One-step synthesis of ZnFe2O4-loaded biochar derived from leftover rice for high-performance H2S removal

Adsorptive removal of gaseous contaminants using biomass-based adsorbents

Biomass-based adsorbents have emerged as attractive materials for the adsorptive removal of gaseous pollutants due to their abundance in nature, low cost, and environmental friendliness. The modification of the adsorbent surfaces has been regarded as an intriguing technique for improving and enhancing their adsorption capacity for efficient removal of pollutants. The present study investigates the most recent developments and applications of biomass-derived adsorbents for removing various gaseous contaminants from air and gas streams. The use of biomass materials such as agricultural waste and wood residue to synthesize adsorbents provides a long-term solution to environmental pollution. This is due to the fact that biomass-derived adsorbents can be designed to have a large surface area, porosity, and surface functionality, thereby increasing their adsorption capacity and selectivity for target pollutants using a variety of chemical processes such as carbonization, activation, and modification. This study presents a comprehensive report on the use of biomass-based adsorbents for the removal of various gaseous pollutants such as carbon dioxide (CO2), volatile organic compounds (VOCs), nitrogen oxides (NO x ), sulfur dioxide (SO2), hydrogen sulphide (H2S) and multi-gas components. The surface chemistry of biomass adsorbents, in addition to their porous nature, is discussed. Multi-gas adsorption properties and the regeneration of biomass adsorbent are also discussed. The challenges and future prospects for developing biomass-based adsorbents for gaseous pollutant removal are also discussed, emphasizing the importance of a thorough understanding of adsorption mechanisms, scalability of manufacturing processes, and integration with existing air purification technologies. The findings of this study present biomass-derived adsorbents as a promising alternative for mitigating the challenges associated with the danger of gaseous pollutants, contributing to sustainable environmental management and public health protection.

Progress on hydrogen sulfide removal: From catalytic oxidation to plasma-assisted treatment

Air pollution is a long-standing environmental challenge as well an important economic subject. Hydrogen sulfide is one the major pollutants in the industrial releases. This review focuses on the thermochemical treatment of hydrogen sulfide based on the most recent works to date regarding its removal. By analyzing fundamental steps in chemical reaction engineering, some useful factors are emphasized since they are often neglected in scientific studies, catalysts design and process scale-up. From processing side, the fluid flow conditions including velocity, H2S concentration, relative humidity, temperature and pressure strongly influence the kinetic behavior and so the catalytic performance of the H2S removal reactor. From material side, the catalyst properties including nature, porosity, pore types, size, sites distribution and layer structuration largely influence the removal performance via among others the accessibility to catalytic sites, pores connection and mass transfer resistance. Plasma-assisted catalytic removal of H2S combines many novelties in comparison with a classical thermo-catalytic process. From patents review, we can see that main concerns are about electrodes mounting, reactor lifetime and modular design to solve the problems in the industrial practice. We attempt to provide for scientists, engineers and industrialists a guidance on the design of catalysts and processes for H2S removal which could be applied in laboratorial studies and industrial processes as well.

An innovative outlook on utilization of agro waste in fabrication of functional nanoparticles for industrial and biological applications: A review

The burning of an agro waste residue causes air pollution, global warming and lethal effects. To overcome these obstacles, the transformation of agro waste into nanoparticles (NPs) reduces industrial expenses and amplifies environmental sustainability. The concept of green nanotechnology is considered as a versatile tool for the development of valuable products. Although a plethora of literature on the NPs is available, but, still scientists are exploring to design more novel particles possessing unique shape and properties. So, this review basically summarises about the synthesis, characterizations, advantages and outcomes of the various agro waste derived NPs.

Abatement of odor emissions from wastewater treatment plants using biochar

Odor is a critical environmental problem that negatively affects people's quality of life. Wastewater treatment plants (WWTPs) often emit various odorous compounds, such as ammonia, sulfur dioxide, and organosulfur. Abatement of odor emissions from WWTPs using biochar may contribute to achieving carbon neutrality due to the carbon negative nature, CO2 sorption, and negative priming effects of biochar. Biochar has a high specific surface area and microporous structure with appropriate activation, which is suitable for sorption purposes. Various research directions have been proposed to determine the biochar removal efficiency for different odorants released from WWTPs. According to the literature survey, the pre- and post-treatments (e.g., thermal treatment, chemical treatment, and metal impregnation) of biochar could enhance the removal capacity for the odorants emitted from WWTPs at comparable conditions, compared to unmodified biochar. The feedstock and production condition (particularly, pyrolysis temperature) of a biochar and initial concentration of an odorant markedly affect the biochar's odorant removal capacity and efficiency. Moreover, different adsorption systems for the removal of odorants emitted from WWTPs follow different adsorption models. Further research is required to establish the practical use of biochar for the mitigation of odors released from WWTPs.

Power-to-X electroscrubbing parameter analysis for biogas desulfurization

A new power-to-X desulfurization technology has been examined. The technology uses only electricity to oxidize the hydrogen sulfide (H₂S) found in biogas to elemental sulfur. The process works by using a scrubber where the biogas comes into contact with a chlorine containing liquid. This process is capable of removing close to 100% of H₂S in biogas. In this paper a parameter analysis of process parameters has been carried out. In addition a long term test of the process has been performed. It has been found that the liquid flow rate has a small but notable influence on the process' performance on removing H₂S. The efficiency of the process largely depends on total amount of H₂S flowing through the scrubber. As the H₂S concentration increases, the amount of chlorine required for the removal process is also increased. A high amount of chlorine in the solvent may lead to unwanted side reactions.

