Adsorption characteristics of magnetic nanoparticles coated mixed fungal biomass for toxic Cr(VI) ions in aquatic environment

Implementing magnetically-active Sn-based nanocomposites in hexavalent chromium removal from drinking water

A novel nanocomposite consisting of Fe3O4-loaded tin oxyhydroxy-chloride is demonstrated as an efficient adsorbent for the removal of hexavalent chromium in compliance to the new drinking water regulation. This study introduces a continuous-flow production of the nanocomposite through the separate synthesis of (i) 40 nm Fe3O4 nanoparticles and (ii) multilayered spherical arrangements of a tin hydroxy-chloride identified as abhurite, before the application of a wet-blending process. The homogeneous distribution of Fe3O4 nanoparticles on the abhurite's morphology, features nanocomposite with magnetic response whereas the 10 % loaded nanocomposite preserves a Cr(VI) uptake capacity of 7.2 mg/g for residual concentrations below 25 μg/L. Kinetic and thermodynamic examination of the uptake evolution indicates a relative rapid Cr(VI) capture dominated by interparticle diffusion and a spontaneous endothermic process mediated by reduction to Cr(III). The efficiency of the optimized nanocomposite was validated in a pilot unit operating in a sequence of a stirring reactor and a rotary magnetic separator showing an alternative and competitive application path than typical fixed-bed filtration, which is supported by the absence of any acute cellular toxicity according to human kidney cell viability tests.

Efficient removal of hexavalent chromium from water by Bacillus sp. Y2-7 with production of extracellular polymeric substances

Bioremediation is an environmentally friendly technology for the treatment of chromium-contaminated sites. Here, a hexavalent chromium [Cr(VI)]-resistant strain was isolated from oil-contaminated soil and designated as Bacillus sp. Y2-7 based on 16S rDNA sequence characterization. The effects of various factors including inoculation dose, pH value, glucose concentration, and temperature on Cr(VI) removal rates were then evaluated. Based on the response surface methodology, optimal Cr(VI) removal efficiency (above 90%) could be achieved at an initial Cr(VI) concentration of 155.0 mg·L-1, glucose concentration of 11.479 g·L-1, and pH of 7.1. The potential removal mechanisms of Cr(VI) by strain Y2-7 were also supposed. The contents of polysaccharide and protein in extracellular polymer (EPS) of strain Y2-7 decreased slowly after cultured with Cr(VI) of 15 mg·L-1 from 1 to 7 days. We thus inferred that EPS bonded with Cr(VI) and underwent morphological changes in water. Molecular operating environment (MOE) analysis suggested that macromolecular protein complexes in Bacillus sp. Y2-7 and hexavalent chromium could establish hydrogen bonds. Collectively, our findings indicate that Bacillus sp. Y2-7 is an excellent bacterial candidate for chromium bioremediation.

"Green" electrostatic droplet-assisted forming cellulose microspheres with excellent structural controllability and stability for efficient Cr(VI) removal

This study presents a novel and environmentally friendly method for producing cellulose microspheres (CM) with controllable morphology and size using electrostatic droplets. The traditional droplet method for CM production requires complex equipment and harmful reagents. In contrast, the proposed method offers a simple electrostatic droplet approach to fabricate CM10 at 10 kV, which exhibited a smaller volume, linear microscopic morphology, and a larger specific surface area, with a 36.60 % improvement compared to CM0 (prepared at 0 kV). CM10 also demonstrated excellent underwater structural stability, recovering in just 0.5 s, and exhibited the highest adsorption capacity for Cr(VI) at 190.16 mg/g, a 72.15 % improvement over CM0. This enhanced adsorption capacity can be attributed to the unique structure of CM10 and the introduction of more amino groups. Moreover, CM10 displayed good cyclic adsorption capacity and high dynamic adsorption efficiency, making it highly suitable for practical applications. CM10 exhibited remarkable adsorption capacity, stability, and practical value in treating Cr(VI) wastewater. This work proposes a simple and eco-friendly method for producing CM with excellent structural controllability and stability, providing an effective route for wastewater treatment.

Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption

Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 °C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH.

High nitrogen content bimolecular co-functionalized graphene nanoflakes for hypertoxic Cr(VI) removal: Insights into adsorption behavior and mechanisms

The proven high carcinogenicity to humans and high destructive force to the environment determine the extreme urgency of eliminating hypertoxic Cr(VI) in water bodies. Herein, a route of room temperature synthesis and secondary grafting was proposed to fabricate graphene oxide-based nanoadsorbent co-functionalized with polydopamine and branched polyethyleneimine (GOPP) to remove Cr(VI). The flexible decoration of polydopamine and polyethyleneimine on GO flakes could gradually enhance the amount of N-containing functional groups and realize selective removal of Cr(VI) with the maximum experimental adsorption capacity of 564.7 mg/g, displaying a significantly high separation factor against alkali metal, alkaline earth metal, and other transition metal ions. Various combination mechanisms, such as electrostatic attraction, reduction, complexation, and hydrogen bonding, were demonstrated to be involved in the adsorption process of Cr(VI) by XPS, ESP, and DFT calculations. And the interaction energies of the five protonated configurations of primary amine, tertiary amine, secondary amine, imine, and secondary amine on the ring with HCrO4- were: -22.66, -12.08, -24.92, -24.26, -27.64 kcal/mol. In the actual industrial wastewater study, a Cr(VI) removal rate of 85.8% was realized. This work provided a viable idea for the elimination of Cr(VI) and was expected to be applied in the field of wastewater treatment.

