Sustainable nanotechnology based wastewater treatment strategies: achievements, challenges and future perspectives

Re-vitalizing Wastewater: Nutrient Recovery and carbon capture through Microbe-Algae synergy using Omics-Biology

Increasing amounts of wastewater is the most pervasive and challenging environmental problem globally. Conventional treatment methods are costly and entail huge energy and carbon consumption and greenhouse gas emissions. Owing to their unique ability of carbon capturing and resource recovery, microalgae-microbiome based treatment is a potential approach and is widely used for carbon-neutral wastewater treatment. Microalgae-bacteria synergy (i.e., the functionally beneficial microbial synthetic communities) performs better and enhances carbon-sequestration and nutrient recovery from wastewater treatment plants. This review presents a comprehensive information regarding the potential of microalgae-microbiome as a sustainable agent for wastewater and discusses synergistic approaches for effective nutrient removal. Moreover, this review discusses, the role of omics-biology and Insilco approaches in unravelling and understanding the algae-microbe synergism and their response toward wastewater treatment. Finally, it discusses various microbiome engineering approaches for developing the effective microalgae-bacteria partners for carbon sequestration and nutrient recovery from wastewater, and summarizes future research perspectives on microalgae-microbiome based bioremediation.

An overview on the key advantages and limitations of batch and dynamic modes of biosorption of metal ions

Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.

Composite RGO/Ag/Nanosponge Materials for the Photodegradation of Emerging Pollutants from Wastewaters

Some composite materials have been prepared, constituted by a cyclodextrin-bis-urethane-based nanosponge matrix in which a reduced graphene oxide/silver nanoparticles photocatalyst has been dispersed. Different chain extenders were employed for designing the nanosponge supports, in such a way as to decorate their hyper-cross-linked structure with diverse functionalities. Moreover, two different strategies were explored to accomplish the silver loading. The obtained systems were successfully tested as catalysts for the photodegradation of emerging pollutants such as model dyes and drugs. Enhancement of the photoactive species performance (up to nine times), due to the synergistic local concentration effect exerted by the nanosponge, could be assessed. Overall, the best performances were shown by polyamine-decorated materials, which were able to promote the degradation of some particularly resistant drugs. Some methodological issues pertaining to data collection are also addressed.

Revolutionizing soil heavy metal remediation: Cutting-edge innovations in plant disposal technology

Soil contamination with heavy metals has emerged as a global environmental threat, compromising agricultural productivity, ecosystem integrity, and human health. Conventional remediation techniques often fall short due to high costs, operational complexities, and environmental drawbacks. Plant-based disposal technologies, including biochar, phytometallurgy, and phrolysis, have emerged as promising solutions in this regard. Grounded in a novel experimental framework, biochar is studied for its dual role as soil amendment and metal adsorbent, while phytometallurgy is explored for its potential in resource recovery and economic benefits derived from harvested metal-rich plant biomass. Pyrolysis, in turn, is assessed for transforming contaminated biomass into value-added products, thereby minimizing waste. These plant disposal technologies create a circular model of remediation and resource utilization that holds the potential for application in large-scale soil recovery projects, development of environmentally friendly agro-industries, and advancement in sustainable waste management practices. This review mainly discussed cutting-edge plant disposal technologies-biochar application, phytometallurgy, and pyrolysis-as revolutionary approaches to soil heavy metal remediation. The efficacy, cost-effectiveness, and environmental impact of these innovative technologies are especially evaluated in comparison with traditional methods. The success of these applications could signal a paradigm shift in how we approach both environmental remediation and resource recovery, with profound implications for sustainable development and circular economy strategies.

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.

Novel insights into carbon nanomaterials enhancing anammox for nitrogen removal: Effects and mechanisms

Carbon nanomaterials (CNMs) possess the properties including large specific surface area, high porosity, and stable chemical structures, presenting significant application advantages in wastewater treatment. Indeed, CNMs are considered to be added to anammox systems to strengthen anammox function, especially to resolve the challenge of anammox technology, i.e., the slow growth rate of anammox bacteria, as well as its high environmental sensitivity. This paper systematically reviews the promotion effects and mechanisms of CNMs on the nitrogen removal performance of anammox system. Among the zero-, one-, and two-dimensional CNMs, two-dimensional CNMs have best promoting effect on the nitrogen removal performance of anammox system due to its excellent conductivity and abundant functional groups. Then, the promotion effects of CNMs on anammox process are summarized from the perspective of anammox activity and bacteria abundance. Furthermore, CNMs not only enhance the anammox process, but also stimulate the coupling of denitrification pathways with anammox, as well as the improvement of system operational stability (alleviating the inhibitions of low temperature and pH fluctuation), thus contributing to the promoted nitrogen removal performance. Essentially, CNMs are capable of facilitating microbial immobilization and electron transfer, which favor to improve the efficiency and stability of anammox process. Finally, this review highlights the gap in knowledge and future work, aiming to provide a deeper understanding of how CNMs can strengthen the anammox system and provide a novel perspective for the engineering of the anammox process.

