Synthesis of carbon-based nanomaterials and their application in pollution management

Current trends in textile wastewater treatment-bibliometric review

A bibliometric study using 1992 to 2021 database of the Science Citation Index Expanded was carried out to identify which are the current trends in textile wastewater treatment research. The study aimed to analyze the performance of scholarly scientific communications in terms of yearly publications/citations, total citations, scientific journals, and their categories in the Web of Sciences, top institutions/countries and research trends. The annual publication of scientific articles fluctuated in the first ten years, with a steady decrease for the last twenty years. An analysis of the most common terms used in the authors' keywords, publications' titles, and KeyWords Plus was carried out to predict future trends and current research priorities. Adsorbent nanomaterials would be the future of wastewater treatment for decoloration of the residual dyes in the wastewater. Membranes and electrolysis are important to demineralize textile effluent for reusing wastewater. Modern filtration techniques such as ultrafiltration and nanofiltration are advanced membrane filtration applications.

Cellulose acetate/polyurethane blend as support matrix with high optical transparency and improved mechanical properties for photocatalyst CeO2 nanoparticles immobilization

Advanced manufacturing technologies for efficient catalytic materials have triggered the rational design of catalysts as well as extensive investigation into preparative methodologies. Herein, we report the preparation of new versatile cellulose acetate/polyurethane (CA/PU) blends for efficient immobilization of CeO2 nanoparticles, the appropriate composition of polymer mixture being chosen after rigorous analysis (SEM, FTIR, optical, mechanical). The band gap energy for hybrid films ranged between 3.02 eV and 2.05 eV, the lowest value being measured for the film with Co-doped CeO2 NPs (B3 film). The best results in photodegradation of methylene blue under visible-light irradiation was attained after 50 min for B3 film (rate constant k = 45.34× 10-3 min-1), while the total mineralization of MB in the same conditions as evaluated by HPLC-ESI MS and TOC analyses was achieved after 90 min. Effect of co-ions (SO42-, Cl- or NO3-) on photocatalytic performance was studied, and scavenger tests were used to identify the active species involved in the photocatalytic mechanism. Also, the photocatalytic efficiency of B3 sample was tested for rhodamine B, metronidazole and 4-nitrophenol degradation. Evaluation of the stability and integrity of hybrid film after 5 catalysis cycles reveal that the photocatalytic potential is retained with no substantial structural changes.

Aggregation of biochar nanoparticles and the impact on bisphenol A sorption: Experiments and molecular dynamics simulations

The unique properties and environmental implications of biochar nanoparticles (BNPs) have attracted increasing attention. The abundant functional groups and aromatic structures in BNPs may promote the aggregation of BNPs, but the mechanism and implications of this aggregation process remain unclear. Thus, this study investigated the aggregation of BNPs and the sorption of bisphenol A (BPA) on BNPs by combining experimental investigations with molecular dynamics simulations. As the concentration of BNP increased from 100 mg/L to 500 mg/L, the particle size increased from approximately 200 nm to 500 nm, and the exposed surface area ratio in the aqueous phase decreased from 0.46 to 0.05, which confirmed the aggregation of BNPs. The sorption of BPA on BNPs decreased with increasing BNP concentration in both the experiments and molecular dynamics simulations because of BNP aggregation. According to a detailed analysis of the BPA molecules adsorbed on BNP aggregates, the sorption mechanisms were hydrogen bonding, hydrophobic effect, and π-π interactions, which were driven by aromatic rings and O- and N-containing functional groups. The aggregation of BNPs embedded some functional groups in the aggregates and thus inhibited sorption. Interestingly, the steady configuration of the BNP aggregates in the molecular dynamics simulations (2000 ps relaxation) also determined the apparent BPA sorption. BPA molecules were adsorbed in the V-shaped interlayers of the BNP aggregates that acted as semi-closed pores, but could not be adsorbed in the parallel interlayers because of their small layer spacing. This study can provide theoretical guidance for the application of BNPs in pollution control and remediation.

A rationale for the rapid extraction of ultra-low-level uranyl ions in simulated bioassays regulated by Mn-dopants over magnetic nanoparticles

Although the sorption of uranyl ions and other heavy metal ions over magnetic nanoparticles is well reported, the parameters governing the sorption process over the magnetic nanoparticles have not been clearly enumerated. However, to increase the efficiency of the sorption over the surface of these magnetic nanoparticles, it is essential to understand the different structural parameters that are involved in the sorption process. The sorption of uranyl ions and other competitive ions in simulated urine samples at different pH was effectively accomplished over magnetic nanoparticles of Fe₃O₄ (MNPs) and Mn-doped Fe₃O₄ (Mn-MNPs). The MNPs and Mn-MNPs were synthesized using an easily modified co-precipitation method and were thoroughly characterised using several techniques, such as XRD, HRTEM, SEM, zeta potential, and XPS. The substitutional doping of Mn (1 to 5 at%) in the Fe₃O₄ lattice (Mn-MNPs) showed better sorption ability as compared to that of MNPs. The sorption properties of these nanoparticles were mainly correlated with the different structural parameters to understand the roles of surface charge and different morphological parameters. The interaction centres over the surface of MNPs with the uranyl ions were designated and the effects of ionic interactions with uranyl ions for these sites were calculated. Extensive XPS, ab initio calculations and zeta potential studies have provided deep insights into the different aspects that play key roles in the sorption process. These materials showed one of the best K_d values (∼3 × 10⁶ cm³) in a neutral medium with very low t_1/2 values (∼0.9 min). The fast sorption kinetics (very low t_1/2) makes them amongst the best sorption materials for uranyl ions and optimal for the quantification of ultra-low-level uranyl ions in simulated bioassays.

