Novel biofiltration methods for the treatment of heavy metals from industrial wastewater

Efficient treatment of secondary treated refinery wastewater using sand biofiltration: Removal of hazardous organic pollutants

This study explored the potential of sand biofiltration for tertiary treatment of real refinery wastewater. The biofilter (2 cm (I.D.) x 15 cm (L)) operated on secondary treated refinery wastewater at flow rate of 1 mL/min had empty bed contact time (EBCT) of 47.12 min for one circulation. Maximum reduction in COD after 4, 8 and 12 times recirculation was 25 %, 52 % and 56 %; while the TOC reduction was 33 %, 43 % and 51 %, respectively, after biofilm development over 30 days. Quantification using two dimensional gas chromatography - time of flight mass spectrometry (GCxGC-TOF MS) revealed that several of the identified target compounds could not be detected in the wastewater after 12 recirculations. After 8 times recirculation, most of the compounds showed very high removal efficiency. For biofiltration over the flow rate range 2-10 mL/min, the reduction in COD and NH4+-N ranged from 62-73 % and 78-86 %, respectively, after 8 times recirculation. The nitrite concentration first increased and subsequently decreased, while the nitrate concentration continuously increased with increase in the number of recirculations. Solid phase micro-extraction (SPME) analysis of the aqueous phase using GCxGC-TOF MS and a semi-quantitative approach indicated that the removal of predominant classes of compounds was greater than 95 % after 8 times recirculation, with maximum reduction occurring in the first pass through the biofilter. Assimilable organic carbon (AOC) reduction was 98 % after 8 times recirculation. Metagenomic analysis revealed that Proteobacteria was the most dominant phylum in the biofilter. Many known polynuclear aromatic hydrocarbon (PAH) degraders, such as Sphingomonadales, Burkholderiales, Rhodobacterales and Rhodospirillales, were found in the biofilter leading to high removal efficiency of hazardous organic pollutants.

Animal waste as a valuable biosorbent in the removal of heavy metals from aquatic ecosystem-an eco-friendly approach

Toxic pollutants in the form of heavy metals are added through various anthropogenic activities daily into the aquatic ecosystem beyond their permissible limits, and their bioaccumulation capacity makes them hazardous substances for the survival of all organisms. Thus, their removal from aquatic ecosystems is the need of the hour. Treatment of wastewater containing heavy metals through biosorption is gaining popularity and is being explored all around the world due to its various advantages over conventional methods of treatment. Utilization of animal waste as a biomaterial could be the best solution to remove it from the ecosystem. Such treatment methods are a blessing for developing and underdeveloped countries due to their low cost. This paper provides in-depth details about heavy metals, their health implications, mechanisms of toxicity, modes of transportation, and conventional treatment approaches. A comprehensive understanding of the biosorption process, encompassing its world scenario, evolution, mechanisms, factors affecting the process, and advantages, will also be covered. Finally, animal wastes and their applicability in the removal of heavy metal pollutants from wastewater shall also be thoroughly reviewed, followed by their future utility and recommendations.

Zeolite and Neurodegenerative Diseases

Neurodegenerative diseases (NDs), characterized by progressive degeneration and death of neurons, are strongly related to aging, and the number of people with NDs will continue to rise. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common NDs, and the current treatments offer no cure. A growing body of research shows that AD and especially PD are intricately related to intestinal health and the gut microbiome and that both diseases can spread retrogradely from the gut to the brain. Zeolites are a large family of minerals built by [SiO4]4- and [AlO4]5- tetrahedrons joined by shared oxygen atoms and forming a three-dimensional microporous structure holding water molecules and ions. The most widespread and used zeolite is clinoptilolite, and additionally, mechanically activated clinoptilolites offer further improved beneficial effects. The current review describes and discusses the numerous positive effects of clinoptilolite and its forms on gut health and the gut microbiome, as well as their detoxifying, antioxidative, immunostimulatory, and anti-inflammatory effects, relevant to the treatment of NDs and especially AD and PD. The direct effects of clinoptilolite and its activated forms on AD pathology in vitro and in vivo are also reviewed, as well as the use of zeolites as biosensors and delivery systems related to PD.

Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing

Silver ions (Ag+) are crucial in various fields, but pose environmental and health risks at high concentrations. This study presents a straightforward approach for the ultra-trace detection of Ag+, utilizing a composite of a cytosine-rich oligonucleotide (CRO) and an electrochemically reduced graphene oxide (ERGO). Initially, ERGO was synthesized on a glassy carbon electrode (GCE) through the reduction of graphene oxide (GO) via cyclic voltammetry. A methylene blue-tagged CRO (MB-CRO) was then anchored to the ERGO surface through π-π interactions, resulting in the formation of an MB-CRO-modified ERGO electrode (MB-CRO/ERGO-GCE). The interaction with Ag+ ions induced the formation of silver-mediated C-Ag+-C coordination, prompting the MB-CRO to adopt a hairpin structure. This conformational change led to the desorption of the MB-CRO from the ERGO-GCE, causing a variation in the redox current of the methylene blue associated with the MB-CRO. Electrochemical assays revealed that the sensor exhibits extraordinary sensitivity to Ag+ ions, with a linear detection range from 1 femtomolar (fM) to 100 nanomolars (nM) and a detection limit of 0.83 fM. Moreover, the sensor demonstrated high selectivity for Ag+ ions and several other benefits, including stability, reproducibility, and straightforward fabrication and operational procedures. Additionally, real sample analyses were performed using the modified electrode to detect Ag+ in tap and pond water samples, yielding satisfactory recovery rates.

Green Organo-Photooxidative Method for the Degradation of Methylene Blue Dye

This study used an organophoto-oxidative material to degrade the toxic azo dye, methylene blue (MB), due to its hazardous effects on aquatic life and humans. MB is traditionally degraded using metal-based catalysts, resulting in high costs. Several organic acids were screened for organo-photooxidative applications against various azo dyes, and ascorbic acid (AA), also known as vitamin C, was found to be best for degradation due to its high photooxidative activity. It is an eco-friendly, edible, and efficient photooxidative material. A photocatalytic box has been developed for the study of organo-photooxidative activity. It was found that when AA was added, degradation efficiency increased from 42 to 95% within 240 min. Different characterization techniques, such as HPLC and GC-MS, were used after degradation for the structural elucidation of degraded products. DFT study was done for the investigation of the mechanistic study behind the degradation process. A statistical tool, RSM, was used for the optimization of parameters (concentration of dye, catalyst, and time). This study develops sustainable and effective solutions for wastewater treatment.

