Advances and Applications of Water Phytoremediation: A Potential Biotechnological Approach for the Treatment of Heavy Metals from Contaminated Water

Modern-Day Green Strategies for the Removal of Chromium from Wastewater

Chromium is an essential element in various industrial processes, including stainless steel production, electroplating, metal finishing, leather tanning, photography, and textile manufacturing. However, it is also a well-documented contaminant of aquatic systems and agricultural land, posing significant economic and health challenges. The hexavalent form of chromium [Cr(VI)] is particularly toxic and carcinogenic, linked to severe health issues such as cancer, kidney disorders, liver failure, and environmental biomagnification. Due to the high risks associated with chromium contamination in potable water, researchers have focused on developing effective removal strategies. Among these strategies, biosorption has emerged as a promising, cost-effective, and energy-efficient method for eliminating toxic metals, especially chromium. This process utilizes agricultural waste, plants, algae, bacteria, fungi, and other biomass as adsorbents, demonstrating substantial potential for the remediation of heavy metals from contaminated environments at minimal cost. This review paper provides a comprehensive analysis of various strategies, materials, and mechanisms involved in the bioremediation of chromium, along with their commercial viability. It also highlights the advantages of biosorption over traditional chemical and physical methods, offering a thorough understanding of its applications and effectiveness.

Phytoremediation: Sustainable Approach for Heavy Metal Pollution

Rapid industrialization, mining, and other anthropogenic activities have poisoned our environment with heavy metals, negatively impacting all forms of life. Heavy metal pollution causes physiological and neurological disorders, as heavy metals are endocrine disrupters, carcinogenic, and teratogenic. Therefore, it becomes mandatory to address the challenge of heavy metal contamination on a global scale. Physical and chemical approaches have been employed for pollutant removal and detoxification, but these methods cannot be adopted universally due to high cost, labor intensiveness, and possible negative impact on natural microflora. Phytoremediation is one of the preferred and safest approaches for environmental management due to its high efficiency and low cost of investment. The plant can uptake the pollutants and heavy metals from water and soil through an intense root network via rhizofiltration and process via phytostabilization, phytovolatilization, and accumulation. At a cellular level, the phytoremediation process relies on natural mechanisms of plant cells, e.g., absorption, transpiration, intracellular storage, and accumulation to counter the detrimental effects of pollutants. It is widely accepted because of its novelty, low cost, and high efficiency; however, the process is comparatively slower. In addition, plants can store pollutants for a long time but again become a challenge at the end of the life cycle. The current review summarizes phytoremediation as a potential cure for heavy metal pollutants, released from natural as well as anthropogenic sources. It will provide insight into the advancement and evolution of advanced techniques like nanoremediation that can improve the rate of phytoremediation, along with making it sustainable, cost-effective, and economically viable.

Phytoremediation of metals in oil sands process affected water by native wetland species

Process affected water and other industrial wastewaters are a major environmental concern. During oil sands mining, large amounts of oil sands process affected water (OSPW) are generated and stored in ponds until reclaimed and ready for surface water discharge. While much research has focused on organics in process waters, trace metals at high concentrations may also pose environmental risks. Phytoremediation is a cost effective and sustainable approach that employs plants to extract and reduce contaminants in water. The research was undertaken in mesocosm scale constructed wetlands with plants exposed to OSPW for 60 days. The objective was to screen seven native emergent wetland species for their ability to tolerate high metal concentrations (arsenic, cadmium, copper, chromium, copper, nickel, selenium, zinc), and then to evaluate the best performing species for OSPW phytoremediation. All native plant species, except Glyceria grandis, tolerated and grew in OSPW. Carex aquatilis (water sedge), Juncus balticus (baltic rush), and Typha latifolia (cattail) had highest survival and growth, and had high metal removal efficiencies for arsenic (81-87 %), chromium (78-86 %), and cadmium (74-84 %), relative to other metals; and greater than 91 % of the dissolved portions were removed. The native plant species were efficient accumulators of all metals, as demonstrated by high root and shoot bioaccumulation factors; root accumulation was greater than shoot accumulation. Translocation factor values were greater than one for Juncus balticus (chromium, zinc) and Carex aquatilis (cadmium, chromium, cobalt, nickel). The results demonstrate the potential suitability of these species for phytoremediation of a number of metals of concern and could provide an effective and environmentally sound remediation approach for wastewaters.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

Biodiversity and human health: A scoping review and examples of underrepresented linkages