Development of silver oxide-loaded reduced graphene oxide nanohybrids for enhanced photocatalytic activity under visible light in aqueous solutions

We report on the synthesis of silver oxide/reduced graphene oxide nanocomposites (Ag/rGO NCs) using a hydrothermal technique. This paper presents a simple method for synthesizing Ag/rGO hybrid nanocomposites, which can be used for environmentally treating hazardous organic pollutants. The photocatalytic degradation of model artificial Rhodamine B dye and bisphenol A was assessed under visible light illumination. The crystallinity, binding energy, and surface morphologies of the synthesized samples were determined. The silver oxide loading sample resulted in a decrease in the rGO crystallite size. SEM and TEM images demonstrate strong adhesion of the Ag NPs to the rGO sheets. XPS analysis validated the binding energy and elemental composition of the Ag/rGO hybrid nanocomposites. The objective of the experiment was to enhance the photocatalytic efficiency of rGO in the visible region using Ag nanoparticles. The synthesized nanocomposites in the visible region exhibited good photodegradation percentages of approximately 97.5% and 98.6% after 120 min of irradiation for pure rGO, Ag NPs, and Ag/rGO nanohybrid, respectively. Furthermore, the Ag/rGO nanohybrid maintained their degradation ability for up to three cycles. The synthesized Ag/rGO nanohybrid demonstrated enhanced photocatalytic activity, expanding their potential for environmental remediation. Based on the investigations, Ag/rGO nanohybrid proved to be an effective photocatalyst and holds promise as an ideal material for future applications in preventing water pollution.

Eco-friendly approaches of mycosynthesized copper oxide nanoparticles (CuONPs) using Pleurotus citrinopileatus mushroom extracts and their biological applications

This current study aims to develop a unique biomaterial that can fight against oxidative stress and microbial infections without causing any harm. As a result, an easy-to-make, environment-friendly, long-lasting, and non-toxic copper oxide nanoparticle (CuONP) was synthesized using an edible mushroom Pleurotus citrinopileatus extract. The UV-visa spectroscopy analyses reflected a sharp absorbance peak at 250 nm. The FTIR, XRD, SEM, HR-TEM, and EDX instrumental tools were used to characterize the myco-produced CuONPs. The face-centred cubic (FCC) CuONPs were found to have diffraction peaks at the planes of (110), (002), (111), (112), (020), (202), (113), (310), (220), and (004). The HR-TEM result showed the particles having a spherical structure and an average nanoparticles size of 20 nm. The antimicrobial activity results expressed the broad spectrum of antibacterial effect and the better growth inhibition zone was recorded in P. aeruginosa (8.3 ± 0.1), E. coli (7.4 ± 0.3), K. pneumoniae (7.2 ± 0.1), S. aureus (7.1 ± 0.3), S. pneumoniae (6.3 ± 0.2), and B. cereus (6.2 ± 0.3). The cytotoxicity efficacy of myco-synthesized CuONPs tested against a cancer cell line (HT-29) observed the best result in low doses of mushroom extract (45.62 μg/mL). Based on the outcome of the study suggests that the mycosynthesized CuONPs using Pleurotus mushroom extract might serve as an alternative agent for biomedical applications in the near future.

Flax fiber based semicarbazide biosorbent for removal of Cr(VI) and Alizarin Red S dye from wastewater

In the present study, flax fiber based semicarbazide biosorbent was prepared in two successive steps. In the first step, flax fibers were oxidized using potassium periodate (KIO4) to yield diadehyde cellulose (DAC). Dialdehyde cellulose was, then, refluxed with semicarbazide.HCl to produce the semicarbazide functionalized dialdehyde cellulose (DAC@SC). The prepared DAC@SC biosorbent was characterized using Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis (C:H:N), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The DAC@SC biosorbent was applied for the removal of the hexavalent chromium (Cr(VI)) ions and the alizarin red S (ARS) anionic dye (individually and in mixture). Experimental variables such as temperature, pH, and concentrations were optimized in detail. The monolayer adsorption capacities from the Langmuir isotherm model were 97.4 mg/g and 18.84 for Cr(VI) and ARS, respectively. The adsorption kinetics of DAC@SC indicated that the adsorption process fit PSO kinetic model. The obtained negative values of ΔG and ΔH indicated that the adsorption of Cr(VI) and ARS onto DAC@SC is a spontaneous and exothermic process. The DAC@SC biocomposite was successfully applied for the removal of Cr(VI) and ARS from synthetic effluents and real wastewater samples with a recovery (R, %) more than 90%. The prepared DAC@SC was regenerated using 0.1 M K2CO3 eluent. The plausible adsorption mechanism of Cr(VI) and ARS onto the surface of DAC@SC biocomposite was elucidated.

Purification of domestic laundry wastewater in an integrated treatment system consists of coagulation and ultrafiltration membrane process

An integrated unit to purify and reuse domestic laundry wastewater consisting of coagulation, sand filtration, carbon adsorption, and ultrafiltration process is developed. Chitosan and Ameztreat 102 polyamine were used as coagulants and their treatability was measured by color, turbidity and concentration of Linear Alkylbenzene Sulphonates (LAS) at various operation conditions. As a result of the trial studies, the maximum removal efficiency was attained as (i) for Chitosan- 98.2% color, 99.3% turbidity, 100% LAS removal efficiency; (ii) for Polyamine-88% color, 99% turbidity, 100% LAS. The transport mechanism of the pollutant towards the coagulant was described using kinetic models. The thickener area calculated is 0.2436 m² for the flow rate of 100 L/h by Kynch theory. The results were recommended that the laundry wastewater be efficiently treated in the proposed treatment train and could be reused effectively.