Novel eco-friendly polylactic acid nanocomposite integrated membrane system for sustainable wastewater treatment: Performance evaluation and antifouling analysis

Water contamination caused by heavy metals, nutrients, and organic pollutants of varying particle sizes originating from domestic and industrial processes poses a significant global challenge. There is a growing concern, particularly regarding the presence of heavy metals in freshwater sources, as they can be toxic even at low concentrations, posing risks to human health and the environment. Currently, membrane technologies are recognized as effective and practical for treating domestic and industrial wastewater. However, these technologies are hindered by fouling issues. Furthermore, the utilization of conventional membranes leads to the accumulation of non-recyclable synthetic polymers, commonly used in their production, resulting in adverse environmental consequences. In light of our previously published studies on environmentally friendly, biodegradable polylactic acid (PLA) nanocomposite mixed matrix membranes (MMMs), we selected two top-performing PLA-based ultrafiltration nanocomposite membranes: one negatively charged (PLA-M-) and one positively charged (PLA-M+). We integrated these membranes into systems with varying arrangements to control fouling and eliminate heavy metals, organic pollutants, and nutrients from raw municipal wastewater collected by the local wastewater treatment plant in Abu Dhabi (UAE). The performance of two integrated systems (i.e., PLA-M+/PLA-M- and PLA-M-/PLA-M+) was compared in terms of permeate flux, contaminant removal efficiencies, and fouling mitigation. The PLA-M+/PLA-M- system achieved removal efficiencies of 79.6 %, 92.6 %, 88.7 %, 85.2 %, 98.9 %, 94 %, 83.3 %, and 98.3 % for chemical oxygen demand (COD), nitrate (NO3--N), phosphate (PO43--P), ammonium (NH4+-N), iron (Fe), zinc (Zn), nickel (Ni), and copper (Cu), respectively. On the other hand, the PLA-M-/PLA-M+ system recorded removal efficiencies of 85.8 %, 95.9 %, 100 %, 81.9 %, 99.3 %, 91.9 %, 72.9 %, and 98.9 % for COD, NO3--N, PO43--P, NH4+-N, Fe, Zn, Ni, and Cu, respectively. Notably, the PLA-M-/PLA-M+ system demonstrated superior antifouling resistance, making it the preferred integrated system. These findings demonstrate the potential of eco-friendly PLA nanocomposite UF-MMMs as a promising alternative to petroleum-based polymeric membranes for efficient and sustainable wastewater treatment.

Bioremediation of hazardous heavy metals by marine microorganisms: a recent review

Heavy metals (HMs) like Zn, Cu, Pb, Ni, Cd, and Hg, among others, play a role in several environmental problems. The marine environment is polluted by several contaminants, such as HMs. A variety of physico-chemical methods usually available for sanitation HMs remediation suffer from either limitation. Bioremediation is a promising way of dealing with HMs pollution. Microbes have the ability with various potencies to resist HMs tension. The current review discusses the main sources and influences of HMs, the role of marine microorganisms in HMs bioremediation, as well as the microbial mechanisms for HMs detoxification and transformation. This review paper aims to provide an overview of the bioremediation technologies that are currently available for the removal of HMs ions from industrial and urban effluent by aquatic organisms such as bacteria, fungi, and microalgae, particularly those that are isolated from marine areas. The primary goals are to outline various studies and offer helpful information about the most important aspects of the bioelimination techniques. The biotreatment practices have been primarily divided into three techniques based on this topic. They are biosorption, bioaccumulation, bioleaching, and biotransformation. This article gives the brief view on the research studies about bioremediation of HMs using marine microorganisms. The current review also deals with the critical issues and recent studies based on the HMs biodetoxification using aquatic microorganisms.

Effect of processing method (natural, washed, honey, fermentation, maceration) on the availability of heavy metals in specialty coffee

The aim of this study was to determine the effect of various methods of processing, such as natural, washed, honey, anaerobic fermentation, and carbonic maceration, on the contents of heavy metals in green and roasted specialty coffees from various countries of origin (Ethiopia, Kenya, Rwanda, Burundi, Guatemala, Nicaragua, and Peru). The heavy metals aluminium (Al), nickel (Ni), chromium (Cr), cadmium (Cd), copper (Cu), and lead (Pb) were identified by a multi-element technique using inductively coupled plasma mass spectrometry. Mercury (Hg) content was determined by atomic absorption spectrometry. The processing method affected the contents of Hg, Al, Ni, Cr, Cd, and Pb in the green and roasted coffees (p < 0.001). Hg content varied in the green coffees processed by fermentation methods vs natural or washed methods (i.e. Rwandan and Guatemalan coffees). Cd content was highest in Guatemalan green coffee processed using carbonic maceration (0.062 mg/kg). Pb content differed between the Ethiopian and Rwandan roasted coffees, with the highest content in the washed method (0.252 mg/kg). The correlations between the contents of Cu and Al, Ni and Cr, and Pb and Cr were significant for both the roasted and green beans. In conclusion, the method of processing can affect the contents of heavy metals in green and roasted specialty coffees. Monitoring heavy metals when processing coffee with new methods, even though further processing such as roasting can substantially reduce their content in some cases, is therefore important.

Isolation and identification of metallotolerant bacteria with a potential biotechnological application

Mining has led to severe environmental pollution in countries with exhaustive mining production and inadequate industrial waste regulation. Microorganisms in contaminated sites, like mine tailings, have adapted to high concentrations of heavy metals, developing the capacity of reducing or removing them from these environments. Therefore, it is essential to thoroughly characterize bacteria present in these sites to find different ways of bioremediation. In this regard, in this study, an enrichment and isolation procedure were performed to isolate bacteria with lower nutritional requirements and high tolerance to Cu(II) and Fe(II) from two Sonoran River basin mining tails. Two Staphylococcus species and a Microbacterium ginsengisoli strain were isolated and identified from the San Felipe de Jesús mining tail. Also, three strains were isolated from the Nacozari de García mining tail: Burkholderia cenocepacia, Sphingomonas sp. and Staphylococcus warneri. Significant microbiological differences were found between the two sites. All these species exhibited tolerance up to 300 mg/L for Cu (II)-Fe (II) solutions, indicating their capacity to grow in these conditions. Moreover, a consortium of isolated bacteria was immobilized in two different biocomposites and the biocomposite with larger pore size achieved greater bacterial immobilization showcasing the potential of these bacteria in biotechnological applications.