Mounting evidence supports the connections between exposure to environmental typologies(such as green and blue spaces)and human health. However, the mechanistic links that connect biodiversity (the variety of life) and human health, and the extent of supporting evidence remain less clear. Here, we undertook a scoping review to map the links between biodiversity and human health and summarise the levels of associated evidence using an established weight of evidence framework. Distinct from other reviews, we provide additional context regarding the environment-microbiome-health axis, evaluate the environmental buffering pathway (e.g., biodiversity impacts on air pollution), and provide examples of three under- or minimally-represented linkages. The examples are (1) biodiversity and Indigenous Peoples' health, (2) biodiversity and urban social equity, and (3) biodiversity and COVID-19. We observed a moderate level of evidence to support the environmental microbiota-human health pathway and a moderate-high level of evidence to support broader nature pathways (e.g., greenspace) to various health outcomes, from stress reduction to enhanced wellbeing and improved social cohesion. However, studies of broader nature pathways did not typically include specific biodiversity metrics, indicating clear research gaps. Further research is required to understand the connections and causative pathways between biodiversity (e.g., using metrics such as taxonomy, diversity/richness, structure, and function) and health outcomes. There are well-established frameworks to assess the effects of broad classifications of nature on human health. These can assist future research in linking biodiversity metrics to human health outcomes. Our examples of underrepresented linkages highlight the roles of biodiversity and its loss on urban lived experiences, infectious diseases, and Indigenous Peoples' sovereignty and livelihoods. More research and awareness of these socioecological interconnections are needed.

Application of phytoaccumulation perspective of Monochoria hastate L. on fluoride contaminated water in hydroponic treatment: its statistical design and characterization studies

The present research work approaches the accumulation of fluoride ions from contaminated water using an aquatic plant Monochoria hastate L. in hydroponic culture. A design of experiment (DOE) has been adopted and an analysis of variance has been conducted to establish the statistical significance of various process parameters. The different experimental factors are root and shoot (Factor A), fluoride concentration (Factor B), and experimental days (Factor C) largely influence the output response. Plants treated with 5 mg/L of fluoride solutions accumulated the highest concentration in root biomass 1.23 mg/gm, and shoot biomass 0.820 mg/gm, dry weight after 21 days' experimentation. The accumulation mechanism and potentiality of treated plants depend on root cells of the plasma membrane and energy-capturing molecules of adenosine triphosphate. Monochoria hastate L. root biomass was characterized to confirm the accumulation of fluoride ions in the experimented plants using scanning electron micrographs-energy dispersive spectrum (SEM-EDS), and Fourier transforms infrared analysis (FTIR) analysis.

Valorization of Fibrous Plant-Based Food Waste as Biosorbents for Remediation of Heavy Metals from Wastewater-A Review

Mobilization of heavy metals in the environment has been a matter of concern for several decades due to their toxicity for humans, environments, and other living organisms. In recent years, use of inexpensive and abundantly available biosorbents generated from fibrous plant-based food-waste materials to remove heavy metals has garnered considerable research attention. The aim of this review is to investigate the applicability of using fibrous plant-based food waste, which comprises different components such as pectin, hemicellulose, cellulose, and lignin, to remove heavy metals from wastewater. This contribution confirms that plant-fiber-based food waste has the potential to bind heavy metals from wastewater and aqueous solutions. The binding capacities of these biosorbents vary depending on the source, chemical structure, type of metal, modification technology applied, and process conditions used to improve functionalities. This review concludes with a discussion of arguments and prospects, as well as future research directions, to support valorization of fibrous plant-based food waste as an efficient and promising strategy for water purification.

The Impact of Heavy Metal Accumulation on Some Physiological Parameters in Silphium perfoliatum L. Plants Grown in Hydroponic Systems

Heavy metals like cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), resulting from anthropogenic activities, are elements with high persistence in nature, being able to accumulate in soils, water, and plants with significant impact to human and animal health. This study investigates the phytoremediation capacity of Silphium perfoliatum L. as a specific heavy metal hyperaccumulator and the effects of Cu, Zn, Cd, and Pb on some physiological and biochemical indices by growing plants under floating hydroponic systems in nutrient solutions under the presence of heavy metals. One-year-old plants of S. perfoliatum grown for 20 days in Hoagland solution with the addition of (ppm) Cu-400, Zn-1200, Cd-20, Pb-400, and Cu+Zn+Cd+Pb (400/1200/20/400) were investigated with respect to the control. The level of phytoremediation, manifested by the ability of heavy metal absorption and accumulation, was assessed. In addition, the impact of stress on the proline content, photosynthetic pigments, and enzymatic activity, as being key components of metabolism, was determined. The obtained results revealed a good absorption and selective accumulation capacity of S. perfoliatum plants for the studied heavy metals. Therefore, Cu and Zn mainly accumulate in the stems, Cd in the roots and stems, while Pb mainly accumulates in the roots. The proline tended to increase under stress conditions, depending on the pollutant and its concentration, with higher values in leaves and stems under the associated stress of the four metals and individually for Pb and Cd. In addition, the enzymatic activity recorded different values depending on the plant organ, its type, and the metal concentration on its substrate. The obtained results indicate a strong correlation between the metal type, concentration, and the mechanisms of absorption/accumulation of S. perfoliatum species, as well as the specific reactions of metabolic response.