Carbon nanotube-wastewater treatment nexus: Where are we heading to?

Water treatment is crucial in solving the rising people's appetite for water and global water shortages. Carbon nanotubes (CNTs) have considerable promise for water treatment because of their adjustable and distinctive arbitrary, physical, as well as chemical characteristics. This illustrates the benefits and risks of integrating CNT into the traditional water treatment resource. Due to their outstanding adsorbent ability and chemical and mechanical properties, CNTs have gained global consideration in environmental applications. The desalination and extraction capability of CNT were improved due to chemical or physical modifications in pure CNTs by various functional groups. The CNT-based composites have many benefits, such as antifouling performance, high selectivity, and increased water permeability. Nevertheless, their full-scale implementations are still constrained by their high costs. Functionalized CNTs and their promising nanocomposites to eliminate contaminants are advised for marketing and extensive water/wastewater treatment.

Novel data on genotoxic assessment of bismuth sulfide nanoflowers in common carp Cyprinus carpio

The environmental impacts and risks of nanomaterials that are commonly used in different technologies are of great concern as their toxic effects on the aquatic ecosystem remain unclear. In this study, bismuth sulfide (Bi2S3) nanoflowers (nfs) were synthesized using a microwave-based hydrothermal process, and their genotoxic effects were investigated in the common carp, Cyprinus carpio. Bi2S3 nanoflowers were applied to common carp for 96 h. LC50 value (LC50 = 350 mg/L-1) was determined for acute toxicity with probit analysis, and three sublethal concentrations (35, 87, and 175 mg/L-1) were selected accordingly for genotoxicity tests. Such LC50 value - 350 mg L-1 for the common carp makes these nanoflowers non-toxic to aquatic organisms according to the EU-Directive 93/67/EEC classification scheme. Toxicological evaluations of the sublethal concentrations of Bi2S3 nanoflowers demonstrated that the 35 and 87 mg L-1 Bi2S3nfs groups were generally harmless and similar to the control group. Only the 175 mg L-1 Bi2S3nfs group had significant DNA damage frequency and nuclear abnormalities than the control and other Bi2S3nfs groups. To the best of our knowledge, this is a novel data on genotoxicity reported for fish species exposed to Bi2S3 nanoflowers; however, further systematic studies need to be performed to fully estimate the effects of Bi2S3 nanoflowers on aquatic life.

Integrated adsorption and photocatalytic degradation based removal of ciprofloxacin and sulfamethoxazole antibiotics using Fc@rGO-ZnO nanocomposite in aqueous systems

Ferrocene functionalized rGO-ZnO nanocomposite was synthesized via the facile hydrothermal method. ZnO was reduced over the 3-dimensional rGO framework (3D-Fc@rGO) using Camellia sinensis extract. The Fc@rGO-ZnO nanocomposite was employed for pharmaceutical degradation (sulfamethoxazole (SMX) and ciprofloxacin (CIP)) in an aqueous solution under UV C light. The physicochemical properties of the as-prepared photocatalyst were characterized using FTIR, XRD, FESEM, EDS mapping, HR-TEM, XPS, and DR-UV Vis. The as-synthesized Fc@rGO-ZnO photocatalyst performed remarkably against pristine ZnO, with a fivefold increase in removal efficiency. This superior activity was attributed to its improved light harvesting, charge carrier interface, and enhanced charge separation. Additionally, the photocatalyst obeyed the Lagergen model for pseudo-first-order kinetics. Congruously, the integrated approach of Fc@rGO and ZnO as oxidizing agents was proficient in removing >95% of antibiotics (CIP and SMX) within 180 min. Furthermore, the heterostructure configuration developed between Fc@rGO and ZnO helps in charge migration and generation of abundant •OH and •O₂^- radicals for photodegradation activities. The toxicity assessment of the treated solutions showed improved cell viability in the algal strains of Scenedesmus and Chlorella sp. Moreover, this novel approach for the synthesis of a photoactive nanocomposite is found to be low-cost and reusable for three cycles. The nanocomposite is environmentally sustainable paving the way for practical applications in the treatment of different classes of antibiotics.

Overview on recent advances of magnetic metal-organic framework (MMOF) composites in removal of heavy metals from aqueous system

Developing a novel, simple, and cost-effective analytical technique with high enrichment capacity and selectivity is crucial for environmental monitoring and remediation. Metal-organic frameworks (MOFs) are porous coordination polymers that are self-assembly synthesized from organic linkers and inorganic metal ions/metal clusters. Magnetic metal-organic framework (MMOF) composites are promising candidate among the new-generation sorbent materials available for magnetic solid-phase extraction (MSPE) of environmental contaminants due to their superparamagnetism properties, high crystallinity, permanent porosity, ultrahigh specific surface area, adaptable pore shape/sizes, tunable functionality, designable framework topology, rapid and ultrahigh adsorption capacity, and reusability. In this review, we focus on recent scientific progress in the removal of heavy metal ions present in contaminated aquatic system by using MMOF composites. Different types of MMOFs, their synthetic approaches, and various properties that are harnessed for removal of heavy metal ions from contaminated water are discussed briefly. Adsorption mechanisms involved, adsorption capacity, and regeneration of the MMOF sorbents as well as recovery of heavy metal ions adsorbed that are reported in the last ten years have been discussed in this review. Moreover, particular prospects, challenges, and opportunities in future development of MMOFs towards their greener synthetic approaches for their practical industrial applications have critically been considered in this review.

