Evaluation of Removal Efficiency of Ni(II) and 2,4-DCP Using in Situ Nitrogen-Doped Biochar Modified with Aquatic Animal Waste

Adsorption and photocatalytic degradation of 2,4-dicholrophenol using surgical mask derived SMAC-Fe2O3 composite; adsorption isotherms, kinetics, thermodynamics

Hybrid material of surgical mask activated carbon (SMAC) and Fe2O3 (SMAC-Fe2O3) composite was prepared by simple co-precipitation method and used as potential material for the remediation of 2,4-dicholrophenol (2,4-DCP). The XRD patterns exhibited the presence of SMAC and Fe2O3, FTIR spectrum showed the FeO-carbon stretching at the wavenumber from 400 to 550 cm-1. UV-Vis DRS results showed the band gap was 1.97 eV and 2.05 eV for SMAC-Fe2O3 and Fe2O3, respectively. The SEM images revealed that the Fe2O3 doped onto the fiber morphology of SMAC. The outcomes of the BET examination exhibited a surface area of 195 m2/g and a pore volume of 0.2062 cm3/g for the SMAC/Fe2O3 composite. The batch mode study shows the maximum adsorption and photocatalytic degradation efficacies which were 97% and 78%, respectively. The experimental data was studied with both linear and nonlinear adsorption isotherm and kinetics models. The nonlinear Langmuir isotherm and pseudo-second-order kinetics (PSOK) models have well fit compared with other models. The Langmuir maximum adsorption capacity (qmax) was found 161.60 mg/g. Thermodynamic analysis shows that the 2,4-DCP adsorption onto SMAC-Fe2O3 was a spontaneous and exothermic process. The PSOK assumes that the adsorption process was chemisorption. The photocatalytic degradation rate constant of 2,4-DCP was calculated using pseudo-first-order kinetics (PFOK) and the rate constant for SMAC-Fe2O3 and Fe2O3 were 0.859 × 10-2 min-1 and 0.616 × 10-2 min-1, correspondingly. In addition, the obtained composite exhibited good reusability after a few cycles. These results confirmed that SMAC-Fe2O3 composite is an effective adsorbent and photocatalyst for removing 2,4-DCP pollutants.

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Immobilizing white-rot fungi laccase: Toward bio-derived supports as a circular economy approach in organochlorine removal

Despite their high persistence in the environment, organochlorines (OC) are widely used in the pharmaceutical industry, in plastics, and in the manufacture of pesticides, among other applications. These compounds and the byproducts of their decomposition deserve attention and efficient proposals for their treatment. Among sustainable alternatives, the use of ligninolytic enzymes (LEs) from fungi stands out, as these molecules can catalyze the transformation of a wide range of pollutants. Among LEs, laccases (Lac) are known for their efficiency as biocatalysts in the conversion of organic pollutants. Their application in biotechnological processes is possible, but the enzymes are often unstable and difficult to recover after use, driving up costs. Immobilization of enzymes on a matrix (support or solid carrier) allows recovery and stabilization of this catalytic capacity. Agricultural residual biomass is a passive environmental asset. Although underestimated and still treated as an undesirable component, residual biomass can be used as a low-cost adsorbent and as a support for the immobilization of enzymes. In this review, the adsorption capacity and immobilization of fungal Lac on supports made from residual biomass, including compounds such as biochar, for the removal of OC compounds are analyzed and compared with the use of synthetic supports. A qualitative and quantitative comparison of the reported results was made. In this context, the use of peanut shells is highlighted in view of the increasing peanut production worldwide. The linkage of methods with circular economy approaches that can be applied in practice is discussed.

