Shrimp waste-derived porous carbon adsorbent: Performance, mechanism, and application of machine learning

Solid shrimp waste derived nanoporous carbon as an alternative bio-sorbent for oxytetracycline removal from aquaculture wastewater

Recently, it has been critical to effectively remove oxytetracycline (OTC) from aquaculture wastewater before releasing into the environment. The adsorption process is recognized as an efficient pathway for removing OTC since it is a simple, stable, and cost-effective method. This study aims to develop nanoporous carbon entirely from shrimp waste (SW) via hydrothermal carbonization assisted with KOH activation. Existing KOH significantly increases the porosity of SW nanoporous carbon. The optimal SW porous carbon was obtained using 5 wt%KOH for activation, which had the largest surface area of 679.51 m2/g with the total pore volume of 0.458 cm3/g. Moreover, the SW porous carbon with the highest porosity was selected for the OTC adsorption. The Langmuir isotherm model and the pseudo-second-order kinetic model match the experimental data, implying that the adsorption mechanism is mono-layered adsorption due to micropores by chemisorption interaction. The adsorption capacity significantly improved by increasing the dosage of SW nanoporous carbon. The SW nanoporous carbon adsorption for OTC is primarily regulated by pore filling affected by hydrogen bonding, and π-π* interaction also plays a significant role. The SW nanoporous carbon showed an efficient OTC adsorption after 5 regeneration cycles. This work demonstrates biomass waste recycling and emphasizes the potential of aquatic food processing waste-derived nanoporous carbon for antibiotic adsorption.

Seafood waste derived carbon nanomaterials for removal and detection of food safety hazards

Nanobiotechnology and the engineering of nanomaterials are currently the main focus of many researches. Seafood waste carbon nanomaterials (SWCNs) are a renewable resource with large surface area, porous structure, high reactivity, and abundant active sites. They efficiently adsorb food contaminants through π-π conjugated, ion exchange, and electrostatic interaction. Furthermore, SWCNs prepared from seafood waste are rich in N and O functional groups. They have high quantum yield (QY) and excellent fluorescence properties, making them promising materials for the removal and detection of pollutants. It provides an opportunity by which solutions to the long-term challenges of the food industry in assessing food safety, maintaining food quality, detecting contaminants and pretreating samples can be found. In addition, carbon nanomaterials can be used as adsorbents to reduce environmental pollutants and prevent food safety problems from the source. In this paper, the types of SWCNs are reviewed; the synthesis, properties and applications of SWCNs are reviewed and the raw material selection, preparation methods, reaction conditions and formation mechanisms of biomass-based carbon materials are studied in depth. Finally, the advantages of seafood waste carbon and its composite materials in pollutant removal and detection were discussed, and existing problems were pointed out, which provided ideas for the future development and research directions of this interesting and versatile material. Based on the concept of waste pricing and a recycling economy, the aim of this paper is to outline current trends and the future potential to transform residues from the seafood waste sector into valuable biological (nano) materials, and to apply them to food safety.

Catalytically Active Carbon for Oxygen Reduction Reaction in Energy Conversion: Recent Advances and Future Perspectives

The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new-generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass-derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass-derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass-derived CAC-based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass-derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass-derived CAC-based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass-derived CAC electrocatalysis and electric energy storage.

Adsorption of PFAS onto secondary microplastics: A mechanistic study

Microplastics (MPs) are abundant in aquatic systems. The ecological risks of MPs may arise from their physical features, chemical properties, and/or their ability to concentrate and transport other contaminants, such as per- and polyfluoroalkyl substances (PFAS). PFAS have been extracted from MPs found in natural waters. Still, there needs to be a mechanistic investigation of the effect of PFAS chemistry and water physicochemical properties on how PFAS partition onto secondary MPs. Here, we studied the influence of pH, natural organic matter (NOM), ionic strength, and temperature on the adsorption of PFAS on MPs generated from PET water bottles. The adsorption of PFAS to the MPs was thermodynamically spontaneous at 25 °C, based on Gibb's free energy (ΔG = -16 to -23 kJ/mol), primarily due to increased entropy after adsorption. Adsorption reached equilibrium within 7-9 h. Hence, PFAS will partition to the surface of secondary PET MPs within hours in fresh and saline waters. Natural organic matter decreased the capacity of secondary PET MPs for PFAS through electrosteric repulsion, while higher ionic strength favored PFAS adsorption by decreasing electrostatic repulsion. Increased pH increased electrostatic repulsion, which negated PFAS adsorption. The study provides fundamental information for developing models to predict interactions between secondary MPs and PFAS.

Machine learning applications for biochar studies: A mini-review

Biochar is a promising carbon sink whose application can assist in reducing carbon emissions. Development of this technology currently relies on experimental trials, which are time-consuming and labor-intensive. Machine learning (ML) technology presents a potential solution for streamlining this process. This review summarizes the current research on ML's applications in biochar production, characterization, and applications. It briefly explains commonly used machine learning algorithms and discusses prospects and challenges. A hybrid model that combines ML with mechanism-based analysis could be a future trend, addressing the ML's black-box nature. While biochar studies have adopted ML technology, current works mostly use lab-scale data for model training. Further work is needed to develop ML models based on pilot or industrial-scale data to realize the use of ML techniques for the field application of biochar.