Simulation study of a practical approach to enhance cadmium removal via biological treatment by controlling the concentration of MLSS

The fate of cadmium at the Muharram Aisha wastewater treatment plant in Karbala governorate, Iraq was studied using the TOXCHEM model. Cadmium, a known carcinogen, and is considered one of the most dangerous heavy metals and high concentrations, greater than permissible limits, were found in the treated wastewater. The plant operates using an activated sludge system and this was modeled via TOXCHEM with a sensitivity analysis carried out on the extended aeration system. Prior to analysis, the model was calibrated and validated for cadmium, with the adjustments leading to a mean square error (RMSE) and correlation coefficient (R) of 0.0001 and 0.81, respectively. The mass balance of cadmium in the Muharram Aisha treatment plant was found to be 4832.44 g/day (37.1726%) in the treated wastewater and 8164.52 g/day (62.804%) in the sludge, which indicated that the mix liquor suspended solid (MLSS) was the most sensitive factor. The sensitivity to cadmium was analyzed via MLSS in the extended aeration system and the results o indicated that the higher the MLSS concentration (mg/L), the greater the removal of cadmium in the treated wastewater. It was found that increasing the MLSS through a biological treatment method reduced the concentration of cadmium without the need for additional of any (potentially harmful) chemical treatments. The plant was subsequently operated for a period of 5 months with the MLSS increased from 1500 to 4500 mg/L, and this reduced the concentration of cadmium in the wastewater from 0.36 to 0.01 mg/L as a consequence. This research demonstrates how the novel application of TOXCHEM can be a useful tool in the reduction of heavy metal contamination in the environment.

Thiophene-based porphyrin polymers for Mercury (II) efficient removal in aqueous solution

Development of novel sulf-functionalized porous organic polymers (POPs) for Mercury (II) (Hg2+) removal is of great significant, but the adsorbents always suffered by the low adsorption capacity, stability, and efficiency for the reason that the common construction of functionalized POPs from the functionalized monomers or post-functionalization of the POPs always sacrifice the porosity. In this paper, porphyrin-based POPs with different heteroatoms were constructed through the aldehyde monomer (benzene, 2,5-thiophenedicarboxaldehyde and thieno[3,2-b]thiophene-2,5-dicarboxaldehyde) and pyrrole according to the Adler-Longo method. In this way, nitrogen (N) in pyrrole and sulfur (S) in thiophene structures were embed into the backbone structure of the polymers. The functional structures not only act as the linking building block into the stable cross-linking structure, but also offer abundant uncovered functional sites for Hg2+ adsorption, resulting the porphyrin-based POPs high Hg2+ capacity (1049 mg/g), removal efficiency (more than 99.9%), good reusability and selectivity for its highest heteroatoms contents. The adsorption mechanism confirmed the cooperative coordination of N in porphyrin and S in thiophene with Hg2+. This work confirmed the functional groups play more important role in heavy metal adsorption, and the embedded functional sites into backbone also promotes the stability and the adsorption performance.

Overview of environmental and economic viability of activated carbons derived from waste biomass for adsorptive water treatment applications

In adsorptive water treatment applications, the exploration of waste-derived activated carbon (AC) has gained substantial attention in scientific research. The use of waste materials as precursors for AC has gained attention due to its economic viability and potential to reduce the consumption of non-renewable resources. However, there is a lack of comprehensive literature regarding the costs and environmental impacts associated with the waste-based AC production and application. As sustainability practices gain importance, there has been an increase in research dedicated to estimating costs and conducting life cycle assessment (LCA) of AC production from waste sources. However, there is a need for thorough literature reviews that cover various methodologies and conclusions. The primary objective of this study is to provide a comprehensive overview and analysis of the economic and environmental factors related to the use of waste-derived AC in water treatment. LCA studies indicate that utilizing waste materials for AC production can lead to significant resource and energy savings compared to conventional methods relying on fossil resources. The cost of AC is influenced by factors such as precursor material cost, energy requirements during production (optimizable on an industrial scale), and properties of the resulting material. Additionally, the review emphasizes the significance of waste-based AC regeneration for sustainable viability. Evaluating the environmental and economic costs is crucial to support sustainability claims and avoid unsupported assertions. Overall, this study contributes to understanding the potential of waste-derived AC in water treatment and highlights the need for further research in this area.

Upcycling of recycled minerals from sewage sludge through black soldier fly larvae (Hermetia illucens): Impact on growth and mineral accumulation

Phosphorous (P) resources are finite. Sewage sludge recyclates (SSR) are not only of interest as plant fertilizer but also as potential source of minerals in animal nutrition. However, besides P and calcium (Ca), SSR contain heavy metals. Under EU legislation, the use of SSR derivatives in animal feed is not permitted, but given the need to improve nutrient recycling, it could be an environmentally sound future mineral source. Black soldier fly larvae (BSFL) convert low-grade biomass into valuable proteins and lipids, and accumulate minerals in their body. It was hypothesized that BSFL modify and increase their mineral content in response to feeding on SSR containing substrates. The objective was to evaluate the upcycling of minerals from SSR into agri-food nutrient cycles through BSFL. Growth, nutrient and mineral composition were compared in BSFL reared either on a modified Gainesville fly diet (FD) or on FD supplemented with either 4% of biochar (FD + BCH) or 3.6% of single-superphosphate (FD + SSP) recyclate (n = 6 BSFL rearing units/group). Larval mass, mineral and nutrient concentrations and yields were determined, and the bioaccumulation factor (BAF) was calculated. The FD + SSP substrate decreased specific growth rate and crude fat of BSFL (P < 0.05) compared to FD. The FD + SSP larvae had higher Ca and P contents and yields but the BAF for Ca was lowest. The FD + BCH larvae increased Ca, iron, cadmium and lead contents compared to FD. Larvae produced on FD + SSP showed lower lead and higher arsenic concentration than on FD + BCH. Frass of FD + BCH had higher heavy metal concentration than FD + SSP and FD (P < 0.05). Except for cadmium and manganese, the larval heavy metal concentration was below the legally permitted upper concentrations for feed. In conclusion, the SSR used could enrich BSFL with Ca and P but at the expense of growth. Due to the accumulation of Cd and Mn, BSFL or products thereof can only be a component of farmed animal feed whereas in BSFL frass heavy metal concentrations remained below the upper limit authorized by EU.

Mathematical and Statistical Evaluation of Reverse Osmosis in the Removal of Manganese as a Way to Achieve Sustainable Operating Parameters

Manganese is the Earth's crust's third most abundant transition metal. Decades of increased mining activities worldwide have inevitably led to the release of large amounts of this metal into the environment, specifically in water resources. Up to a certain level, manganese acts as an essential micronutrient to maintain health and support the growth and development of microorganisms, plants, and animals, while above a specific limit, manganese can cause toxicity in aquatic and terrestrial ecosystems. There are conventional ways to remove manganese from water, such as chemical precipitation, sorption, and biological methods. However, other treatments have yet to be studied much, such as reverse osmosis (RO), which has demonstrated its effectiveness in the removal of heavy metals and could be a suitable alternative for manganese removal if its energy consumption is reduced. This research presents mathematical and statistical modeling of the behavior of a system in laboratory-scale RO. The principal finding was that it is possible to remove Mn using the RO operated with low pressures without decreasing the sustainable removal efficiency. Reducing the operating costs of RO opens the possibility of implementing RO in different contexts where there are problems with water contamination and economic limitations.