Exploring Microbial-Based Green Nanobiotechnology for Wastewater Remediation: A Sustainable Strategy

Water scarcity due to contamination of water resources with different inorganic and organic contaminants is one of the foremost global concerns. It is due to rapid industrialization, fast urbanization, and the low efficiency of traditional wastewater treatment strategies. Conventional water treatment strategies, including chemical precipitation, membrane filtration, coagulation, ion exchange, solvent extraction, adsorption, and photolysis, are based on adopting various nanomaterials (NMs) with a high surface area, including carbon NMs, polymers, metals-based, and metal oxides. However, significant bottlenecks are toxicity, cost, secondary contamination, size and space constraints, energy efficiency, prolonged time consumption, output efficiency, and scalability. On the contrary, green NMs fabricated using microorganisms emerge as cost-effective, eco-friendly, sustainable, safe, and efficient substitutes for these traditional strategies. This review summarizes the state-of-the-art microbial-assisted green NMs and strategies including microbial cells, magnetotactic bacteria (MTB), bio-augmentation and integrated bioreactors for removing an extensive range of water contaminants addressing the challenges associated with traditional strategies. Furthermore, a comparative analysis of the efficacies of microbe-assisted green NM-based water remediation strategy with the traditional practices in light of crucial factors like reusability, regeneration, removal efficiency, and adsorption capacity has been presented. The associated challenges, their alternate solutions, and the cutting-edge prospects of microbial-assisted green nanobiotechnology with the integration of advanced tools including internet-of-nano-things, cloud computing, and artificial intelligence have been discussed. This review opens a new window to assist future research dedicated to sustainable and green nanobiotechnology-based strategies for environmental remediation applications.

Emerging Trends in the Remediation of Persistent Organic Pollutants Using Nanomaterials and Related Processes: A Review

Persistent organic pollutants (POPs) have become a major global concern due to their large amount of utilization every year and their calcitrant nature. Due to their continuous utilization and calcitrant nature, it has led to several environmental hazards. The conventional approaches are expensive, less efficient, laborious, time-consuming, and expensive. Therefore, here in this review the authors suggest the shortcomings of conventional techniques by using nanoparticles and nanotechnology. Nanotechnology has shown immense potential for the remediation of such POPs within a short period of time with high efficiency. The present review highlights the use of nanoremediation technologies for the removal of POPs with a special focus on nanocatalysis, nanofiltration, and nanoadsorption processes. Nanoparticles such as clays, zinc oxide, iron oxide, aluminum oxide, and their composites have been used widely for the efficient remediation of POPs. Moreover, filtrations such as nanofiltration and ultrafiltration have also shown interest in the remediation of POPs from wastewater. From several pieces of literature, it has been found that nano-based techniques have shown complete removal of POPs from wastewater in comparison to conventional methods, but the cost is one of the major issues when it comes to nano- and ultrafiltration. Future research in nano-based techniques for POP remediation will solve the cost issue and will make it one of the most widely accepted and available techniques. Nano-based processes provide a sustainable solution to the problem of POPs.

A Weed-Derived Hierarchical Porous Carbon with a Large Specific Surface Area for Efficient Dye and Antibiotic Removal

Adsorption is an economical and efficient method for wastewater treatment, and its advantages are closely related to adsorbents. Herein, the Abutilon theophrasti medicus calyx (AC) was used as the precursor for producing the porous carbon adsorbent (PCAC). PCAC was prepared through carbonization and chemical activation. The product activated by potassium hydroxide exhibited a larger specific surface area, more mesopores, and a higher adsorption capacity than the product activated by sodium hydroxide. PCAC was used for adsorbing rhodamine B (RhB) and chloramphenicol (CAP) from water. Three adsorption kinetic models (the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models), four adsorption isotherm models (the Langmuir, Freundlich, Sips, and Redlich–Peterson models), and thermodynamic equations were used to investigate adsorption processes. The pseudo-second kinetic and Sips isotherm models fit the experimental data well. The adsorption mechanism and the reusability of PCAC were also investigated. PCAC exhibited a large specific surface area. The maximum adsorption capacities (1883.3 mg g⁻¹ for RhB and 1375.3 mg g⁻¹ for CAP) of PCAC are higher than most adsorbents. Additionally, in the fixed bed experiments, PCAC exhibited good performance for the removal of RhB. These results indicated that PCAC was an adsorbent with the advantages of low-cost, a large specific surface area, and high performance.