Phytoremediation of Potentially Toxic Elements: Role, Status and Concerns

Environmental contamination with a myriad of potentially toxic elements (PTEs) is triggered by various natural and anthropogenic activities. However, the industrial revolution has increased the intensity of these hazardous elements and their concentration in the environment, which, in turn, could provoke potential ecological risks. Additionally, most PTEs pose a considerable nuisance to human beings and affect soil, aquatic organisms, and even nematodes and microbes. This comprehensive review aims to: (i) introduce potentially toxic elements; (ii) overview the major sources of PTEs in the major environmental compartments; (iii) briefly highlight the major impacts of PTEs on humans, plants, aquatic life, and the health of soil; (iv) appraise the major methods for tackling PTE-caused pollution; (v) discuss the concept and applications of the major eco-technological/green approaches (comprising phytoextraction, rhizofiltration, phytostabilization, phytovolatilization, and phytorestoration); (vi) highlight the role of microbes in phytoremediation under PTE stress; and (vii) enlighten the major role of genetic engineering in advancing the phytoremediation of varied PTEs. Overall, appropriate strategies must be developed in order to stop gene flow into wild species, and biosafety issues must be properly addressed. Additionally, consistent efforts should be undertaken to tackle the major issues (e.g., risk estimation, understanding, acceptance and feasibility) in order to guarantee the successful implementation of phytoremediation programs, raise awareness of this green technology among laymen, and to strengthen networking among scientists, stakeholders, industrialists, governments and non-government organizations.

Synthesis of Metalorganic Copolymers Containing Various Contorted Units and Iron(II) Clathrochelates with Lateral Butyl Chains: Conspicuous Adsorbents of Lithium Ions and Methylene Blue

We report the synthesis of three highly soluble metalorganic copolymers, TCP1-3, that were made from a one-pot complexation of iron(II) clathrochelate units that are interconnected by various thioether-containing contorted groups. TCP1-3 were converted into their poly(vinyl sulfone) derivatives OTCP1-3 quantitatively via the selective oxidation of the thioether moieties into their respective sulfones. All of the copolymers, TCP1-3 and OTCP1-3, underwent structural analysis by various techniques; namely, ¹H- and ¹³C-nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC). The copolymers were tested as potent lithium ions adsorbents revealing a maximum adsorption (q_m) value of 2.31 mg g^-1 for OTCP2. Furthermore, this same copolymer was found to be a promising adsorbent of methylene blue (MEB); an isothermal adsorption study divulged that OTCP2's uptake of MEB from an aqueous solution (following the Langmuir model) was, at maximum adsorption capacity, (q_m) of 480.77 mg g^-1; whereas the kinetic study divulged that the adsorption follows pseudo second-order kinetics with an equilibrium adsorption capacity (q_e,cal) of 45.40 mg g^-1.

Advances in biological methods for the sequestration of heavy metals from water bodies: A review

Pollution is a major concern of the modern era as it affects all the principal aspects of the environment, especially the hydrosphere. Pollution with heavy metals has unequivocally threatened aquatic bodies and organisms as these metals are persistent, non-biodegradable, and toxic. Heavy metals tend to accumulate in the environment and eventually in humans, which makes their efficient removal a topic of paramount importance. Treatment of metal-contaminated water can be done both via chemical and biological methods. Where remediation through conventional methods is expensive and generates a large amount of sludge, biological methods are favoured over older and prevalent chemical purification processes because they are cheaper and environment friendly. The present review attempts to summarise effective methods for the remediation of water contaminated with heavy metals. We concluded that in biological techniques, bio-sorption is among the most employed and successful mechanisms because of its high efficacy and eco-friendly nature.