Silanized fiberglass modified by carbon dots as novel and impressive adsorbent for aqueous heavy metal ion removal

This work discusses the application of a silanized fiberglass (SFG) modified by carbon dots (CDs) as an effective adsorbent for up-taking some heavy metal ions including lead (Pb²⁺), chromium (Cr³⁺), cadmium (Cd²⁺), cobalt (Co²⁺), and nickel (Ni²⁺) as pollutant in the aqueous solution by batch method. Removal tests were carried out after optimization of pH, contact time, initial concentration of metal ions, and CDs amount. The SFG modified with CDs (CDs-SFG) was applied for the removal of 10 ppm of each metal ion solution after 100 min and the corresponding results showed the removal efficiencies of 100, 93.2, 91.8, 90, and 88.3% for Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, and Ni²⁺, respectively. The adsorption capacity of CDs-SFG in the metal ion mixed solution was also evaluated, and the results indicated the same trend in the adsorption capacity for metal ions in the mixed solution, though with lower absolute values compared to the single metal solutions. Moreover, the selectivity of this adsorbent for the adsorption of Pb²⁺ was almost twice of other tested metal ions. The regeneration of the CDs-SFG showed that its adsorption capacity after five cycles was reduced about 3.9, 6.0, 6.8, 6.7, and 8.0% for Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, and Ni²⁺, respectively. Finally, the applicability of the CDs-SFG adsorbent was examined with the analysis of the metal ions in water and wastewater samples.

Microbe-Plant Interactions Targeting Metal Stress: New Dimensions for Bioremediation Applications

In the age of industrialization, numerous non-biodegradable pollutants like plastics, HMs, polychlorinated biphenyls, and various agrochemicals are a serious concern. These harmful toxic compounds pose a serious threat to food security because they enter the food chain through agricultural land and water. Physical and chemical techniques are used to remove HMs from contaminated soil. Microbial-metal interaction, a novel but underutilized strategy, might be used to lessen the stress caused by metals on plants. For reclaiming areas with high levels of heavy metal contamination, bioremediation is effective and environmentally friendly. In this study, the mechanism of action of endophytic bacteria that promote plant growth and survival in polluted soils-known as heavy metal-tolerant plant growth-promoting (HMT-PGP) microorganisms-and their function in the control of plant metal stress are examined. Numerous bacterial species, such as Arthrobacter, Bacillus, Burkholderia, Pseudomonas, and Stenotrophomonas, as well as a few fungi, such as Mucor, Talaromyces, Trichoderma, and Archaea, such as Natrialba and Haloferax, have also been identified as potent bioresources for biological clean-up. In this study, we additionally emphasize the role of plant growth-promoting bacteria (PGPB) in supporting the economical and environmentally friendly bioremediation of heavy hazardous metals. This study also emphasizes future potential and constraints, integrated metabolomics approaches, and the use of nanoparticles in microbial bioremediation for HMs.

Simulation of Internal Defects in TKX-50 Crystals

1,1'-Dihydroxy-5,5'-bi-tetrazolium dihydroxylamine salt (TKX-50) is a new type of high-energy low-sense explosive with great application value, but TKX-50 made directly from the reaction has problems such as irregular crystal morphology and relatively large length-diameter, and these factors seriously affect the sensitivity of TKX-50 and limit its large-scale application. The internal defects of TKX-50 crystals have a great influence on their weakness, and studying its related properties is of great theoretical significance and application value. To further investigate the microscopic properties of TKX-50 crystals and to explore the connection between microscopic parameters and macroscopic susceptibility, this paper reports the use of molecular dynamics simulations to construct TKX-50 crystal scaling models with three types of defects-vacancy, dislocation and doping-and conducts molecular dynamics simulations. The influence of TKX-50 crystal defects on the initiation bond length, density, bonding diatomic interaction energy, and cohesive energy density of the crystal was obtained. The simulation results show that the models with a higher bond length of the initiator bond and higher percentage activated the initiator's N-N bond and lowered the bond-linked diatomic energy, cohesive energy density, and density corresponding to higher crystal sensitivities. This led to a preliminary connection between TKX-50 microscopic model parameters and macroscopic susceptibility. The results of the study can provide a reference for the design of subsequent experiments, and the research method can be extended to the research work on other energy-containing materials.

Removal of cadmium and lead ions from aqueous solutions by novel dolomite-quartz@Fe3O4 nanocomposite fabricated as nanoadsorbent

The elimination of heavy metal ion contaminants from residual waters is critical to protect humans and the environment. The natural clay (dolomite and quartz) based composite Fe₃O₄ nanoparticles (DQ@Fe₃O₄) has been largely explored for this purpose. Experimental variables such as temperature, pH, heavy metal concentration, DQ@Fe₃O₄ dose, and contact time were optimized in details. The DQ@Fe₃O₄ nanocomposite was found to achieve maximum removals of 95.02% for Pb²⁺ and 86.89% for Cd²⁺, at optimal conditions: pH = 8.5, adsorbent dose = 2.8 g L^-1, the temperature = 25 °C, and contact time = 140 min, for 150 mg L^-1 heavy metal ion initial concentration. The Co-precipitation of dolomite-quartz by Fe₃O₄ nanoparticles was evidenced by SEM-EDS, TEM, AFM, FTIR, XRD, and TGA analyses. Further, the comparison to the theoretical predictions, of the adsorption kinetics, and at the equilibrium, of the composite, revealed that they fit, respectively to, the pseudo-second-order kinetic, and Langmuir isotherm. These both models were found to better describe the metal binding onto the DQ@Fe₃O₄ surface. This suggested a homogenous monolayer sorption dominated by surface complexation. Additionally, thermodynamic data have shown that the adsorption of heavy metal ions is considered a spontaneous and exothermic process. Moreover, Monte Carlo (MC) simulations were performed in order to elucidate the interactions occurring between the heavy metal ions and the DQ@Fe₃O₄ nanocomposite surface. A good correlation was found between the simulated and the experimental data. Moreover, based on the negative values of the adsorption energy (Eads), the adsorption process was confirmed to be spontaneous. In summary, the as-prepared DQ@Fe₃O₄ can be considered a low-cost-effective heavy metals adsorbent, and it has a great potential application for wastewater treatment.

