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"Wastewater purification"
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Flatband λ-Ti3O5 towards extraordinary solar steam generation
Solar steam interfacial evaporation represents a promising strategy for seawater desalination and wastewater purification owing to its environmentally friendly character
1
–
3
. To improve the solar-to-steam generation, most previous efforts have focused on effectively harvesting solar energy over the full solar spectrum
4
–
7
. However, the importance of tuning joint densities of states in enhancing solar absorption of photothermal materials is less emphasized. Here we propose a route to greatly elevate joint densities of states by introducing a flat-band electronic structure. Our study reveals that metallic λ-Ti
3
O
5
powders show a high solar absorptivity of 96.4% due to Ti–Ti dimer-induced flat bands around the Fermi level. By incorporating them into three-dimensional porous hydrogel-based evaporators with a conical cavity, an unprecedentedly high evaporation rate of roughly 6.09 kilograms per square metre per hour is achieved for 3.5 weight percent saline water under 1 sun of irradiation without salt precipitation. Fundamentally, the Ti–Ti dimers and U-shaped groove structure exposed on the λ-Ti
3
O
5
surface facilitate the dissociation of adsorbed water molecules and benefit the interfacial water evaporation in the form of small clusters. The present work highlights the crucial roles of Ti–Ti dimer-induced flat bands in enchaining solar absorption and peculiar U-shaped grooves in promoting water dissociation, offering insights into access to cost-effective solar-to-steam generation.
A route to greatly elevate joint densities of states by introducing a flat-band electronic structure is demonstrated, showing metallic λ-Ti
3
O
5
powders have a high solar absorptivity and offering insights into access to cost-effective solar-to-steam generation.
Journal Article
Self-cycled photo-Fenton-like system based on an artificial leaf with a solar-to-H2O2 conversion efficiency of 1.46
Millions of families around the world remain vulnerable to water scarcity and have no access to drinking water. Advanced oxidation processes (AOPs) are an effective way towards water purification with qualified reactive oxygen species (ROSs) while are impeded by the high-cost and tedious process in either input of consumable reagent, production of ROSs, and the pre-treatment of supporting electrolyte. Herein, we couple solar light-assisted H
2
O
2
production from water and photo-Fenton-like reactions into a self-cyclable system by using an artificial leaf, achieving an unassisted H
2
O
2
production rate of 0.77 μmol/(min·cm
2
) under 1 Sun AM 1.5 illumination. Furthermore, a large (70 cm
2
) artificial leaf was used for an unassisted solar-driven bicarbonate-activated hydrogen peroxide (BAP) system with recycled catalysts for real-time wastewater purification with requirements for only water, oxygen and sunlight. This demonstration highlights the feasibility and scalability of photoelectrochemical technology for decentralized environmental governance applications from laboratory benchtops to industry.
Continuous generation of reactive oxygen species is desirable in the advanced oxidation process. Here, the authors report a self-cycled photoFenton-like with a scalable artificial leaf for production of H
2
O
2
from water with solar-to-H
2
O
2
efficiency of 1.46%.
Journal Article
A review on degradation of organic dyes by using metal oxide semiconductors
The discharge of organic dye pollutants in natural water bodies has put forward a big challenge of providing clean water to a large part of the population. As the population is increasing with time, only underground water is not sufficient to complete the water requirements of everyone everywhere. Purification of wastewater and its reuse is the only way to fulfill the water needs. Nanotechnology has been used very efficiently for wastewater treatment via photocatalytic degradation of dye molecules. In the past few years, a lot of investigations have been done to enhance the photocatalytic activity of metal oxide semiconductors for water purification. In this review, we have discussed the different methods of synthesis of various metal oxide semiconductor nanoparticles, energy band gap, their role as efficient photocatalysts, radiations used for photocatalytic reactions, and their degradation efficiency to degrade the dye pollutants. We have also discussed the nanocomposites of metal oxide with graphene. These nanocomposites have been utilized as the efficient photocatalyst due to unique characteristics of graphene such as extended range of light absorption, separation of charges, and high capacity of adsorption of the dye pollutants.