Electrochemical detection of copper(II) in environmental samples using Penicillium sp. IITISM_ANK1 based biosensor

Detection of toxic metals at the lowest of their concentration in a variety of matrices has become a necessity due to the widespread and persistent nature of the contaminant. In this context, biosensors provide a viable alternative to the large sophisticated instrumentation. This study focuses on the development of a cost-effective fungal biomass-based biosensor that can be used for the detection of Cu(II). The fungal cells were pretreated with formaldehyde and studied with various spectroscopic studies. It was observed that the carbonyl groups along with amine groups played role in the sorption of copper ions which were stripped in an electrolytic solution to quantify the metal. Herein the dried fungal biomass was chemically activated and used to prepare a novel graphite paste electrode by repurposing a plastic pipette tip. The factors affecting the detection signal were optimized in further study. The electrochemical characterization revealed that the prepared bio-electrode was capable of detecting Cu in the range of 1 × 10^-7 M to 2 × 10^-5 M.

A review on the applicability of adsorption techniques for remediation of recalcitrant pesticides

Pesticide has revolutionised the agricultural industry by reducing yield losses and by enhancing productivity. But indiscriminate usage of such chemicals can negatively impact human health and ecosystem balance as certain pesticides can be recalcitrant in nature. Out of some of the suggested sustainable techniques to remove the pesticide load from the environment, adsorption is found to be highly efficient and can also be implemented on a large scale. It has been observed that natural adsorption that takes place after the application of the pesticide is not enough to reduce the pesticide load, hence, adsorbents like activated carbon, plant-based adsorbents, agricultural by-products, silica materials, polymeric adsorbents, metal organic framework etc are being experimented upon. It is becoming increasingly important to choose adsorbents which will not leave any secondary pollutant after treatment and the cost of production of such adsorbent should be feasible. In this review paper, it has been established that certain adsorbent like biochar, hydrochar, resin, metal organic framework etc can efficiently remove pesticides namely chlorpyrifos, diazinon, 2,4-Dichlorophenoxyacetic Acid, atrazine, fipronil, imidacloprid etc. The mechanism of adsorption, thermodynamics and kinetic part have been discussed in detail with respect to the pesticide and adsorbent under discussion. The reason behind choosing an adsorbent for the removal of a particular pesticide have also been explained. It is further highly recommended to carry out a cost analysis before implementing an absorbent because inspite of its efficacy, it might not be cost effective to use it for a particular type of pesticide or contaminant.

Adsorption mechanism of Cr(VI) on woody-activated carbons

To provide guidance for the selection of woody-activated carbon in the treatment of wastewater containing hexavalent chromium (Cr(VI)), the adsorption tests on two varieties of commercial woody-activated carbon powder from different manufacturers were carried out. The physicochemical properties and structural characteristics of activated carbon were studied by using elemental, chemical, and instrumental analyses. The adsorption mechanism of Cr(VI) was discussed by investigating the factors affecting the removal of hexavalent chromium. The two kinds of woody-activated carbon have microporous and mesoporous structures. Commercial woody-activated carbon No.1 (ACI) has a more extensive specific surface area and a better-developed pore structure. While ACI exhibits a higher adsorption capability when the content of Cr(VI) is high, commercial woody-activated carbon No.2 (AC) can remove hexavalent chromium fast when the concentration is low. A rise in pH value is not helpful for the materials to remove Cr(VI) from solutions. For Cr(VI) removal, the optimum pH value is 2. The adsorption of Cr(VI) by AC and ACI followed the pseudo-second-order kinetic model and Langmuir isothermal adsorption equation. The maximum adsorption value of Cr(VI) is 154.56 mg/g for AC and 241.55 mg/g for ACI. There is chemical adsorption during the Cr(VI) removal. A lot of Cr (Ⅲ) was formed by Cr(VI). The abundance of pores and the reducing ability of the materials are essential for the removal of Cr(VI).

Constructing Z-scheme g-C3N4/TiO2 heterostructure for promoting degradation of the hazardous dye pollutants

The use of dyes and segments has increased widely in recent years, but it poses a serious health risk to ecosystems. In this work, TiO₂ and two-dimensional g-C₃N₄ nanosheets (g-CN) were fabricated through co-precipitation and thermal polymerization technique, respectively. The g-CN-TiO₂ photocatalyst (1: 3, 2: 2, 3: 1) in various weight percentages was prepared using a simple impregnation process. The photocatalytic behaviour of the g-CN, TiO₂ NPs, and different weight percentages of g-CN-TiO₂ photocatalyst was evaluated against methylene blue (MB) dye under UV-visible light illumination. Compared to pristine and other weight percentages of the g-CN-TiO₂ nanocomposite, the optimized g-CN-TiO₂ nanocomposite (3:1) showed promoted performance against MB dye. The enriched catalytic efficiency can be accredited to the low amount of TiO₂ nanoparticles deposited on gCN nanosheets, possibly due to the boosted transport properties of the electron-hole pairs. The enriched photocatalytic behaviour can be attributed to the development of the Z-scheme system between TiO₂ and g-CN. The current study is an outstanding demonstration of the development of maximum catalytic efficiency for destroying hazardous chemical dyes.

Recent advances in the construction of biocomposites based on fungal mycelia

In recent years, environmental problems have become increasingly serious, significantly effecting the ecosystem and human health. To deal with the problem of environmental pollution in an eco-conscious way, sustainable composite biomaterials are being produced. Mycelium-based composite biomaterials combine biological systems with substrates such as nanomaterials or agricultural and industrial wastes, which can complement each other's advantages or turn waste into a useful resource. Such materials can solve practical wastewater problems as well as replace plastic products, thus reducing plastic pollution and contributing to the green transition of the environment. In this review, we summarized the recent findings of studies on these materials, indicating future research directions.