Iron/iron oxide-based magneto-electrochemical sensors/biosensors for ensuring food safety: recent progress and challenges in environmental protection

Foodborne diseases have arisen due to the globalization of industry and the increase in urban population, which has led to increased demand for food and has ultimately endangered the quality of food. Foodborne diseases have caused some of the most common public health problems and led to significant social and economic issues worldwide. Food quality and safety are affected by microbial contaminants, growth-promoting feed additives (β-agonists and antibiotics), food allergens, and toxins in different stages from harvesting to storage and marketing of products. Electrochemical biosensors, due to their reduced size and portability, low cost, and low consumption of reagents and samples, can quickly provide valuable quantitative and qualitative information about food contamination. In this regard, using nanomaterials can increase the sensitivity of the assessment. Magnetic nanoparticle (MNP)-based biosensors, especially, are receiving significant attention due to their low-cost production, physicochemical stability, biocompatibility, and eco-friendly catalytic characteristics, along with magnetic, biological, chemical and electronic sensing features. Here, we provide a review on the application of iron-based magnetic nanoparticles in the electrochemical sensing of food contamination. The types of nanomaterials used in order to improve the methods and increase the sensitivity of the methods have been discussed. Then, we stated the advantages and limitations of each method and tried to state the research gaps for each platform/method. Finally, the role of microfluidic and smartphone-based methods in the rapid detection of food contamination is stated. Then, various techniques like label-free and labelled regimes for the sensitive monitoring of food contamination were surveyed. Next, the critical role of antibody, aptamer, peptide, enzyme, DNA, cells and so on for the construction of specific bioreceptors for individual and simultaneous recognition by electrochemical methods for food contamination were discussed. Finally, integration of novel technologies such as microfluidic and smartphones for the identification of food contaminations were investigated. It is important to point out that, in the last part of each sub-section, attained results of different reports for each strategy were compared and advantages/limitations were mentioned.

Reconstruction of heavy metal(loid) pollution history based on dendrochemistry in Jiuzhaigou World Natural Heritage site, southwestern China

Heavy metal(loid)s are widely regarded as important environmental pollutants and have attracted extensive attention. In addition to such areas with frequent human activities as cities and industrial areas, the heavy metal(loid) pollution in remote areas lacking long-term monitoring data also deserves attention. In this study, Chinese pine (Pinus tabuliformis) in Jiuzhaigou World Natural Heritage was sampled to analyze concentration of Pb, Zn, Cu, As, Cd, Co, Cr, and Ni and to reconstruct pollution history. Source analysis and evaluation of the potential ecological risk of heavy metal(loid)s were also performed. Results showed that Jiuzhaigou has been polluted by heavy metal(loid)s at a relatively high level and concentrations were the highest at the location with intensive human activities (Nuorilang). Tree growth was inhibited by increased heavy metal(loid) concentration and this situation was more pronounced at high concentrations. The increased heavy metal(loid) concentrations were attributed to human activities such as forest logging, infrastructure construction, and tourism development. Heavy metal(loid) pollution reached a very high level of ecological harm at Nuorilang and a high level of ecological harm in Shuzheng and Heye villages. Overall, even at low concentrations, we demonstrated that Chinese pine can be used not only as a bioindicator for heavy metal(loid) pollution but also to infer pollution history over a relative long-term period and to enhance our understanding of the biogeochemical cycle of heavy metal(loid)s in forest ecosystems.

A multifunctional adsorbent based on 2,3-dimercaptosuccinic acid/dopamine-modified magnetic iron oxide nanoparticles for the removal of heavy-metal ions

Overexploitation of nature by humans has led to an increasingly serious issue of heavy-metal water pollution. To reduce the threat of water pollution to humans and the environment, it is imperative to develop or improve the water treatment technology for heavy-metal-containing wastewater. Functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) have been widely used as effective adsorbents for the removal of heavy-metal ions from water owing to their high efficiency, low cost, selective adsorption ability, and recyclability. In this study, Fe₃O₄@DA-DMSA magnetic nanoparticles (FDDMs) were prepared by the functionalization of Fe₃O₄ MNPs with environmentally friendly dopamine (DA) and a heavy-metal detoxifying agent such as 2,3-dimercaptosuccinic acid (DMSA) for the efficient and rapid adsorption of Pb²⁺, Cu²⁺, and Cd²⁺, with maximum adsorption capacities of 187.62, 63.01, and 49.46 mg/g, respectively. FDDMs exhibited the best ability to remove Pb²⁺ with a maximum adsorption capacity than that of the most reported Fe₃O₄ MNP-related adsorbents. In actual wastewater and multi-component simulated water samples contaminated with Pb²⁺, Cu²⁺, and Cd²⁺, the as-prepared adsorbent maintained a good removal ability for Pb²⁺ with low influence by ionic strength and interfering ions, as well as exhibited an excellent selectivity. According to the results of batch experiments and X-ray photoelectron spectroscopy (XPS) analysis of the adsorbent before and after adsorption, the adsorption mechanism of the adsorbent for the removal of heavy-metal ions mainly involves coordination and ion exchange. In addition, the adsorbent exhibited a good regeneration performance. Therefore, FDDMs can be considered as a promising adsorbent for the treatment of heavy-metal wastewater.

Preparation and properties of phosphinic acid-functionalized polyacrylonitrile hollow fiber membrane for heavy metal adsorption

In this study, phosphorylated polyacrylonitrile hollow fiber membrane was synthesized by reacting aminated polyacrylonitrile hollow fiber membrane with phosphinic acid in a Mannich reaction. The batch single-factor measurements revealed that the phosphorylated polyacrylonitrile (PPAN) membrane had an outstanding ability for Hg²⁺ adsorption. Thermodynamic investigations indicated that the adsorption process was homogenous, and the theoretical maximum adsorption capacity predicted by the Langmuir model was 371.75 mg·g^-1. The PPAN membrane was able to successfully chelate Hg²⁺ ions and attain saturation in 4 h, demonstrating that the reaction was chemically controlled by the adsorption kinetics. Based on the FT-IR and XPS spectral characterization data, successful phosphinic acid group grafting was proven, and a plausible mechanism for Hg²⁺ adsorption by PPAN membranes was presented. Furthermore, the five adsorption-desorption cycle experiments revealed that PPAN hollow fiber membranes had outstanding reusability, indicating a possible use for removing heavy metal ions from wastewater.