Production of MgFe2O4/activated carbons derived from a harmful grass Cynodon dactylon and their utilization for ciprofloxacin removal

Cynodon dactylon, an invasive species, exhibits its robust adaptability, reproduction and nutrient regime against the local species. Taking advantage of this harmful grass as a raw precursor to produce valuable materials for wastewater treatment has paid much attention. Herein, we report on the fabrication of Cynodom dactylon derived MgFe2O4@AC with a main goal of effective removal of ciprofloxacin antibiotic from water. Our findings showed that MgFe2O4@ACK1 composites attained mesoporous textures, high specific surface areas (884.3-991.6 m2 g-1), and MgFe2O4-20%@ACK1 was the most effective with a very high removal efficiency of 96.7%. The Elovich model was suitable for describing the kinetic of adsorption with (Radj)2 of 0.9988. Meanwhile, the isotherm data obeyed the Langmuir model corresponding to (Radj)2 of 0.9993. Qmax value of MgFe2O4-20%@ACK1 was determined at 211.67 mg g-1. The proposed adsorption mechanism primarily comprises five routes as follows, (i) pore-filling, (ii) π-π interaction, (iii) electrostatic interaction, (iv) hydrogen bonding, and (v) hydrophobic interaction. MgFe2O4-20%@ACK1 adsorbent could reuse with three cycles. We recommend that MgFe2O4/ACs derived from Cynodom dactylon could be high-efficiency adsorbents for the elimination of antibiotics.

Sustainable wastewater purification with crab shell-derived biochar: Advanced machine learning modeling & experimental analysis

Detoxifying ecologically persistent dyes is vital for environmental and human well-being. Herein, crabshell waste is transformed into porous carbon (CB900) through pyrolysis, achieving a remarkable removal rate of 90.5% (CR-RR) and adsorption capacity (∼256.36 mg g-1, qCR). Employing XGBoost modeling, with a robust R2 ∼0.996, proved its superiority over others in predicting CR adsorption. PSO-XGB optimization led to an optimal configuration: 0.051 g adsorbent, 460.56 mg L-1 CR concentration, pH 3.16, and a 94.01 min contact time, resulting in 68.39% CR-RR and 822.15 mg g-1 qCR, simultaneously; sensitivity analysis unveiled the pivotal role of pH and adsorbent dose. CB900 exhibited physical, spontaneous, endothermic following both Langmuir and Freundlich isotherms. Remarkably, CB900 effectively eliminated various contaminants, including chromium and sulfasalazine antibiotic. Pilot-scale CB900 production cost via pyrolysis was $8.5/kg, a fraction of commercial powdered activated carbon, underscoring its economic viability and potential as a sustainable solution for the elimination of toxic contaminants from aqueous environments.

Effects of perfluoroalkyl substances on the operational efficiency, microbial communities, and key metabolic pathways of constructed rapid infiltration system with coke as filler layer

Influences of perfluoroalkyl substances on the performance and microbial metabolic pathways of constructed rapid infiltration systems are not fully understood. In this study, wastewater containing different concentrations of perfluorooctanoic acid (PFOA)/perfluorobutyric acid (PFBA) was treated in constructed rapid infiltration systems with coke as filler. The addition of 5 and 10 mg/L PFOA inhibited the removal of chemical oxygen demand (COD) (80.42%, 89.27%), ammonia nitrogen (31.32%, 41.14%), and total phosphorus (TP) (43.30%, 39.34%). Meanwhile, 10 mg/L PFBA inhibited TP removal of the systems. Based on X-ray photoelectron spectroscopy, the percentages of F^- within the PFOA and PFBA groups were 12.91% and 48.46%, respectively. PFOA transformed Proteobacteria (71.79%) into the dominant phyla of the systems, whereas PFBA enriched Actinobacteria (72.51%). The PFBA up-regulated the coding gene of 6-phosphofructokinase by 14.44%, whereas PFOA down-regulated it by 4.76%. These findings provide insights into the toxicity of perfluoroalkyl substances on constructed rapid infiltration systems.

A Critical Review of Snail Shell Material Modification for Applications in Wastewater Treatment

Sea material is becoming increasingly popular and widely used as an adsorbent in wastewater treatment. Snail shell, a low-cost and natural animal waste material, has been shown to have a high calcium content (>99%) and a large potential surface area for the development of sustainable adsorbents. This paper presents a novel synthesis of methods for using snail shell absorbent materials in the treatment of wastewater containing heavy metals, textile dyes, and other organic substances. Modified biochar made from snail shells has gained popularity in recent years due to its numerous benefits. This paper discusses and analyzes modification methods, including impregnating with supplements, combining other adsorbents, synthesis of hydroxyapatite, co-precipitation, and the sol-gel method. The analysis of factors influencing adsorption efficiency revealed that pH, contact time, temperature, initial concentration, and adsorbent dose all have a significant impact on the adsorption process. Future research directions are also discussed in this paper as a result of presenting challenges for current snail adsorbents.