Sodium hydroxide pre-treated Aspergillus flavus biomass for the removal of reactive black 5 and its toxicity evaluation

The present study was focused on the removal of Reactive Black 5 (RB5) from aqueous solution using pre treated Aspergillus flavus as a biosorbent. Pre-treatment of fungal biomass with 0.1 M sodium hydroxide facilitated the removal of dye effectively when compared to untreated fungal biomass. Optimum biosorption conditions for RB5 removal was determined as a function of dye concentration (50-400 mg/L), biosorbent concentration (100-500 mg/L), incubation time (1-7hrs), pH (3-8) and temperature (20-50 °C). At the optimum conditions, the maximum removal efficiency of RB5 achieved by NaOH pretreated A. flavus was 91%. The dye removal was studied kinetically and it obeys the pseudo-second order model and the experimental equilibrium data well fitted the Langmuir isotherm indicating monolayer adsorption of dye molecules on the biosorbent. The thermodynamic parameters such as a change in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were calculated and negative values of ΔG suggested that the dye removal process was spontaneous at all temperatures. Furthermore, the values of ΔH revealed that the adsorption process was endothermic. Recovery of RB5 from the fungal biomass was effective using 0.1 M Na₂CO₃ as an eluent. The interaction of adsorbate with biosorbent was analyzed using UV-Vis and FT-IR spectroscopy, SEM and XRD analyses. Phytotoxicity and microbial toxicity studies revealed the non-toxic nature of the treated dye solution. Hence, the fungal biomass pretreated with NaOH was efficient in decolorizing RB5 as well as composite raw industrial effluent generated from dyeing industries.

Reduction of sulphur dioxide emission into the environment by adsorption on enhanced α-hematite surface

The top priority of the sustainable development goals is to improve the quality of the environment for better living. Sulphur dioxide is considered more hazardous than any other gases that pollute the environment and harm the well-being of organisms. In 2019, India alone accounted for 21% of the world's SO₂ emissions. Strict action is required to reduce maximum levels of SO₂ emission to the atmosphere to improve the total air quality. To reduce SO₂ emissions more effectively, in this study, α-hematite was chemically activated by using 5% NaOH and C₂H₅OH with the help of a double bed adsorption column. The adsorbent properties of α-hematite were studied by Brunauer-Emmett-Teller isotherm, which revealed a high surface area (539 m² g^-1), and pore size (2.3125 nm) and high volume in the pore (0.0293432 cm³ mg^-1). FTIR confirmed that the SO₂ particulate on the surface of the adsorbent with an adsorption capacity of 95%. The operating temperature of 40-50 °C was optimal for the chemical adsorption. It was found that the inlet concentration (64 mg m^-3) of SO₂ decreases as the adsorption of SO₂ increases. Trace SO₂ was well-adsorbed by the adsorbent, which resulted in a mass transfer zone. Freundlich's adsorption spectrum was more fit for low concentrated SO₂ than Langmuir isotherm. The results indicate that the environmental emission of SO₂ can be reduced with chemically enhanced α-hematite.

Biosorption and adsorption isotherm of chromium (VI) ions in aqueous solution using soil bacteria Bacillus amyloliquefaciens

This study looked at the development of effective biosorbents to recover the most toxic elements from industrial water. B. amyloliquefaciens was isolated from marine soils showing extreme resistance to Chromium (Cr(VI)) ions. During the 60 min of contact time, 79.90% Cr(VI) was adsorbed from the aqueous solution. The impact of important factors such as biomass concentration, pH of the medium, and initial metal ions concentration on biosorption rate was also examined. The desorption study indicated that 1 M HCl (91.24%) was superior to 0.5 M HCl (74.81%), 1 M NaOH (64.96%), and distilled water (3.66%). Based on the Langmuir model, the maximum adsorption capacity of the bio-absorbent was determined to be 48.44 mg/g. The absorption mechanism was identified as monolayer, and 1/n from the Freundlich model falls within 1, thus indicating favorable adsorption. Based on the findings of the present study, the soil bacterium B. amyloliquefaciens was found to be the best alternative and could be used to develop strategies for managing existing environmental pollution through biosorption.

A critical and recent developments on adsorption technique for removal of heavy metals from wastewater-A review

This review provides a quantitative description of the nano-adsorbent processing and its viability against wastewater detoxification by extracting heavy metal ions. The impact of nano-adsorbent functionalities on specific essential attributes such as the surface area, segregation, and adsorption capacity were comprehensively evaluated. A detailed analysis has been presented on the characteristics of nanomaterials through their limited resistance to adsorb some heavy metal ions. Experimental variables such as the adsorbent dosage, pH, substrate concentration, response duration, temperature, and electrostatic force that influence the uptake of metal ions have been studied. Besides, separate models for the adsorption kinetics and isothermal adsorption have been investigated to understand the mechanism behind adsorption. Here, we reviewed the different adsorbent materials with nano-based techniques for the removal of heavy metals from wastewater and especially highlighted the nano adsorption technique. The influencing factors such as pH, temperature, dosage time, sorbent dosage, adsorption capacities, ion concentration, and mechanisms related to the removal of heavy metals by nano composites are highlighted. Lastly, the application potentials and challenges of nano adsorption for environmental remediation are discussed. This critical review would benefit engineers, chemists, and environmental scientists involved in the utilization of nanomaterials for wastewater treatment.