Removal of Copper Ions from Wastewater: A Review

Copper pollution of the world's water resources is becoming increasingly serious and poses a serious threat to human health and aquatic ecosystems. With reported copper concentrations in wastewater ranging from approximately 2.5 mg/L to 10,000 mg/L, a summary of remediation techniques for different contamination scenarios is essential. Therefore, it is important to develop low-cost, feasible, and sustainable wastewater removal technologies. Various methods for the removal of heavy metals from wastewater have been extensively studied in recent years. This paper reviews the current methods used to treat Cu(II)-containing wastewater and evaluates these technologies and their health effects. These technologies include membrane separation, ion exchange, chemical precipitation, electrochemistry, adsorption, and biotechnology. Thus, in this paper, we review the efforts and technological advances made so far in the pursuit of more efficient removal and recovery of Cu(II) from industrial wastewater and compare the advantages and disadvantages of each technology in terms of research prospects, technical bottlenecks, and application scenarios. Meanwhile, this study points out that achieving low health risk effluent through technology coupling is the focus of future research.

A Green Approach Used for Heavy Metals 'Phytoremediation' Via Invasive Plant Species to Mitigate Environmental Pollution: A Review

Heavy metals (HMs) normally occur in nature and are rapidly released into ecosystems by anthropogenic activities, leading to a series of threats to plant productivity as well as human health. Phytoremediation is a clean, eco-friendly, and cost-effective method for reducing soil toxicity, particularly in weedy plants (invasive plant species (IPS)). This method provides a favorable tool for HM hyperaccumulation using invasive plants. Improving the phytoremediation strategy requires a profound knowledge of HM uptake and translocation as well as the development of resistance or tolerance to HMs. This review describes a comprehensive mechanism of uptake and translocation of HMs and their subsequent detoxification with the IPS via phytoremediation. Additionally, the improvement of phytoremediation through advanced biotechnological strategies, including genetic engineering, nanoparticles, microorganisms, CRISPR-Cas9, and protein basis, is discussed. In summary, this appraisal will provide a new platform for the uptake, translocation, and detoxification of HMs via the phytoremediation process of the IPS.

Biopolymer - A sustainable and efficacious material system for effluent removal

Undesired discharge of various effluents directly into the aquatic ecosystem can adversely affect water quality, endangering aquatic and terrestrial flora and fauna. Therefore, the conceptual design and fabrication of a sustainable system for alleviating the harmful toxins that are discharged into the atmosphere and water bodies using a green sustainable approach is a fundamental standpoint. Adsorptive removal of toxins (∼99% removal efficacy) is one of the most attractive and facile approaches for cleaner technologies that remediate the environmental impacts and provide a safe operating space. Recently, the introduction of biopolymers for the adsorptive abstraction of toxins from water has received considerable attention due to their eclectic accessibility, biodegradability, biocompatibility, non-toxicity, and enhanced removal efficacy (∼ 80-90% for electrospun fibers). This review summarizes the recent literature on the biosorption of various toxins by biopolymers and the possible interaction between the adsorbent and adsorbate, providing an in-depth perspective of the adsorption mechanism. Most of the observed results are explained in terms of (1) biopolymers classification and application, (2) toxicity of various effluents, (3) biopolymers in wastewater treatment and their removal mechanism, and (4) regeneration, reuse, and biodegradation of the adsorbent biopolymer.

Preparation and Characterization of Electrospun Poly(lactic acid)/Poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)/Silicon Dioxide Nanofibrous Adsorbents for Selective Copper (II) Ions Removal from Wastewater

The problem of industrial wastewater containing heavy metals is always a big concern, especially Cu²⁺, which interprets the soil activity in farmland and leaves a negative impact on the environment by damaging the health of animals. Various methods have been proposed as countermeasures against heavy-metal contaminations, and, as a part of this, an electrospun nanofibrous adsorption method for wastewater treatment is presented as an alternative. Poly(lactic acid) (PLA) is a biopolymer with an intrinsic hydrophobic property that has been considered one of the sustainable nanofibrous adsorbents for carrying adsorbate. Due to the hydrophobic nature of PLA, it is difficult to adsorb Cu²⁺ contained in wastewater. In this study, the hydrophilic PLA/poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG) nanofibrous adsorbents with different silicon dioxide (SiO₂) concentrations were successfully prepared by electrospinning. A hydrophilic group of PEG-PPG-PEG was imparted in PLA by the blending method. The prepared PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents were analyzed with their morphological, contact angle analysis, and chemical structure. The Cu²⁺ adsorption capacities of the different PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents were also investigated. The adsorption results indicated that the Cu²⁺ removal capacity of PLA/PEG-PPG-PEG/SiO₂ nanofibrous adsorbents was higher than that of pure ones. Additionally, as an affinity nanofibrous adsorbent, its adsorption capacity was maintained after multiple recycling processes (desorption and re-adsorption). It is expected to be a promising nanofibrous adsorbents that will adsorb Cu²⁺ for wastewater treatment.

Adsorption technique for the removal of heavy metals from wastewater using low-cost natural adsorbent

The primary goal of this study was to use low-cost adsorbents, this achieves by using pine cones as plant waste adsorbents in the treatment of industrial wastewater. In the experimental work of this study, a system of PVC horizontal pipes of 15cm diameter and 600 cm length without membranes was used. The polluted water values discharged in the system were 20, 40, 60, 80, and 100 L/hr. The effect of many hydraulic parameters (contact time, flow discharge, length of the pipe, and pressure) with environmental parameters (pH, TDS, TSS and electrical conductivity) was investigated in this continuous flow system. The sample of plant waste (pine cone) was treated and activated by ozonation, to manufacture new media with high porosity, activated carbon developed from pine cone (ACPC), and to determine the activity that produces the best results in the removal of heavy metals. To remove Fe+2 and Zn+2 ions from industrial wastewater, activated carbon was used as an adsorbent. Adsorption tests result in an exhibit that, the ACPC adsorbent had remarkable heavy metals removal efficiency. The most effective removal efficiency of 95% of Zn+2 was recorded at pH 7, 20 l/hr, and 5hrs. The higher removal efficiency of 96.67% of Fe+2 occurred at pH 6, 20 l/hr, and 5hr. The study also revealed that activated carbon devolved from pine cones can be adopted as a low-cost alternative for removing metal ions.

Removal of dyes, oils, alcohols, heavy metals and microplastics from water with superhydrophobic materials

A wide variety of pollutants can be currently found in water that are extremely difficult to remove due to their chemical composition and properties. A lot of effort has been made to tackle this issue that directly affects the environment. In this scenario, superhydrophobic surfaces, which have a water contact angle >150°, have emerged as an innovative technology that could be applied in different ways. Their environmental applications show promise in removing emerging pollutants from water. While the number of publications on superhydrophobic materials has remained largely unchanged since 2019, the number of articles on the environmental applications of superhydrophobic surfaces is still rising, corroborating the interest in this area. Herein, we briefly present the basis of superhydrophobicity and show the different materials that have been used to remove pollutants from water. We have identified five types of emerging pollutants that are efficiently removed by superhydrophobic materials: oils, microplastics, dyes, heavy metals, and ethanol. Finally, the future challenges of these applications are also discussed, considering the state of the art of the environmental applications of superhydrophobic materials.