Journal Article
Sustainable microalgal biomass production in food industry wastewater for low-cost biorefinery products: a review
Microalgae are recognized as cell factories enriched with biochemicals suitable as feedstock for bio-energy, food, feed, pharmaceuticals, and nutraceuticals applications. The industrial application of microalgae is challenging due to hurdles associated with mass cultivation and biomass recovery. The scale-up production of microalgal biomass in freshwater is not a sustainable solution due to the projected increase of freshwater demands in the coming years. Microalgae cultivation in wastewater is encouraged in recent years for sustainable bioeconomy from biorefinery processes. Wastewater from the food industry is a less-toxic growth medium for microalgal biomass production. Traditional wastewater treatment and management processes are expensive; hence it is highly relevant to use low-cost wastewater treatment processes with revenue generation through different products. Microalgae are accepted as potential biocatalysts for the bioremediation of wastewater. Microalgae based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. This review highlights the importance of microalgal biomass production in food processing wastewater, their characteristics, and different microalgal cultivation methods, followed by nutrient absorption mechanisms. Towards the end of the review, different microalgae biomass harvesting processes with biorefinery products, and void gaps that tend to hinder the biomass production with future perspectives will be intended. Thus, the review could claim to be valuable for sustainable microalgae biomass production for eco-friendly bioproduct conversions.
Graphical abstract
Journal Article
Unlocking single-atom induced electronic metal-support interactions in electrocatalytic one-electron water oxidation for wastewater purification
Electro-oxidation is a promising green technology for decentralized wastewater purification. However, its efficacy is primarily constrained by the selectivity and efficiency of hydroxyl radical (•OH) generation through one-electron water oxidation. In this study, we elucidate the mechanism of electronic metal-support interactions (EMSI) of Ni single-atoms on antimony-doped tin oxide anode (Ni/ATO) to enhance •OH production and overall water treatment efficiency. We experimentally and theoretically investigate both the structural evolution process and micro-interface mechanisms associated with the EMSI effects induced by Ni single-atoms. The optimized electronic structures in the interfacial catalysts under EMSI conditions and the co-catalytic role of Ni single-atoms synergistically facilitate selective and efficient •OH generation, resulting in over a fivefold increase in its steady-state concentration and tenfold enhancement in pseudo-first-order rate constant of sulfamethoxazole degradation compared to those on bare ATO. With the EMSI, rapid electron transfer channels were established for a marked enhancement in the adsorption, conversion, and dissociation of interfacial H
2
O molecules. Notably, it is revealed that Ni single-atoms serve as co-catalytic sites, exhibiting a “H-pulling effect” that is crucial for •OH generation. The Ni/ATO anode demonstrates great efficiency in degrading various refractory organic pollutants, and effectively treats real pharmaceutical wastewater with low energy consumption. Furthermore, it presents remarkable stability and adaptability, while maintaining a minimal environmental footprint during wastewater treatment processes. This work addresses the theoretical gaps between EMSI effects and co-catalysis in electro-oxidation systems, while providing a robust technological solution for wastewater purification.
The study reveals that electronic metal-support interactions in Ni/antimony-doped tin oxide boost selective •OH production. Ni single-atoms, acting as co-catalysts via a “H-pulling effect”, significantly enhance pollutant degradation efficiency.
Journal Article
A review on sources of heavy metals, their toxicity and removal technique using physico-chemical processes from wastewater
The world is facing environmental pollution and is in an alarming situation due to industrialization and urbanization. Especially, industrial wastewater discharge is causing serious pollution in the environment (water, soil, and air) and has become a challenge for researchers and scientists. Wastewater contains heavy metals like Cu, Ni, Cr, Pb, and Ar and causes toxicity in living beings and the environment. In this review, the sources of heavy metals and their toxicological effects on the environment have been reviewed. Various remediation techniques such as reverse osmosis, chemical precipitation, and ultrafiltration are being used for the treatment of wastewater, but still are limited in their efficiencies, residues, cost, and versatility. In this study, the most promising wastewater treatment technique, the physic-chemical technique, has been reviewed along with its working mechanism and efficiency. Further, the pros and cons of this technique and sub-techniques have also been reviewed to provide a basic understanding to beginners and a pathway to experts in the selection of better techniques.