Amine-bilayer-functionalized cellulose-chitosan composite hydrogel for the efficient uptake of hazardous metal cations and catalysis in polluted water

Herein, we represent a novel ecofriendly bilayer-amine group incorporated microcrystalline cellulose (MCC)/chitosan (CS) hydrogel, fabricated via integrating polydopamine (PDA) and polyethyleneimine (PEI) for reliable and effective extraction of copper (Cu²⁺), zinc (Zn²⁺), and nickel (Ni²⁺) ions from effluents. Owing to abundant adsorptive sites, the MCC-PDA-PEI/CS-PDA-PEI hydrogel showed excellent Cu²⁺, Zn²⁺, and Ni²⁺ adsorbabilities of ~434.8, ~277.7, and ~261.8 mg/g, respectively, in a single-ion adsorption system with the adsorption kinetics and isotherm complied with pseudo-second-order and Langmuir models, respectively. In a multi-ion adsorption system, hydrogel removes mixed metal cations with slightly higher selectivity for Cu²⁺. In accordance with X-ray photoelectron and Fourier-transform-infrared spectrometric analyses, a plausible binding mechanism of metal cations on the as-prepared hydrogel was proposed by chelation between hydrogel functional groups and metal ions. In the repetitive adsorption/desorption experiments, the hydrogel retained >40% metal ion adsorption and desorption capacities after four cycles. Furthermore, the Cu²⁺-adsorbing hydrogel could serve as a support for the in situ development of Cu nanoparticles, which showed excellent catalytic performance as demonstrated by the transformation of 4-nitrophenol (4-NP) to 4-aminophenol. This work provides a novel ecofriendly, reusable, and highly-efficient adsorbent, as well as a biocatalyst for remediation of heavy metal cations and 4-NP polluted effluents.

Integrated network analysis reveals that exogenous cadmium-tolerant endophytic bacteria inhibit cadmium uptake in rice

Most previous studies have focused on the diversity and species richness of microbial communities, however, understanding the interactions between species and detecting key functional members of the community can help us better understand how microorganisms perform their functions. In this study, the response of the rice plant microbial community to the inoculation of cadmium-resistant endophytic bacterium R5 (Stenotrophomonas) was investigated for the first time using a microbial phylogenetic molecular ecological network. The results showed that inoculation of R5 changed the topological characteristics of the microbial network in rice plants, with the resulting network displaying stronger complexity and interaction in roots and aboveground parts, indicating that inoculation of R5 provided favorable conditions for microbial interactions. In addition, these interactions may be related to the absorption and transportation of cadmium by rice. Under the exogenous addition of R5, the network interactions of the rice plant microbial community were more inclined to cooperation. Both in the roots and aboveground parts of rice, the plant Cd content showed a decrease as the complexity and connectivity of the network increased, suggesting that complex microbial networks may be more beneficial to rice than simple microbial networks because as they were more adaptive and resistant to unfavorable environments. After inoculation with the R5 strain, the negative interaction with Cd content in rice plants increased significantly, and there might be more synergy between the microbial community and plants to jointly inhibit the absorption and transportation of Cd.

Microwave-assisted thermochemical conversion of Zr-FeOOH nanorods to Zr-ZnFe2O4 nanorods for bacterial disinfection and photo-Fenton catalytic degradation of organic pollutants

Herein, we report a CoO_x-loaded Zr-doped ZnFe₂O₄ (CoO_x/Zr-ZFO) NR photocatalyst synthesized by successive microwave and wet impregnation methods for bacterial inactivation and degradation of organic pollutants. For the first time, microwave treatment was used for Zn attachment on hydrothermally synthesized self-assembled Zr-FeOOH NRs to produce Zr-doped ZnFe₂O₄ (Zr-ZFO) NRs. The lowest bandgap energy (1.96 eV) enables for significant absorption in the visible light region, which helps to improve bacteria degradation inactivation efficiency. Further, various metal oxides (Cu, Ag and Co) were loaded onto the surface of photocatalysts (Zr-ZFO NRs) by a wet impregnation method. As-synthesized CoO_x/Zr-ZFO-3 NRs were systematically characterized and used as photocatalysts for inactivation of E. coli and S. aureus and degradation of organic pollutants. The CoO_x/Zr-ZFO-3 NR photocatalyst exhibited better inactivation efficiency (99.4 %) than other metal oxide-loaded Zr-ZFO NRs (Ag₂O_x-loaded Zr-ZFO NRs (33.6 %), CuO_x-loaded Zr-ZFO NRs (77.6 %)). Additionally, the optimum CoO_x/Zr-ZFO-3 NR photocatalyst showed 98.3 % and 98.1 % degradation efficiencies for BPA and orange II dye, respectively, under visible light irradiation (λ ≥ 420 nm). Therefore, this work affords a novel, simple and rapid approach for the development of photocatalysts which active in visible light for bacterial disinfection and organic degradation.