Synthetic bacteria for the detection and bioremediation of heavy metals

Toxic heavy metal accumulation is one of anthropogenic environmental pollutions, which poses risks to human health and ecological systems. Conventional heavy metal remediation approaches rely on expensive chemical and physical processes leading to the formation and release of other toxic waste products. Instead, microbial bioremediation has gained interest as a promising and cost-effective alternative to conventional methods, but the genetic complexity of microorganisms and the lack of appropriate genetic engineering technologies have impeded the development of bioremediating microorganisms. Recently, the emerging synthetic biology opened a new avenue for microbial bioremediation research and development by addressing the challenges and providing novel tools for constructing bacteria with enhanced capabilities: rapid detection and degradation of heavy metals while enhanced tolerance to toxic heavy metals. Moreover, synthetic biology also offers new technologies to meet biosafety regulations since genetically modified microorganisms may disrupt natural ecosystems. In this review, we introduce the use of microorganisms developed based on synthetic biology technologies for the detection and detoxification of heavy metals. Additionally, this review explores the technical strategies developed to overcome the biosafety requirements associated with the use of genetically modified microorganisms.

Development of Ni(II) resistant S. cerevisiae and its application: Adsorption study and modeling

The study aims to develop Ni(II) resistant Saccharomyces cerevisiae to decontaminate high Ni(II) concentrations from an aqueous system. Initially, two different microorganisms were taken: Bacillus circulans MTCC 3161, Saccharomyces cerevisiae. For these two strains, the experiments were carried out for successive screening for survival/tolerance, minimum inhibitory concentration (MIC), and biosorption capacity for Ni(II) from an aqueous solution. Ni(II) resistant Saccharomyces cerevisiae AJ208 showed a MIC of 5500 mg/L for Ni(II). Nucleotide sequences of Saccharomyces cerevisiae AJ208 were deposited in the Gene bank. All experiments were conducted to determine the effects of various physical conditions, such as pH, age and volume of inoculum, temperature, and incubation time, the volume of fermentation medium. The characterization of the Saccharomyces cerevisiae AJ208 was carried out using SEM-EDAX, FTIR. The Langmuir isotherm and pseudo-second-order kinetic models are well fitted with the experimental data. The Langmuir maximum adsorption capacity is 170.06 mg/g. The thermodynamic studies showed the mechanism of Ni(II) removal is an endothermic and spontaneous reaction. The experimental data have been analyzed using statistical method (MLR) and Genetic algorithm (GA). This study reports the highest Ni(II) resistant Saccharomyces cerevisiae AJ208 (5000 mg/L) and also the feasibility of Ni(II) removal from 3000 mg/L initial Ni(II) concentration into an aqueous solution, which could be of great interest as a potential reference strain for Ni(II) removal.

Natural Zeolite Clinoptilolite Application in Wastewater Treatment: Methylene Blue, Zinc and Cadmium Abatement Tests and Kinetic Studies

In recent decades, several abatement techniques have been proposed for organic dyes and metal cations. In this scenario, adsorption is the most known and studied. Clinoptilolite was considered, since it is a zeolite with a relatively low cost (200-600 $ tons^-1) compared to the most well-known adsorbent used in wastewater treatment. In this work, Clinoptilolite was used for the adsorption of Methylene Blue (MB) at three different concentrations, namely, 100, 200, and 250 ppm. Furthermore, the adsorption capacity of the natural zeolite was compared with that of Activated Charcoal (250 ppm of MB). The two adsorbents were characterized by complementary techniques, such as N₂ physisorption at -196 °C, X-ray diffraction, and field emission scanning electron microscopy. During the adsorption tests, Clinoptilolite exhibited the best adsorption capacities at 100 ppm: the abatement reached 98% (t = 15 min). Both Clinoptilolite and Activated Charcoal, at 250 ppm, exhibited the same adsorption capacities, namely, 96%. Finally, at 250 ppm MB, the adsorption capacity of Clinoptilolite was analyzed with the copresence of Zn²⁺ and Cd²⁺ (10 ppm), and the adsorption capacities were compared with those of Activated Charcoal. The results showed that both adsorbents achieved 100% MB abatement (t = 40 min). However, cation adsorption reached a plateau after 120 min (Zn²⁺ = 86% and 57%; Cd²⁺ = 53% and 50%, for Activated Charcoal and Clinoptilolite, respectively) due to the preferential adsorption of MB molecules. Furthermore, kinetic studies were performed to fully investigate the adsorption mechanism. It was evidenced that the pseudo-second-order kinetic model is effective in describing the adsorption mechanism of both adsorbents, highlighting the chemical interaction between the adsorbent and adsorbate.

Mycotechnology to remove of metals from tannery and galvanic effluents - Fungal species from the Amazon and Atlantic Forest show high efficiency

Metals are considered one of the biggest environmental problems, due to their toxicity and the complexity of removal. This study evaluated the bioaccumulation capacity of water contaminating metals by fungal isolates of Lentinus and Panus species, to elucidate the bioremediation processes of metal contaminated effluents. Initially, tests were performed with fungal isolates using a mixture of metals, aluminum, iron, copper, lead, chromium, nickel and zinc. Lentinus crinitus 154L.21 was the most promising fungus for the removal of metals in the mixture. Based on these data, the potential application of this fungus for the treatment of galvanic and tannery effluents was evaluated. For galvanic effluent, no detectable copper, chromium, and nickel was removed; however, for tannery effluents, reductions in aluminum concentrations from 204.1 to 3.7 mg L^-1 (≅98% removal), chromium from 1199.6 to 20.4 mg L^-1 (≅98% removal) and iron from 22.6 mg L^-1 (100% removal) to an amount lower than the detection limit were observed. These data indicated that L. crinitus 154L.21 removes metals from industrial effluents, being an important route for bioremediation processes.

