Synthesis and efficiency comparison of reed straw-based biochar as a mesoporous adsorbent for ionic dyes removal

Manganese-modified reed biochar decreased nutrients and methane release from algae debris-contaminated sediments

Biochar is one of the ways for carbon storage, pollution control and biosolid reuse. Aquatic plant reeds are widely used in nutrient removal in wetlands and have huge biomass. Nonetheless, little is known regarding the effects of reed-based biochar on sediments. In this study, reed-based biochar (BC) modified with or without Mn-oxidizers (MBC) was prepared to investigate their impacts on nutrient removal, methane (CH4) emission fluxes, and CH4 concentration and microbial community in sediments for 20 days. We found that BC and MBC significantly reduced CH4 emission fluxes by 56.84 ± 10.47% and 69.95 ± 0.76% (p < 0.05) compared to control (CK), respectively. In addition, BC and MBC had a higher efficiency of nutrient removal, and the removal rate increased by 4.4% for NH4+-N and 10.13% for TN in BC and by 3.21%, 8.43% and 18.29% for NH4+-N, TN and TP in MBC, respectively. Proteobacteria, Chloroflexi, Bacteroidota, Firmicutes, Desulfobacterota and Acidobacteriota were the predominant phyla in sediments and might contribute to nutrient removal. Network analysis revealed that biochar addition promoted interspecific competition in sediments, which could be more beneficial for enhancing the stability of microbial community structures. The decreased mcrA (CH4 bioproduction) abundance but increased pomA (CH4 oxidation) abundance was detected in BC and MBC compared to CK, explaining biochar-reduced CH4 emissions. This study highlights that reed straw-based biochar can be used in the in-situ remediation of polluted sediments and provides a choice for carbon storage and pollution control for managers.

Unveiling the reactor effect: a comprehensive characterization of biochar derived from rubber seed shell via pyrolysis and in-house reactor

Utilization of agricultural waste to produce biochar has already proven to be an efficient method for transforming waste into valuable resources. In this study, rubber seed shell (RSS) was utilized to prepare two biochar samples via an in-house built reactor (RSSBC-1) and a pyrolysis reactor (RSSBC-2) under identical conditions (600 °C for 3 h at a heating rate of 10 °C per min). A comprehensive characterization of the prepared biochar samples was carried out to reveal the reactor effect on the biochar properties. For this, proximate and ultimate analyses were carried out which estimated the carbon stability, polarity, and aromaticity of the biochar samples. For RSSBC-1, C and N content were higher, whereas H and O content were higher for RSSBC-2, as found from elemental, EDX, and XPS analyses. Point of zero charge (PZC) values of 7.65 and 6.14 for RSSBC-1 and RSSBC-2, respectively, emphasized the importance of pH in the removal of ionic contaminants. Furthermore, the superiority of RSSBC-1 in terms of specific surface area of 336.02 m2 g-1 compared to 299.09 m2 g-1 of RSSBC-2 was articulated by BET analysis. XPS and FESEM analyses revealed the chemical state of surface elements and surface morphology, respectively of the biochar samples. XRD patterns assured the amorphous nature of biochar samples, and functional groups were well depicted by FTIR analysis. DLS showed a larger average hydrodynamic diameter for RSSBC-2 (248.68 nm) with a zeta potential of -14.91 mV compared to RSSBC-1 (115.23 nm) with a heterogeneous charge distribution (-16.72 mV and +37.61 mV). TGA analysis revealed the thermal stability of both biochar samples. Overall, the results explicitly depict a distinction in the properties of biochar samples prepared in two different reactors, where RSSBC-1, with its superior properties suggests the in-house built reactor as a promising alternative to expensive pyrolytic reactors for waste valorization.

A comprehensive review of enhanced CO2 capture using activated carbon derived from biomass feedstock

The increasing level of atmospheric CO2 requires the urgent development of effective capture technologies. This comprehensive review thoroughly examines various methods for the synthesis of carbon materials, modification techniques for converting biomass feedstock into carbon materials and pivotal factors impacting their properties. The novel aspect of this review is its in-depth comparison of how these modifications specifically affect the pore structure and surface area together with the exploration of the mechanism underlying the enhancement of CO2 adsorption performance. Additionally, this review addresses research gaps and provides recommendations for future studies concerning the advantages and drawbacks of CO2 adsorbents and their prospects for commercialization and economic feasibility. This article revealed that among the various strategies, template carbonization offers a viable option for providing control of the material pore diameter and structure without additional modification treatments. Optimizing the pore structure of activated carbons, particularly those activated with agents such as KOH and ZnCl2, together with synthesizing hybrid activated carbons using multiple activating agents, is crucial for enhancing their CO2 capture performance. Cost-benefit analysis suggests that biomass-derived activated carbons can significantly meet the escalating demand for CO2 capture materials, offering economic advantages and supporting sustainable waste management.