Removal of beta-lactam antibiotic in water environment by adsorption technique using cationic surfactant functionalized nanosilica rice husk

This study aims to investigate the adsorption characteristics of cationic surfactant, cetyltrimethylamonium bromide (CTAB) onto negatively nanosilica rice husk surface and the application for antibiotic treatment in water environment. Adsorption of CTAB onto nanosilica increased with an increase of solution pH, due to an enhancement of the electrostatic attraction between cationic methylamomethylamonium groups and negatively charged nanosilica surface enhanced at higher pH. Adsorption of CTAB decreased with a decrease of ionic strength while a common intersection point (CIP) was observed for adsorption isotherm at different ionic strengths, suggesting that hydrophobic interactions between alkyl chains in CTAB molecules significantly induced adsorption and admicelles with bilayer formation were dominant than monolayer of hemimicelles. The CTAB functionalized nanosilica (CFNS) was applied for removal of beta-lactam amoxicillin (AMX). The best conditions for AMX treatment using CFNS were selected as pH 10, contact time 60 min and CFNS dosage 10 mg/mL. Removal efficiency of AMX using CFNS reached to 100% under optimum conditions while it was only 25.01% using nanosilica without CTAB. The maximum AMX adsorption capacity using CFNS of about 25 mg/g was much higher than other adsorbents. The effects of different organics such as humic acid, anionic surfactant, and other antibiotics on AMX removal using CFNS were also studied. A two-step model can fit CTAB uptake isotherms onto nanosilica and AMX onto CFNS well at different KCl concentrations. Based on the desorption of CTAB with AMX adsorption as well as adsorption isotherms, the change in surface charge and functional vibration groups after adsorption, we indicate that AMX adsorption onto CFNS was mainly controlled by electrostatic interaction. We reveal that CFNS is an excellent adsorbent for antibiotic treatment from aqueous solution.

Construction of SnO2/g-C3N4 an effective nanocomposite for photocatalytic degradation of amoxicillin and pharmaceutical effluent

The current study mainly focused on the fabrication of 2D graphitic carbon nitride-supported tin oxide nanoparticles (SnO₂/g-C₃N₄) for the effective degradation of Amoxicillin (AMX). Tin oxide (SnO₂) NPs were prepared by green and easy modification technique, and then it is decorated over g-C₃N₄ nanosheets. The structural morphology and surface composition of the synthesized SnO₂/g-C₃N₄ nanocomposite were fully analysed by UV-Vis, XRD, XPS, and HR-SEM with EDAX, FT-IR, and BET analysis. The (HR-TEM) microscopy, the size of SnO₂ NPs which as a diameter is about 6.2 nm. The Raman analysis revealed that the SnO₂/g-C₃N₄ composite had a moderate graphitic structure, with a measured I_D/I_g value of 0.79. The degradation efficiency of antibiotic pollutant AMX and pharma effluent treatment was monitored by UV spectroscopy. The optical band gap of SnO₂ (2.9 eV) and g-C₃N₄ (2.8 eV) photocatalyst was measured by Tauc plots. To investigate the mechanism through the photodegradation efficiency of the catalyst was analysed by using different Scavenger EDTA-2Na holes (h⁺) has a greater contribution towards the degradation process. Under visible irradiation, SnO₂/g-C₃N₄ nanocomposite has exhibited an excellent degradation performance of 92.1% against AMX and 90.8% for pharmaceutical effluent in 80 min.

Potential application of Fusarium fungal strains (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) for removal of Tl (I) ions from water

Water pollution caused by heavy metals poses a serious threat to the ecosystem and human health. Among the various treatment techniques for water remediation, adsorption is an efficient method due to its high capacity, low cost, and simplicity. Thallium (Tl) is highly toxic to mammals and its removal from water is gaining increasingly prominent attention. In this study, three fungal strains (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) were tested for removal of Tl (I) from aqueous solutions and showed excellent removal performance. The prepared inactive fungal strains were characterized by XRD, FT-IR, SEM, and XPS analyses. The effects of pH, contact time, biomass dosage, and reaction temperature on the removal efficiency of Tl (I) were systematically investigated. The results indicated that the adsorption isotherm data fit well with the Langmuir model, and the pseudo-second-order model was more consistent with the kinetic data description. The maximum adsorption capacity of the fungal strain (Fusarium sp. FP, Arthrinium sp. FB, and Phoma sp. FR) for Tl (I) was found to be 94.69 mg/g, 66.97 mg/g, and 52.98 mg/g, respectively. The thermodynamic data showed that the sorption process was spontaneous and endothermic. The present study showed that the inactive fungal strains could be a promising adsorbent material for Tl (I) removal.

Eco-friendly dual-edged management of fly ash and its antagonistic interplay with Meloidogyne incognita on beetroot (Beta vulgaris L.)

Fly ash (FA) management is a key concern of ecologists around the world, so its potential as a nutritional supplement for agro-ecosystems needs to be explored. Therefore, alternate techniques that are eco-friendly to manage this emerging dual-edged waste are preferable in this field. The current study sought to determine the soil-modifying, crop yield improvement, and nematicidal properties of FA. In this study, beetroot seeds were sown in pots comprising field soil amended with differing proportions of FA (w/w) revealed the bio-fold properties of FA. Biomineralization and mapping of elements revealed that increased nutritional elements in soil supplemented with 15% FA induced growth-performance and yield of beetroot. Molecularly and morphologically characterized Meloidogyne incognita was used as nematode in this study for optimization of nematicidal properties FA. Plant growth performance, photosynthetic pigments, and yield of beetroot were significantly reduced owing to M. incognita as compared to control (un-treated and un-inoculated), and 15% FA reversed the negative effect of M. incognita significantly (P _< 0.05) as compared to control plants. Confocal laser microscopy confirmed that 15% FA augmented in soil reduced nematode-juvenile invasion in beetroot as compared with control. The PCA (principal component analysis) accounted for 98.63% and 98.8% for the total-data variability in plants without nematodes and total data variability in treated plants (M. incognita + FA) respectively, which showed fit for a significant correlation between the various studied parameters in present study.