Biomass Derived N-Doped Porous Carbon Made from Reed Straw for an Enhanced Supercapacitor

Developing advanced carbon materials by utilizing biomass waste has attracted much attention. However, porous carbon electrodes based on the electronic-double-layer-capacitor (EDLC) charge storage mechanism generally presents unsatisfactory capacitance and energy density. Herein, an N-doped carbon material (RSM-0.33-550) was prepared by directly pyrolyzing reed straw and melamine. The micro- and meso-porous structure and the rich active nitrogen functional group offered more ion transfer and faradaic capacitance. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) measurements were used to characterize the biomass-derived carbon materials. The prepared RSM-0.33-550 possessed an N content of 6.02% and a specific surface area of 547.1 m² g^-1. Compared with the RSM-0-550 without melamine addition, the RSM-0.33-550 possessed a higher content of active nitrogen (pyridinic-N) in the carbon network, thus presenting an increased number of active sites for charge storage. As the anode for supercapacitors (SCs) in 6 M KOH, RSM-0.33-550 exhibited a capacitance of 202.8 F g^-1 at a current density of 1 A g^-1. At a higher current density of 20 A g^-1, it still retained a capacitance of 158 F g^-1. Notably, it delivered excellent stability with capacity retention of 96.3% at 20 A g^-1 after 5000 cycles. This work not only offers a new electrode material for SCs, but also gives a new insight into rationally utilizing biomass waste for energy storage.

Advancement of biochar-aided with iron chloride for contaminants removal from wastewater and biogas production: A review

The use of fossil fuels, emission of greenhouse gases (GHG) into the atmosphere, and waste pose a problem to the environment and public health that urgently needs to be dealt with. Among numerous chemical activating agents that can be added to anaerobic digestion (AD) to enhance nutrient removal and increase the quality and quantity of biomethane, iron chloride (FeCl₃) is the one that has the lowest cost and is the most environmentally friendly. This state-of-the-art review aims to revise the influence of FeCl₃ on the Brunauer-Emmett-Teller (BET) surface area of biochar and its ability to increase methane (CH₄) yield and remove contaminants from biogas and wastewater. The novelty of the study is that FeCl₃, an activating agent, can increase the BET surface area of biochar, and its efficacy increases when combined with zinc chloride or phosphoric acid. Regarding the removal of contaminants from wastewater and biogas, FeCl₃ has proven to be an effective coagulant, reducing the chemical oxygen demand (COD) of wastewater and hydrogen sulfide in biogas. The performance of FeCl₃ depends on the dosage, pH, and feedstock used. Therefore, FeCl₃ can increase the BET surface area of biochar and CH₄ yield and remove contaminants from wastewater and biogas. More research is needed to investigate the ability of FeCl₃ to remove water vapor and carbon dioxide during biogas production while accounting for a set of other parameters, including FeCl₃ size.

Adsorptive Features of Magnetic Activated Carbons Prepared by a One-Step Process towards Brilliant Blue Dye

Water pollution by dyes has been a major environmental problem to be tackled, and magnetic adsorbents appear as promising alternatives to solve it. Herein, magnetic activated carbons were prepared by the single-step method from Sapelli wood sawdust, properly characterized, and applied as adsorbents for brilliant blue dye removal. In particular, two magnetic activated carbons, MAC1105 and MAC111, were prepared using the proportion of biomass KOH of 1:1 and varying the proportion of NiCl₂ of 0.5 and 1. The characterization results demonstrated that the different proportions of NiCl₂ mainly influenced the textural characteristics of the adsorbents. An increase in the surface area from 260.0 to 331.5 m² g^-1 and in the total pore volume from 0.075 to 0.095 cm³ g^-1 was observed with the weight ratio of NiCl₂. Both adsorbents exhibit ferromagnetic properties and the presence of nanostructured Ni particles. The different properties of the materials influenced the adsorption kinetics and equilibrium of brilliant blue dye. MAC111 showed faster kinetics, reaching the equilibrium in around 10 min, while for MAC1105, it took 60 min for the equilibrium to be reached. In addition, based on the Sips isotherm, the maximum adsorption capacity was 98.12 mg g^-1 for MAC111, while for MAC1105, it was 60.73 mg g^-1. Furthermore, MAC111 presented the potential to be reused in more adsorption cycles than MAC1105, and the use of the adsorbents in the treatment of a simulated effluent exhibited high effectiveness, with removal efficiencies of up to 90%.

Preparation of magnesium Ferrite-Doped magnetic biochar using potassium ferrate and seawater mineral at low temperature for removal of cationic pollutants

Magnetic biochar has captured a great interest for remediation of environment as an easily separable carbonous adsorbent. Herein, a highly adsorptive magnetic biochar was manufactured through seawater mineral and K₂FeO₄ co-promoted pyrolysis of jackfruit peel at 300 °C for removal of different cationic pollutants, and characterized by element analysis, FTIR, SEM-EDS, XRD, XPS and so on. MgFe₂O₄ was generated without external base and a 19.42 emu/g saturation magnetization was achieved. Simultaneously, iron oxides and oxygen containing groups were introduced. The magnetic biochar exhibited 61.30 mg/g, 129.61 mg/g, and 1238.30 mg/g adsorption capacities for Cu²⁺, methylene blue (MB), and malachite green (MG) at 25 °C, respectively, and remarkably surpassed the corresponding pristine biochar. The adsorption of MB and MG was mainly realized by electrostatic interaction, hydrogen bonding, complexation, and π-π electron-donor-acceptor interaction, and that of Cu²⁺ was attributed to electrostatic interaction, hydrogen bonding, and complexation.