Novel strategies and advancement in reducing heavy metals from the contaminated environment

The most contemporary ecological issues are the dumping of unprocessed factories' effluent. As a result, there is an increasing demand for creative, practical, environmentally acceptable, and inexpensive methodologies to remediate inorganic metals (Hg, Cr, Pb, and Cd) liquidated into the atmosphere, protecting ecosystems. Latest innovations in biological metals have driven natural treatment as a viable substitute for traditional approaches in this area. To eliminate pesticide remains from soil/water sites, technologies such as oxidation, burning, adsorption, and microbial degradation have been established. Bioremediation is a more cost-effective and ecologically responsible means of removing heavy metals than conventional alternatives. As a result, microorganisms have emerged as a necessary component of methyl breakdown and detoxification via metabolic reactions and hereditary characteristics. The utmost operative variant for confiscating substantial metals commencing contaminated soil was A. niger, which had a maximum bioaccumulation efficiency of 98% (Cd) and 43% (Cr). Biosensor bacteria are both environmentally sustainable and cost-effective. As a result, microbes have a range of metal absorption processes that allow them to have higher metal biosorption capabilities. Additionally, the biosorption potential of bacterium, fungus, biofilm, and algae, inherently handled microorganisms that immobilized microbial cells for the elimination of heavy metals, was reviewed in this study. Furthermore, we discuss some of the challenges and opportunities associated with producing effective heavy metal removal techniques, such as those that employ different types of nanoparticles.

Phytoremediation of Heavy Metals: An Indispensable Contrivance in Green Remediation Technology

Environmental contamination is triggered by various anthropogenic activities, such as using pesticides, toxic chemicals, industrial effluents, and metals. Pollution not only affects both lotic and lentic environments but also terrestrial habitats, substantially endangering plants, animals, and human wellbeing. The traditional techniques used to eradicate the pollutants from soil and water are considered expensive, environmentally harmful and, typically, inefficacious. Thus, to abate the detrimental consequences of heavy metals, phytoremediation is one of the sustainable options for pollution remediation. The process involved is simple, effective, and economically efficient with large-scale extensive applicability. This green technology and its byproducts have several other essential utilities. Phytoremediation, in principle, utilizes solar energy and has an extraordinary perspective for abating and assembling heavy metals. The technique of phytoremediation has developed in contemporary times as an efficient method and its success depends on plant species selection. Here in this synthesis, we are presenting a scoping review of phytoremediation, its basic principles, techniques, and potential anticipated prospects. Furthermore, a detailed overview pertaining to biochemical aspects, progression of genetic engineering, and the exertion of macrophytes in phytoremediation has been provided. Such a promising technique is economically effective as well as eco-friendly, decontaminating and remediating the pollutants from the biosphere.

In-situ, Ex-situ, and nano-remediation strategies to treat polluted soil, water, and air - A review

Nanotechnology, as an emerging science, has taken over all fields of life including industries, health and medicine, environmental issues, agriculture, biotechnology etc. The use of nanostructure molecules has revolutionized all sectors. Environmental pollution is a great concern now a days, in all industrial and developing as well as some developed countries. A number of remedies are in practice to overcome this problem. The application of nanotechnology in the bioremediation of environmental pollutants is a step towards revolution. The use of various types of nanoparticles (TiO₂ based NPs, dendrimers, Fe based NPs, Silica and carbon nanomaterials, Graphene based NPs, nanotubes, polymers, micelles, nanomembranes etc.) is in practice to diminish environmental hazards. For this many In-situ (bioventing, bioslurping, biosparging, phytoremediation, permeable reactive barrier etc.) and Ex-situ (biopile, windrows, bioreactors, land farming etc.) methodologies are employed. Improved properties like nanoscale size, less time utilization, high adaptability for In-situ and Ex-situ use, undeniable degree of surface-region to-volume proportion for possible reactivity, and protection from ecological elements make nanoparticles ideal for natural applications. There are distinctive nanomaterials and nanotools accessible to treat the pollutants. Each of these methods and nanotools depends on the properties of foreign substances and the pollution site. The current designed review highlights the techniques used for bioremediation of environmental pollutants as well as use of various nanoparticles along with proposed In-situ and Ex-situ bioremediation techniques.

Expression of Cytochrome c3 from Desulfovibrio vulgaris in Plant Leaves Enhances Uranium Uptake and Tolerance of Tobacco

Cytochrome c3 (uranyl reductase) from Desulfovibrio vulgaris can reduce uranium in bacterial cells and in cell-free systems. This gene was introduced in tobacco under control of the RbcS promoter, and the resulting transgenic plants accumulated uranium when grown on a uranyl ion containing medium. The uptaken uranium was detected by EM in chloroplasts. In the presence of uranyl ions in sublethal concentration, the transgenic plants grew phenotypically normal while the control plants' development was impaired. The data on uranium oxidation state in the transgenic plants and the possible uses of uranium hyperaccumulation by plants for environmental cleanup are discussed.