Carbon-Based Nanomaterials for Catalytic Wastewater Treatment: A Review

Carbon-based nanomaterials (CBM) have shown great potential for various environmental applications because of their physical and chemical properties. The unique hybridization properties of CBMs allow for the tailored manipulation of their structures and morphologies. However, owing to poor solar light absorption, and the rapid recombination of photogenerated electron-hole pairs, pristine carbon materials typically have unsatisfactory photocatalytic performances and practical applications. The main challenge in this field is the design of economical, environmentally friendly, and effective photocatalysts. Combining carbonaceous materials with carbonaceous semiconductors of different structures results in unique properties in carbon-based catalysts, which offers a promising approach to achieving efficient application. Here, we review the contribution of CBMs with different dimensions, to the catalytic removal of organic pollutants from wastewater by catalyzing the Fenton reaction and photocatalytic processes. This review, therefore, aims to provide an appropriate direction for empowering improvements in ongoing research work, which will boost future applications and contribute to overcoming the existing limitations in this field.

Recent progresses, challenges, and opportunities of carbon-based materials applied in heavy metal polluted soil remediation

The application of carbon-based materials (CBMs) for heavy metal polluted soil remediation has gained growing interest due to their versatile properties and excellent remediation performance. Although the progresses on applications of CBMs in removing heavy metal from aqueous solution and their corresponding mechanisms were well known, comprehensive review on applications of CBMs in heavy metal polluted soil remediation were less identified. Therefore, this review provided insights into advanced progresses on utilization of typical CBMs including biochar, activated carbon, graphene, graphene oxide, carbon nanotubes, and carbon black for heavy metal polluted soil remediation. The mechanisms of CBM remediation of heavy metals in soil were summarized, mainly including physical adsorption, precipitation, complexation, electrostatic interaction, and cationic-π coordination. The key factors affecting the remediation effect include soil pH, organic matter, minerals, microorganisms, coexisting ions, moisture, and material size. Disadvantages of CBMs were also included, such as: potential health risks, high cost, and difficulty in achieving co-passivation of anions and cations. This work will contribute to our understanding of current research advances, challenges, and opportunities for CBMs remediation of heavy metal-contaminated soils.

Bioinorganic Nanoparticles for the Remediation of Environmental Pollution: Critical Appraisal and Potential Avenues

Nowadays, environmental pollution has become a critical issue for both developed and developing countries. Because of excessive industrialization, burning of fossil fuels, mining and exploration, extensive agricultural activities, and plastics, the environment is being contaminated rapidly through soil, air, and water. There are a variety of approaches for treating environmental toxins, but each has its own set of restrictions. As a result, various therapies are accessible, and approaches that are effective, long-lasting, less harmful, and have a superior outcome are extensively demanded. Modern research advances focus more on polymer-based nanoparticles, which are frequently used in drug design, drug delivery systems, environmental remediation, power storage, transformations, and other fields. Bioinorganic nanomaterials could be a better candidate to control contaminants in the environment. In this article, we focused on their synthesis, characterization, photocatalytic process, and contributions to environmental remediation against numerous ecological hazards. In this review article, we also tried to explore their recent advancements and futuristic contributions to control and prevent various pollutants in the environment.

Modified biochar: synthesis and mechanism for removal of environmental heavy metals

With social progress and industrial development, heavy metal pollution in water and soils environment is becoming more serious. Although biochar is a low-cost and environmentally friendly adsorbent for heavy metal ions, its adsorption and immobilization efficiency still need to be improved. As an upgraded version of biochar, modified biochar has attracted extensive attention in the scientific community. This review summarized the recent research progress on the treatment methods on heavy metal pollutants in water and soils using biochar. The features and advantages of biochar modification techniques such as physical modification, chemical modification, biological modification and other categories of biochar were discussed. The mechanism of removing heavy metals from soil and water by modified biochar was summarized. It was found that biochar had better performance after modification, which provided higher surface areas and more functional groups, and had enough binding sites to combine heavy metal ions. Biochar is a very promising candidate for removing heavy metals in environment. Furthermore, some high valent metal ions could be reduced to low valent metals, such as Cr(VI) reduction to Cr(III), and form precipitates on biochar by in-situ sorption-reduction-precipitation strategy. However, it is still the direction of efforts to develop high-efficiency modified biochar with low-cost, high sorption capacity, high photocatalytic performance, environmentally friendly and no secondary pollution in future.

Facile Conversion of Polystyrene Waste into an Efficient Sorbent for Water Purification

In this work, we convert a plastic waste, i.e., polystyrene (PS), into a sorbent by a simple sulfonation process. The sulfonation time was optimized and the structures of the resulting sulfonated polystyrene (SPS) was characterized by field emission scanning electron microscopy, energy-dispersive X-ray and contact angle tests. The results showed that the sulfonation time of 7 h can introduce abundant sulfonic groups and preserve the self-standing structure. Additionally, the SPS has a three-dimensional porous structure and hydrophilic surface because of the presence of numerous sulfonic groups, which could serve as effective binding sites for immobilizing varying pollutants. Furthermore, as a proof-of-concept, the adsorption performance of the SPS foams was evaluated using three pollutants, namely Pb²⁺, lysozyme and methylene blue. The adsorption isotherms were fitted by the Langmuir and Freundlich models, while the kinetics of the adsorption processes were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. It was found that the adsorption isotherms of Pb²⁺ and lysozyme can be better described by the Langmuir model, leading to maximum equilibrium adsorption uptakes of 10.5 and 15.7 mg g⁻¹ for the adsorption of Pb²⁺ and lysozyme, respectively. Importantly, the pollutant-saturated SPS is readily regenerated by acid washing, and the recovered sorbents exhibit outstanding cyclic performance. The abundant availability of feedstock, facile preparation and regeneration processes render the SPS foams a promising sorbent for practical applications.