Two-step pyrolysis of malic acid-activated corncob biochar for hydrocarbon pollutant removal from non-aqueous solvent

Co-pyrolysis of municipal and horticultural wastes for enhanced biochar and bio-oil production: A response surface methodology approach

Background The sustainable utilization of Dunaliella salina biomass for biochar and bio-oil production offers a promising approach for pollutant removal and biofuel generation. This study aimed to optimize pyrolysis conditions and evaluate the physicochemical properties of biochar and bio-oil derived from D. salina under real wastewater treatment conditions. Methods D. salina was cultivated in wastewater under controlled aeration (2 L/min) and continuous illumination (100 µmol photons m−2 s−1) for 21 days. Biomass was harvested via centrifugation, dried at 60 °C, and subjected to pyrolysis at temperatures ranging from 400 °C to 900 °C under a nitrogen atmosphere. Biochar yield was determined gravimetrically, and adsorption efficiency was assessed by treating metal-contaminated water with biochar. Bio-oil composition was analysed using GC-MS and NMR spectroscopy, while biochar structural properties were characterized via FE-SEM, XPS, and FTIR. Gas chromatography quantified gas composition, and a life-cycle assessment evaluated environmental impacts. Results Biochar yield decreased from 48.6% at 400 °C to 20.8% at 900 °C, with a corresponding decline in activation energy from 162.3 to 121.9 kJ/mol. DTG analysis showed peak decomposition temperatures shifting from 325 °C to 415 °C, indicating progressive thermal degradation. Bio-oil yield peaked at 45.3% at 550 °C, with dominant compounds including 29.4% aromatics, 22.5% phenols, and 18.3% ketones. Biochar adsorption efficiency reached 95.0% for Pb2+, 96.0% for Cd2+, and 90.0% for As³+, with a maximum surface area of 600 m2/g at 650 °C. Life-cycle analysis indicated a 60.9% reduction in GWP and a 73.3% decrease in fossil resource depletion for biochar compared to bio-oil production. Conclusion Biochar and bio-oil from D. salina demonstrated high adsorption efficiency and fuel potential, supporting their application in environmental remediation and sustainable energy production.

Six slow pyrolysis biochars viz. farmyard manure (FM), water hyacinth (WH), domestic organic waste (DW), quick compost (QC), corn cob (CC) and rice straw (RS) were analyzed for their physical and chemical properties. Biochar yielding capacity varied from 34 to 51%, depending on the used feedstock. Water hyacinth biochar exhibited the highest water holding capacity (495%), whereas corn cob biochar had the lowest (146%) regardless of its highest pore volume. Brunauer-Emmett-Teller (BET) specific surface area was found maximum among the plant derived biochars except corn cob. Rice straw biochar exhibited the least mean pore diameter while highest in domestic organic waste. All biochars possessed pH values more than 9. CEC of water hyacinth (WH) was highest, while lowest was in quick compost (QC) biochar. Smallest average particle size (0.54 ?m2) was exhibited by water hyacinth biochar. Organic carbon content ranged from 33 to 49%. Nutrient (N, P, K and S) status of biochar produced from domestic organic waste (DW) was found the maximum compared to the rest and corn cob (CC) biochar showed the lowest nutritional value.Bangladesh J. Sci. Res. 29(2): 111-122, December-2016

Pyrolysis of waste materials to produce biochar is an excellent and suitable alternative supporting a circular bio-based economy. One of the properties attributed to biochar is the capacity for sorbing organic contaminants, which is determined by its composition and physicochemical characteristics. In this study, the capacity of waste-derived biochar to retain volatile fuel organic compounds (benzene, toluene, ethylbenzene and xylene (BTEX) and fuel oxygenates (FO)) from artificially contaminated water was assessed using batch-based sorption experiments. Additionally, the sorption isotherms were established. The results showed significant differences between BTEX and FO sorption on biochar, being the most hydrophobic and non-polar contaminants those showing the highest retention. Furthermore, the sorption process reflected a multilayer behaviour and a relatively high sorption capacity of the biochar materials. Langmuir and Freundlich models were adequate to describe the experimental results and to detect general differences in the sorption behaviour of volatile fuel organic compounds. It was also observed that the feedstock material and biochar pyrolysis conditions had a significant influence in the sorption process. The highest sorption capacity was found in biochars produced at high temperature (> 400°C) and thus rich in aromatic C, such as eucalyptus and corn cob biochars. Overall, waste-derived biochar offers a viable alternative to be used in the remediation of volatile fuel organic compounds from water due to its high sorption capacity.