Journal Article
Vertically aligned reduced graphene oxide/Ti3C2Tx MXene hybrid hydrogel for highly efficient solar steam generation
Effective utilization of abundant solar energy for desalination of seawater and purification of wastewater is one of sustainable techniques for production of clean water, helping relieve global water resource shortage. Herein, we fabricate a vertically aligned reduced graphene oxide/Ti
3
C
2
T
x
MXene (A-RGO/MX) hybrid hydrogel with aligned channels as an independent solar steam generation device for highly efficient solar steam generation. The vertically aligned channels, generated by a liquid nitrogen-assisted directional-freezing process, not only rapidly transport water upward to the evaporation surface for efficient solar steam generation, but also facilitate multiple reflections of solar light inside the channels for efficient solar light absorption. The deliberate slight reduction endows the RGO with plenty of polar groups, decreasing the water vaporization enthalpy effectively and hence accelerating water evaporation efficiently. The MXene sheets, infiltrated inside the A-RGO hydrogel on the basis of Marangoni effect, enhance light absorption capacity and photothermal conversion performance. As a result, the A-RGO/MX hybrid hydrogel achieves a water evaporation rate of 2.09 kg·m
−2
·h
−1
with a high conversion efficiency of 93.5% under 1-sun irradiation. Additionally, this photothermal conversion hydrogel rapidly desalinates seawater and purifies wastewater to generate clean water with outstanding ion rejection rates of above 99% for most ions.
Journal Article
Recent Advances in Various Starch Formulation for Wastewater Purification via Adsorption Technique: A Review
Water purification is considered one of the most essential issues in our lives. Therefore, the contamination of water surfaces owing to the hasty upsurge in industrialization has received great global attention because of its potential danger to human health and the eco-system. Particularly, the discharge of various non-biodegradable contaminants into the water body—heavy metal ions, organic dyes, pharmaceutical antibiotics, pesticides, and oils—causes these contaminants to accumulate on the water's surface and have harmful impacts on humans and the environment. Several conventional methods can be applied to solve this problem, including chemical oxidation, precipitation, coagulation, and so on. However, they suffer from serious limitations: high cost, limited functionality, prolonged and heavy energy use, and poor separation efficiency. Conversely, the adsorption technique has recently attracted a lot of attention for wastewater treatment thanks to its remarkable benefits of being a simple, highly selective, and low-cost technique. Recently, natural polysaccharides (especially starch)-based adsorbents have received great interest in water purification owing to their outstanding properties, including being easily available, non-toxic, low-cost, biodegradable, and biocompatible. However, it possesses notable drawbacks that prevent it from being used alone as an adsorbent for wastewater treatment, including low thermal stability, slight water solubility, and rapid degradability in water. Therefore, this review highlights a comprehensive presentation about various starch modifications: starch-based grafts, hydrogels, aerogels, beads, nanofibers, and nanocomposite formulations to remove several toxic contaminants, including toxic heavy metal ions, organic dyes, pharmaceutical antibiotics, pesticides, and oils.
Journal Article
The Toxic Truth About Carbon Nanotubes in Water Purification: a Perspective View
Without nanosafety guidelines, the long-term sustainability of carbon nanotubes (CNTs) for water purifications is questionable. Current risk measurements of CNTs are overshadowed by uncertainties. New risks associated with CNTs are evolving through different waste water purification routes, and there are knowledge gaps in the risk assessment of CNTs based on their physical properties. Although scientific efforts to design risk estimates are evolving, there remains a paucity of knowledge on the unknown health risks of CNTs. The absence of universal CNT safety guidelines is a specific hindrance. In this paper, we close these gaps and suggested several new risk analysis roots and framework extrapolations from CNT-based water purification technologies. We propose a CNT safety clock that will help assess risk appraisal and management. We suggest that this could form the basis of an acceptable CNT safety guideline. We pay particular emphasis on measuring risks based on CNT physico-chemical properties such as diameter, length, aspect ratio, type, charge, hydrophobicity, functionalities and so on which determine CNT behaviour in waste water treatment plants and subsequent release into the environment.
Journal Article