Development of siderophore based rhizobacterial consortium for the mitigation of biotic and abiotic environmental stresses in tomatoes: An in vitro and in planta approach

AIM

Tomato associated plant-growth promoting rhizosphere bacteria were screened for effective antagonistic activity against the fungal vascular wilt pathogens; tolerance to heavy metals; and enhancing the bioavailability of iron for tomato plants through in vitro and in vivo approaches.

METHODS AND RESULTS

Among the 121 rhizobacteria screened for siderophores, 25 isolates were observed to be siderophore producers and out of these, seven isolates chelate copper and iron thus exhibiting in vitro antagonism against the virulent strains of Fusarium oxysporum f. sp. lycopersici MTCC10270 (Fol), Fusarium equiseti MFol, and Sarocladium sp. SWL isolated from infected tomatoes. Pseudomonas stutzeri KRP8 was identified to be the most potent strain among the siderophore producers and its siderophores were chemically characterized by mass spectra as metal bound and metal-free forms. Upon bio-inoculation of fortified bacterial consortium (siderozote) into the rhizosphere of vermiculite pot cultured tomatoes supplied with varying concentrations of iron and copper ions, we observed in planta growth improvements, antagonism, enhancement of bioavailability of iron and heavy metal tolerance using Inductively Coupled Plasma-Optical Emission Spectrometry.

CONCLUSION AND SIGNIFICANCE OF THE STUDY

Our rhizobacterial consortium provides an opportunity for soil reclamation through an ecofriendly method for a heavy metal-free agricultural landscape.

Novel g-C3N4/Cu-doped ZrO2 hybrid heterostructures for efficient photocatalytic Cr(VI) photoreduction and electrochemical energy storage applications

Pure ZrO₂, graphitic carbon nitride, Cu-doped ZrO₂ nanoparticles (Cu-Zr), and doped Cu-Zr nanoparticles decorated on the g-C₃N₄ surface (g-CuZr nanohybrids) were successfully prepared by a hydrothermal technique. Synthesized catalysts were examined by XRD, FE-SEM, TEM, UV-Vis spectroscopy, photoluminescence (PL), and BET surface measurements, respectively. The photocatalytic reduction of Cr(VI) photoreduction as well as energy storage supercapacitor applications were thoroughly investigated. The g-CuZr hybrid photocatalyst outperformed other pristine photocatalysts in terms of light absorption and catalytic Cr(VI) reduction performance under stimulated solar light irradiation. Furthermore, methylene blue (MB) was used as a photosensitizer to further improve the Cr(VI) photoreduction performance. In precise, the heterostructured hybrid catalyst exhibited improved photocatalytic Cr(VI) photoreduction activity (∼88.1%) in 5 mg/L MB solution over other catalysts. Moreover, the decoration of Cu-Zr on the surface of g-C₃N₄ enhanced the absorption ability of light and catalytic Cr(VI) photoreduction performance. The PL, EIS, and transient photocurrent analysis demonstrated that the efficiency of the charge carrier's separation in the nanohybrid catalyst was superior over other catalysts. Furthermore, heterostructured g-CuZr nanohybrid electrode exhibited superior specific capacitance (297.2 F/g) over other electrodes, which are 5.5 folds (54.01 F/g), ∼2 folds (144.01 F/g) better than pure ZrO₂ and g-C₃N₄ electrodes. Likewise, the nanohybrid electrode retained about 90% of the capacitive value after 2500 cycles over its initial capacitance.

Isolation of functional bacterial strains from chromium-contaminated site and bioremediation potentials

In this study, two Cr(VI)-reducing functional bacterial strains (TJ-1 and TJ-5) were successfully isolated and screened from the chromium-contaminated soil from a real site. The 16S rRNA gene sequences were analysed, which showed high similarity (>99%) with Stenotrophomonas maltophilia (TJ-1) and Brucella intermedius (TJ-5) species. The optimum growth for the two bacteria to reduce Cr(VI) were achieved at pH 7.0 and initial inoculation amount of 5%. The two strains were applied to real contaminated soil samples and showed better Cr removal when external carbon sources were added. Using sawdust as a solid-phase carbon source supplement, both TJ-1 and TJ-5 showed higher remediation efficiency (99.77% and 93.86%) than using glucose as the carbon source (68.56% and 70.87%). Results of the stability of soil Cr(VI) bioremediation revealed that the water-soluble Cr(VI) content of bioremediated sample remained unchanged, indicating that Cr(VI) is not easily released after death of the strains. Solid-phase carbon source supplements may help the cells to attach and grow into biofilms, creating a better growth condition which improved the remediation efficiency. Column experiments showed that the total remediation efficiencies by the two strains were 34.23% and 20.63%, respectively, within a short time period (76 h). Therefore, the two strains showed great bioremediation potentials for chromium-contaminated sites and can be used in future application of in-situ bioremediation.

Investigation of the adsorptive removal of methylene blue using modified nanocellulose

In this study, Ethylenediamine tetraacetic acid (EDTA) embedded nanocellulose (NCED) has been used to study the adsorptive removal of methylene blue (MB) from simulated wastewater. The morphological characterizations have been checked with FESEM, FETEM, AFM, and BET pore analysis, while the fingerprinting of the material has been analyzed with the help of FTIR, Raman spectroscopy, EDS, XRD and TGA. For the experimental designing involving four parameters that affect the removal efficiency of MB, the layout has been prepared with the help of Central Composite Design (CCD). For the correlation among the parameters and their subsequent impact on the removal percentage, response surface methodology (RSM) has been employed. Maximum removal percentage of MB using NCED was found out to be 91.14%. The adsorption process was found to be good fit with the Langmuir isotherm and Elovich kinetics model. From the thermodynamics study, the spontaneity and the endothermic nature of the process was confirmed. With the help of all the obtained data and the associated removal efficiency, NCED could play a role of cost-effective and eco-friendly alternative to the expensive methods of toxic dye removal from wastewater.