Petroleum-contaminated soil bioremediation and microbial community succession induced by application of co-pyrolysis biochar amendment: An investigation of performances and mechanisms

In view of the rainwater pollution problems in highway runoff on the Northwest Expressway, especially heavy metal pollution and poor soil water retention, this study focused on the sandy soils along the highway sides in Qilian Mountain National Park, Gansu Province. It investigated the removal of pollutants as well as water and fertilizer retention effects in simulated highway rainwater runoff using four amendments: carboxymethyl cellulose (CMC), corn straw biochar, corn cob biochar, and rice husk biochar, both individually and in combination. Through permeability tests, evaporation tests, and static adsorption experiments, the optimal soil treatment for runoff rainwater was determined. Experiments showed that mixing soil with quartz sand in a 4:6 ratio and adding 5% rice husk biochar and 0.1% CMC can significantly enhance the adsorption of various pollutants and improve soil moisture retention. We packed the initially selected improved soil matrix into columns, initiated operation, and set the influent flow rate to 9 mL/min. During stable operation, the average retention rates of nutrients-ammonia nitrogen (NH4+-N), total phosphorus, and chemical oxygen demand-from highway runoff were 81.75%, 66.72%, and 77.97%, while the average removal rates of copper (II) (Cu2+) and chromium (VI) (Cr6+) were 91.94% and 84.18%, respectively. After operation, the residual forms of copper (Cu) and chromium (Cr) in the soil matrix accounted for 56.96% and 52.28%. The transformation of Cu and Cr into stable residual forms with low migration risk effectively reduced their environmental impact.

Treatment of anaerobic digested effluent in biochar-packed vertical flow constructed wetland columns: Role of media and tidal operation

An electron transfer tuning strategy for the efficient degradation of tetracycline hydrochloride by Fe-N co-doped carbon materials activated with peroxymonosulfate

Two-step pyrolysis biochar derived from agro-waste for antibiotics removal: Mechanisms and stability

It is widely believed that biochar plays an essential role in sequestrating pollutants. The impacts of biochar on microbial growth, and consequently on the environmental fate of pollutants, however, remains poorly understood. In this study, wheat-straw-derived biochar was used to investigate how biochar amendment affected Shewanella oneidensis MR-1 growth and roxarsone transformation in water under anaerobic conditions. Three biochar with different physicochemical properties were used to mediate the roxarsone degradation. The results showed that the degradation rate of roxarsone could be accelerated by the increase of biochar pyrolysis temperature. From the characterization of biochar, the total specific surface area, micropore surface area and micropore volume of biochar increase, but the average pore diameter decreases as the pyrolysis temperature increases. Through infrared spectroscopy analysis, it was found that as the pyrolysis temperature increases, the degree of condensation of biochar increases, thereby increasing the pollutant removal rate. From the changes of the relative concentration of MR-1 and its secreted extracellular polymer content, the growth promotion ability of biochar also increases as the pyrolysis temperature increases. These results suggest that wheat-straw-derived biochar may be an important agent for activating microbial growth and can be used to accelerate the transformation of roxarsone, which could be a novel strategy for roxarsone remediation.

This study synthesized a highly efficient KOH-treated sunflower stem activated carbon (KOH-SSAC) using a two-step pyrolysis process and chemical activation using KOH. The resulting material exhibited exceptional properties, such as a high specific surface area (452 m2/g) and excellent adsorption capacities for phenol (333.03 mg/g) and bisphenol A (BPA) (365.81 mg/g). The adsorption process was spontaneous and exothermic, benefiting from the synergistic effects of hydrogen bonding, electrostatic attraction, and stacking interactions. Comparative analysis also showed that KOH-SSAC performed approximately twice as well as sunflower stem biochar (SSB), indicating its potential for water treatment and pollutant removal applications. The study suggests the exploration of optimization strategies to further enhance the efficiency of KOH-SSAC in large-scale scenarios. These findings contribute to the development of improved materials for efficient water treatment and pollution control.