Facile synthesis of TiO2@ZnO nanoparticles for enhanced removal of methyl orange and indigo carmine dyes: Adsorption, kinetics

Water pollution represents one of the most important problems affecting the health of living organisms, so it was necessary to work on the formation of active materials to get rid of pollutants. In this study, Titanium dioxide (TiO2) doping Zinc oxide (ZnO) nanocomposites were produced via simple sonication method at 500 Hz in ethanol medium. At different weight concentrations (2.5, 5, 7.5, and 10 %). The morphology, structure configuration, chemical bonding, crystalline phase, and surface properties of obtained nanocomposites were characterized via FESEM, BET, XRD, XPS, RAMAN and FTIR instrumentation. The nanocomposites were employed as an adsorbent to eliminate the methyl orange (MO) and Indigo Carmine (IC) dyes from an aqueous solution. Batch removal experiments revealed that the elimination of MO and IC dyes by the TiZnO surface was pH and doping Ti concentration-dependent, with maximum removal occurring at pH = 7 for MO and pH = 3 for IC contaminants at 10 % doping Ti concentration (Ti (10 %)@ZnO). Langmuir model fit the absorptive removal of MO and IC dyes into the Ti (10 %)@ZnO surface well. The maximal removal capacity of Ti (10 %)@ZnO nanocomposite was found to be 994.24 mg. g-1 for MO and 305.39 mg. g-1 for IC. The Ti (10 %)@ZnO nanocomposite showed remarkable high stability towards the removal of both dyes through consecutive four cycles.

Sequestration of cyanide ions from aqueous medium by physio-chemically fabricated biochar of peels of banana and grape fruit in ecofriendly way

Pakistan is an agricultural country producing plenty of fruits, like: mango, banana, apple, peaches, grapes, plums, variety of citrus fruits including lemon, grapefruit, and oranges. So far the peels of most of the fruits are usually wasted and not properly utilized anywhere. In this work, the peels of banana and grapefruit are converted into biochar by slow pyrolysis under controlled supply of air and used for sequestering cyanide ions from aqueous medium after chemical modification with ZnCl2 and sodium dodecyl sulfate (SDS). The modified biochar was characterized by various instrumental techniques, like: SEM, FTIR, TGA, and CHNS. Different parameters, like: time, temperature, pH, and dose of adsorbent affecting the adsorption of cyanide ions, onto prepared biochar were optimized and to understand the adsorption phenomenon, kinetic and thermodynamic studies were performed. Concentration of cyanide ions was estimated by employing standard ion selective electrode system and it is found that Sodium Dodecyl Sulfate treated biochar of banana peels shown more adsorption capacity, i.e.,: 17.080 mg/g as compared to all samples. Present work revealed that the biochar produced from the fruit waste has sufficient potential to eliminate trace quantities of cyanide from water, especially after treatment with sodium dodecyl sulfate.

Advancements in application of modified biochar as a green and low-cost adsorbent for wastewater remediation from organic dyes

Synthetic organic dyes, which are resistant to biodegradation, pose a notable health risk, potentially leading to cancer and respiratory infections. Researchers have addressed this concern by exploring physicochemical methods to remove organic dyes from wastewater. A particularly promising solution involves modified biochar adsorbents, which demonstrate high efficiency in organic dye removal. Biochar, a charcoal-like material derived from biomass pyrolysis, offers advantages such as low cost, eco-friendliness, high efficiency and reusability. Beyond its role in sustainable soil remediation, biochar proves effective in removing organic dyes from wastewater after undergoing physical or chemical modification. Acid-base activation or metal-heteroatom impregnation enhances biochar's adsorption capacity. This comprehensive review examines the attributes of biochar, common methods for production and modification, and the impacts of raw materials, pyrolysis temperature, heating rate and residence time. It further elucidates the biochar adsorption mechanism in the removal of organic dyes, assessing factors influencing efficiency, including biochar feedstock, solution pH, adsorption temperature, particle size, initial dye concentration, biochar dosage and reaction time. It explores challenges, opportunities, reusability and regeneration methods of biochar in treating organic dye wastewater. It also discusses recent advances in organic dye removal using adsorption-based biochar. The review ultimately advocates for enhancing biochar's adsorption performance through post-modification.

Efficient Adsorption of Nitrogen and Phosphorus in Wastewater by Biochar

Nitrogen and phosphorus play essential roles in ecosystems and organisms. However, with the development of industry and agriculture in recent years, excessive N and P have flowed into water bodies, leading to eutrophication, algal proliferation, and red tides, which are harmful to aquatic organisms. Biochar has a high specific surface area, abundant functional groups, and porous structure, which can effectively adsorb nitrogen and phosphorus in water, thus reducing environmental pollution, achieving the reusability of elements. This article provides an overview of the preparation of biochar, modification methods of biochar, advancements in the adsorption of nitrogen and phosphorus by biochar, factors influencing the adsorption of nitrogen and phosphorus in water by biochar, as well as reusability and adsorption mechanisms. Furthermore, the difficulties encountered and future research directions regarding the adsorption of nitrogen and phosphorus by biochar were proposed, providing references for the future application of biochar in nitrogen and phosphorus adsorption.