Remediation of cadmium-contaminated soil by micro-nano nitrogen-doped biochar and its mechanisms

Cadmium-contaminated soils are an urgent problem that needs to be solved in many countries and regions. In this study, a new heavy metal passivator, micro-nano nitrogen-doped biochar (Nm-NBC), was prepared by introducing nitrogen into biochar. Soybean was used as an experimental plant to compare the effects of corn straw biochar (CBC, not modified), ammonium chloride modified corn straw biochar (NBC), and micro-nano nitrogen-doped biochar (Nm-NBC) on the remediation of Cdcontaminated soil. The results showed that the biomass of soybean, pH, organic matter, and total nitrogen content of the Cd-contaminated soil significantly increased, and the available Cd in soil significantly reduced (P < 0.05) when CBC, NBC, and Nm-NBC were added. The effect was as follows: Nm-NBC > NBC > CBC; Nm-NBC had the best result. When 1% Nm-NBC added to the soil, the Cd content in beans reduced by 68.09%. BET, FTIR, XPS, and SEM were used to analyze the characteristics of Nm-NBC and its mechanisms in the remediation of Cd-contaminated soils. The results showed that Nm-NBC had larger specific surface area and abundant functional groups; -COOH and graphitic nitrogen in Nm-NBC can form Cd-O bond and Cd-π with Cd(II) in the soil. Therefore, Nm-NBC prepared by introducing nitrogen into biochar has a promising application in the remediation of Cd-contaminated soil.

Porous adsorbent derived from acid activation of food waste biochar: A sustainable approach for novel removal chlorophenol in wastewater

In this study, porous biochar (PBC) was prepared by acid activation of biochar derived from food waste (FWBC) and used as a suitable approach for the removal of 4-chlorophenol (CP) in wastewater. The characterization of PBC and the influent of different experimental conditions are determined. After the acid activation process, the surface area, porosity, and functional groups of PBC were developed. The removal performances of CP (1 mg/L) by PBC and FWBC were archived at 97.8 and 82.1%, respectively. Adsorption kinetics and isotherms of CP were followed by the second-order and Langmuir models, respectively. The maximum capacities of CP uptake onto mono-layer of FWBC and PBC based on the Langmuir model were determined at 79.8 and 108.7 mg/g, respectively. Besides, PBC could remove more than 89% CP from wastewater within 45 min of reaction time and it is suitable to reuse 8 times with over 60% adsorption efficiency of CP. In addition, the adsorption mechanism and environmental impact were discussed in detail. This work could bring a sustainable approach to the treatment of CP in wastewater as well as the management of food waste in Vietnam.

Effect of Surface Modification by Oxygen-Enriched Chemicals on the Surface Properties of Pine Bark Biochars

Sustainable waste utilization techniques are needed to combat the environmental and economic challenges faced worldwide due to the rising population. Biochars, due to their unique surface properties, offer opportunities to modify their surface to prepare application-specific materials. The aim of this research is to study the effects of biochar surface modification by oxidizing chemicals on biochar properties. Pine bark biochar was modified with sulfuric acid, nitric acid, hydrogen peroxide, ozone, and ammonium persulfate. The resulting biochars’ pH, pH at the point of zero charges, and concentration of acidic and basic sites were determined using laboratory experimentation. Instrumental techniques, such as infrared and X-ray photoelectron spectroscopy, were also obtained for all biochar samples. X-ray photoelectron spectra showed that oxygen content increased to 44.5%, 42.2%, 33.8%, 30.5%, and 14.6% from 13.4% for sulfuric acid, ozone, nitric acid, hydrogen peroxide, and ammonium persulfate, respectively. The pH at the point of zero charges was negatively correlated with the difference in concentration of acidic and basic sites in biochar samples, as well as the summation of peak components representing C=O double bonds and carboxylic groups. The results suggest that designer biochars can be prepared by understanding the interaction of oxygenated chemicals with biochar surfaces.

Novel assembly of BiVO4@N-Biochar nanocomposite for efficient detoxification of triclosan

The wide spread of antibacterial and antifungal agents demands in growing multifunctional materials to completely eliminate these organic contaminants in water. BiVO₄ (Bismuth vanadate) is a superior catalyst under visible light but suffers with high photoelectron-hole pair recombination rate and poor adsorption capacity which limits its efficiency. Addition of N-doped Biochar (N-Biochar) to BiVO₄ with large specific surface area and high conductivity are anticipated to overcome the problem and promote the catalytic performance. Thus, the present study developed a simple hydrothermal method to prepare BiVO₄@N-Biochar catalyst for efficient detoxification of Triclosan (TCS). The morphological analysis results suggested that BiVO₄ particles were evenly distributed on carbon surface amongst the N-Biochar matrix. Within 60 min of visible light irradiation, nearly 94.6% TCS degradation efficiency was attained by BiVO₄@N-Biochar (k = 0.02154 min^-1) while only 56.7% was attained with pure BiVO₄ (k = 0.00637 min^-1). In addition, LC-MS/MS technique was utilized to determine the TCS degradation products generation in the photodegradation process and pathway was proposed. Furthermore, the E. coli (Escherichia coli) colony forming unit assay was used to determine the biotoxicity of the degradation products in which 72.3 ± 2.6% of detoxification efficiency was achieved and suggested a substantial reduction in biotoxicity during the photodegradation.

Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose

Biochar derived from nitrogen-rich pyrolysis of biomass can be used as a soil conditioner, but it contains a large amount of environmental persistent free radicals (EPFRs). EPFRs are a newly identified environmentally harmful substance, and the detection and research on EPFRs in nitrogen-rich pyrolyzed char is lacking. Biochars prepared from cellulose-urea mixtures at different temperatures, residence times, and urea ratios were analyzed in this study. EPFRs in biochar prepared at 500 °C had the highest spin concentrations. Substituted aromatic compounds were the precursors to the EPFRs. The types of EPFRs in biochars shifted from oxygen-centered at 400 °C to carbon- and oxygen-centered in the 450-600 °C range due to a reduction in oxygen-containing functional groups. Residence time experiments showed that most EPFRs formed in the first 5 min of pyrolysis. C was the main element used for the formation of EPFRs, while N content was negatively correlated with the concentration of EPFRs. Pyrolysis temperature was the key factor determining the types of EPFRs produced, while proportion of urea only affected the concentrations of EPFRs and not type. The results of this study are of great significance for understanding the environmental behavior of common EPFRs in nitrogen-rich biochar.

Competitive adsorption of methanol co-solvent and dioctyl phthalate on functionalized graphene sheet: Integrated investigation by molecular dynamics simulations and quantum chemical calculations

HYPOTHESIS

Organic co-solvents, which are universally employed in adsorption studies of hydrophobic organic chemicals (HOCs), can inhibit HOC adsorption by competing for active sites on the adsorbent. The adsorbent structure can influence co-solvent interference of HOC adsorption; however, this effect remains unclear, leading to an incomplete understanding of the adsorption mechanism.

EXPERIMENTS

In this study, dioctyl phthalate (DOP) was used to investigate competitive adsorption on functionalized graphene sheet in a water-methanol co-solvent system through molecular dynamics simulations and quantum chemical calculations.

FINDINGS

The simulations showed that the functional groups in the graphene defects had a strong adsorption affinity for methanol. The adsorbed methanol occupied a large number of active sites at the graphene center, thereby weakening DOP adsorption. However, the methanol adsorbed at the graphene edges could not compete with DOP for the active sites. -COOH had the strongest binding affinity for methanol among the functional groups and thus predominantly controlled the interaction between graphene and methanol. This study makes an innovative contribution toward understanding the competitive adsorption of methanol and DOP on functionalized graphene sheet, especially in visualizing the competition for active sites, and provides theoretical guidance for the removal of HOCs and practical application of graphene.

Removal of Tetracycline from Water Using Activated Carbon Derived from the Mixture of Phragmites australis and Waterworks Sludge

Sludge-based activated carbon with doped Phragmites australis was prepared using an environment-friendly method to treat waterworks sludge (WS) and obtain an economical adsorbing material for tetracycline (TC) elimination. For the WS, P. australis was used as an additive to optimize the preparation of activated carbon. Optimum preparation conditions were as follows: activation temperature, 600 °C; ZnCl₂ concentration, 3 mol/L; activation time, 50 min; impregnation ratio (weight of mix sample: weight of ZnCl₂) of 1:2.5; and the mixed ratio of P. australis with WS, 40%. The obtained activated carbon owned well-developed Brunauer-Emmett-Teller surface area (949.90 m²/g). The acidic and basic functional groups were improved to 0.762 and 0.016 mmol/g, respectively. The pseudo-second-order kinetic and Freundlich isotherm equations were more suitable models to simulate adsorption with the maximum adsorption capacity of 153.4 mg/g. According to the thermodynamic parameters, the adsorption process was spontaneous and endothermic. Electrostatic interaction, hydrogen bonding formation, and ion complexation adsorption mechanisms were the mechanisms underlying the adsorption of TC.