Mechanistic study of Hg(II) interaction with three different α-aminophosphonate adsorbents: Insights from batch experiments and theoretical calculations

Herein, efficient and potential chelating α-aminophosphonate based sorbents (AP-) derived from three different amine origins (aniline/anthranilic acid/O-phenylenediamine) to form AP-H, carboxylated and aminated enhanced aminophosphonate as AP-H, AP-COOH, and AP-NH₂ were synthesized via a facile method. The structure of the synthesized sorbents was elucidated using different techniques; elemental analysis (CHNP/O), FT-IR, NMR (¹H-, ¹³C and ³¹P NMR), TGA and BET. The fabricated sorbents were exploited for Hg(II) removal from aqueous solution via sorption properties. Isotherm fitted by Langmuir equation: the maximum sorption capacities at optimum pH 5.5, and T:25 ± 1 °C, were found to be 1.33, 1.23, and 1.15 mmol Hg g^-1 for AP-COOH, AP-NH₂, AP-H, respectively, which is roughly correlated with the active sites density and the hard/soft characteristics of adsorbents' reactive groups. Metal-ligand binding affinities are qualitatively rationalized in terms of hard and soft acids and bases (HSAB) theory. The interaction of Hg(II) (soft) has a stronger affinity to AP-COOH can be considered a softer base compared with reference material (AP-H) over than AP-NH₂ (hard). This sequence result showed opposite trends consistent with their reciprocal properties according to the steric effect modulates and the specific surface area. Thermodynamics analysis for absolute values of ΔH°, ΔS° and ΔG° afford the selectivity towards Hg(II) sorption with the following order: AP-COOH > AP-NH₂ >AP-H. Elution and regeneration was carried out by HCl solution and recycled for a minimum of five cycles, the sorption and desorption efficiencies are greater than 91%. Such sorbents exhibit good durability, stability and promising potential for Hg(II) removal. Finally, a new modelling technique for quantitative non-linear description and comparison of equivalent geographical positions in 3D space of extended relationships. Exothermic and spontaneous behavior were observed using a proposed Floatotherm that included the Van't Hoff parameters model.

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

Identification of differentially expressed genes for Pseudomonas sp. Cr13 stimulated by hexavalent chromium

Over exploitation of mineral resources has increasingly caused serious heavy metal contamination such as chromium (Cr). Cr(VI), the pathogenicity factor, is one of common environmental contaminants and widely known health hazards to living organisms. Therefore, it is urgent to control the polluted soil. Up to now, little is known about the regulatory mechanisms of Cr response in Pseudomonas sp. Cr13. In this study, transcriptome and differentially expressed genes in Pseudomonas sp. Cr13 strain was characterized by a comparison between Cr(VI)-treated sample and control sample using transcriptome sequencing approach. In total, 2974 genes were annotated, including 1245 (1154 down-regulated genes and 91 up-regulated genes) differentially expressed genes (DEGs). All DEGs could be assigned to 29 pathways, of which pathways related to amino acid metabolism, carbohydrate metabolism, energy metabolism and signal transduction mechanism were significantly enriched in Pseudomonas sp. Cr13. A possible mechanism for Cr toxicity response might be an active efflux which utilized a heavy metal translocating P-type ATPase to lower the intracellular Cr concentration. The down-regulated genes related to the antioxidant defense system had a key role in Cr reduction, such as SodA, Gst, osmC, BtuE, KatE, csdA and AhpC. The proteins that were visibly up-regulated, were likely to involve in alleviating Cr(VI) stress, and the significantly down-regulated genes such as MarR, Lrp, FhlA, GntR, HrcA, LysR family genes, were likely to reduce Cr(VI) induced oxidative stress. In addition, real-time quantitative PCR was used to analyze the expression patterns of some Cr responsive genes. This study reported the first identification of Cr responsive genes, and inferred the underlying regulatory mechanisms of response to Cr(VI) stress in Pseudomonas sp. Cr13.

Preparation of new MOF-808/chitosan composite for Cr(VI) adsorption from aqueous solution: Experimental and DFT study

In this study, a series of Zirconium-based MOF and chitosan composites (MOF-808/chitosan) were synthesized as efficient adsorbent for Cr(VI) ions elimination from aqueous solution. MOF-808/chitosan structure and morphology was characterized by FE-SEM, EDX, XRD, BET, zeta potential analysis, FT-IR, XPS techniques. The kinetic studies ascertained that Cr(VI) adsorption over MOF-808/chitosan followed pseudo-second-order kinetic model. The adsorption isotherms fitted the Langmuir isotherm model, implying on homogeneously adsorption of Cr(VI) on the surface of MOF-808/chitosan. According to the Langmuir model, the maximum capacity was obtained to be 320.0 mg/g at pH 5. Thermodynamic investigation proposed spontaneous (ΔG° < 0), disordered (ΔS° > 0) and endothermic (ΔH° > 0) for adsorption process. Besides, MOF-808/chitosan displayed an appropriate reusability for the elimination of Cr(VI) ions from their aqueous solutions for six successive cycles. DFT study of the adsorption process displayed and confirmed the role of hydrogen bonding and electrostatic attraction simultaneously.

Application of Nanocatalysts in Advanced Oxidation Processes for Wastewater Purification: Challenges and Future Prospects

The increase in population demands for industrialization and urbanization which led to the introduction of novel hazardous chemicals in our environment. The most significant parts of these harmful substances found in water bodies remain in the background, causing a health risk to humans and animals. It is critical to remove these toxic chemicals from the wastewater to keep a cleaner and greener environment. Hence, wastewater treatment is a challenging area these days to manage liquid wastes effectively. Therefore, scientists are in search of novel technologies to treat and recycle wastewater, and nanotechnology is one of them, thanks to the potential of nanoparticles to effectively clean wastewater while also being ecologically benign. However, there is relatively little information about nanocatalysts’ applicability, efficacy, and challenges for future applications in wastewater purification. This review paper is designed to summarize the recent studies on applying various types of nanocatalysts for wastewater purification. This review paper highlights innovative work utilizing nanocatalysts for wastewater applications and identifies issues and challenges to overcome for the practical implementation of nanocatalysts for wastewater treatment.

Air Pollutants Removal Using Biofiltration Technique: A Challenge at the Frontiers of Sustainable Environment

Air pollution is a central problem faced by industries during the production process. The control of this pollution is essential for the environment and living organisms as it creates harmful effects. Biofiltration is a current pollution management strategy that concerns removing odor, volatile organic compounds (VOCs), and other pollutants from the air. Recently, this approach has earned vogue globally due to its low-cost and straightforward technique, effortless function, high reduction efficacy, less energy necessity, and residual consequences not needing additional remedy. There is a critical requirement to consider sustainable machinery to decrease the pollutants arising within air and water sources. For managing these different kinds of pollutant reductions, biofiltration techniques have been utilized. The contaminants are adsorbed upon the medium exterior and are metabolized to benign outcomes through immobilized microbes. Biofiltration-based designs have appeared advantageous in terminating dangerous pollutants from wastewater or contaminated air in recent years. Biofiltration uses the possibilities of microbial approaches (bacteria and fungi) to lessen the broad range of compounds and VOCs. In this review, we have discussed a general introduction based on biofiltration and the classification of air pollutants based on different sources. The history of biofiltration and other mechanisms used in biofiltration techniques have been discussed. Further, the crucial factors of biofilters that affect the performance of biofiltration techniques have been discussed in detail. Finally, we concluded the topic with current challenges and future prospects.