycles of Cd adsorption-desorption were possible. The carbonaceous adsorbents had acceptable efficiency for the removal of Cd from a mine wastewater. Based on the obtained results, the oily sludges available in huge amounts in the petroleum industry proved to be a potential precursor resource for the production of the porous carbonaceous adsorbents, particularly for application in the wastewater treatment.

Photodegradation of methylene blue (MB) was studied on TiO₂in the presence of activated carbon (AC) prepared from the sawdust of a soft wood by physical activation under CO₂flow, by pyrolysis under N₂flow, and by chemical activation with ZnCl₂and H₃PO₄under N₂flow. MB photodegradation was performed under UV and UV-visible irradiation to verify the scaling-up of the present TiO₂-AC binary materials. It was verified that oxygenated surface groups on carbon were intrinsically photoactive, and a synergy effect between both solids has been estimated from the first-order apparent rate constants in the photodegradation of MB. This effect enhances the photoactivity of TiO₂up to a factor of about 9 under visible irradiation, and it was associated to the surface properties of AC.

New, sustainable, and low-cost materials that can simultaneously remove a range of wastewater contaminants, such as heavy metals and pharmaceutical residues, are needed. In this work, modified biochars were produced by dip-coating hickory or bagasse biomass in carbon nanotube (CNT) suspensions with or without sodium dodecylbenzenesulfonate (SDBS)-aided dispersion prior to slow pyrolysis in a N₂ environment at 600 °C. The sulfapyridine (SPY) and lead (Pb) sorption ability of pristine hickory (HC) and bagasse (BC) biochars and the modified biochars with (HC-SDBS-CNT and BC-SDBS-CNT, respectively) and without (HC-CNT and BC-CNT) SDBS was assessed in laboratory aqueous batch single- and binary-solute system. The greatest removal of SPY and Pb was observed for HC-SDBS-CNT (86 % SPY and 71 % Pb) and BC-SDBS-CNT (56 % SPY and 53 % Pb), whereas HC-CNT, BC-CNT, and the pristine biochars removed far less. This can be attributed to the fact that surfactant could prevent the aggregation of CNTs and thus promote the distribution and stabilization of individual CNT nanoparticle on the biochar surface to adsorb the contaminants. The observation of no significant change in Pb sorption capacities of the surfactant-dispersed CNT-modified biochars in the presence of SPY, or vice versa, was indicative of site-specific sorption interactions and a lack of significant competition for functional groups by the two sorbates. These results suggest that products of hybrid technologies, such as biochars modified with CNTs, can yield multi-sorbents and may hold excellent promise as a sustainable wastewater treatment alternative.

The potential phytotoxicity of water extractable toxicants in a typical corn stover biochar, the product of fast pyrolysis, was investigated using an aqueous biochar extract on a soil-less bioassay with tomato plants. The biochar dosage of 0.0–16.0 g beaker⁻¹ resulted in an inverted U-shaped dose-response relationship between biochar doasage and seed germination/seedling growth. This indicated that tomato growth was slightly stimulated by low dosages of biochar and inhibited with higher dosages of biochar. Additionally, antioxidant enzyme activities in the roots and leaves were enhanced at lower dosages, but rapidly decreased with higher dosages of biochar. With the increased dosages of biochar, the malondialdehyde content in the roots and leaves increased, in addition with the observed morphology of necrotic root cells, suggesting that serious damage to tomato seedlings occurred. EC50 of root length inhibition occurred with biochar dosages of 9.2 g beaker⁻¹ (3.5th day) and 16.7 g beaker⁻¹ (11th day) (equivalent to 82.8 and 150.3 t ha⁻¹, respectively), which implied that toxicity to the early growth of tomato can potentially be alleviated as the plant grows.