One-Step Fabrication of Amino-Functionalized Fe3O4@SiO2 Core-Shell Magnetic Nanoparticles as a Potential Novel Platform for Removal of Cadmium (II) from Aqueous Solution

Fe3O4@SiO2-NH2 core-shell magnetic nanoparticles were developed by a rapid one-step precipitation route followed by reverse microemulsion and amine functionalization. In this study, an Fe3O4@SiO2-NH2 nanoparticle was used to evaluate its adsorption efficiency for the treatment of a synthetic solution of Cd(II) ion. The structural and physicochemical properties of Fe3O4@SiO2-NH2 nanoparticles were characterized by XRD, SEM-EDAX, TEM, FTIR and TGA. From the TEM analysis, the morphology of Fe3O4@SiO2-NH2 was found as 100–300 nm. In TGA, the first weight loss was noticed between 373 and 573 K, the second was between 673 and 773 K and the final weight loss took place above 773 K. Batch experimental tests, such as pH, dosage of Fe3O4@SiO2-NH2, Cd(II) ion concentration, temperature as well as interaction time, were conducted and evaluated. Experimental study data were used for the non-linear forms exhibited by isotherms and kinetics of the sorption procedure. The equilibrium adsorption observations were adequately combined with pseudo-first-order kinetics as well as Freundlich isotherm. Monolayer maximum adsorption capacity was found to be 40.02 mg/g, recorded at pH 6 with an interaction time of 30 min, temperature of 303 K and sorbent dose of 2.0 g/L. The thermodynamic study indicated that the adsorption process was an exothermic, spontaneous reaction (−∆oo = −15.46–7.81 (kJ/mol)). The as-synthesized sorbent had excellent recyclability, and its adsorption efficiency was maintained after five cycles of reuse. The findings of the study exhibited the magnetic Fe3O4@SiO2-NH2-nanoparticle as an alternative effective adsorbent in eradicating Cd(II) ions from aqueous solution.

Activated multi-walled carbon nanotubes decorated with zero valent nickel nanoparticles for arsenic, cadmium and lead adsorption from wastewater in a batch and continuous flow modes

Nickel nanoparticles (NiNPs) supported on activated multi-walled carbon nanotubes (MWCNTs) were used as an adsorbent applied towards Pb(II), As(V) and Cd(II) remediation from industrial wastewater. The result revealed the hydrophilic surface of MWCNTs-KOH was enhanced with the incorporation of NiNPs enabling higher surface area, functional groups and pore distribution. Comparatively, the removal of Pb(II), As(V) and Cd(II) on the various adsorbents was reported as NiNPs (58.6 ± 4.1, 46.8 ± 3.7 and 40.5 ± 2.5%), MWCNTs-KOH (68.4 ± 5.0, 65.5 ± 4.2 and 50.7 ± 3.4%) and MWCNTs-KOH@NiNPs (91.2 ± 8.7, 88.5 ± 6.5 and 80.6 ± 5.8%). Using MWCNTs-KOH@NiNPs, the maximum adsorption capacities of 481.0, 440.9 and 415.8 mg/g were obtained for Pb(II), As(V) and Cd(II), respectively. The experimental data were best suited to the Langmuir isotherm and pseudo-second order kinetic model. The fitness of experimental data to the kinetic models in a fixed-bed showed better fitness to Thomas model. The mechanism of metal ion adsorption onto MWCNTs-KOH@NiNPs show a proposed electrostatic attraction, surface adsorption, ion exchange, and pore diffusion due to the incorporated NiNPs. The nanocomposite was highly efficient for 8 adsorption cycles. The results of this study indicate that the synthesized nanocomposite is highly active with capacity for extended use in wastewater treatment.

Algae biotechnology for industrial wastewater treatment, bioenergy production, and high-value bioproducts

A growing world population is causing hazardous compounds to form at an increasingly rapid rate, calling for ecological action. Wastewater management and treatment is an expensive process that requires appropriate integration technology to make it more feasible and cost-effective. Algae are of great interest as potential feedstocks for various applications, including environmental sustainability, biofuel production, and the manufacture of high-value bioproducts. Bioremediation with microalgae is a potential approach to reduce wastewater pollution. The need for effective nutrient recovery, greenhouse gas reduction, wastewater treatment, and biomass reuse has led to a wide interest in the use of microalgae for wastewater treatment. Furthermore, algae biomass can be used to produce bioenergy and high-value bioproducts. The use of microalgae as medicine (production of bioactive and medicinal compounds), biofuels, biofertilizers, and food additives has been explored by researchers around the world. Technological and economic barriers currently prevent the commercial use of algae, and optimal downstream processes are needed to reduce production costs. Therefore, the simultaneous use of microalgae for wastewater treatment and biofuel production could be an economical approach to address these issues. This article provides an overview of algae and their application in bioremediation, bioenergy production, and bioactive compound production. It also highlights the current problems and opportunities in the algae-based sector, which has recently become quite promising.

The photocatalytic performance and mechanism of magnetically retrievable Z-scheme Cr2O3–Fe3O4/C hetero-nanostructure polyhedra

Magnetically retrievable Cr2O3–Fe3O4/C hetero-nanostructure polyhedra have been fabricated. The formation of Z-scheme Cr2O3–Fe3O4/C obviously improves the visible light absorption and promotes the separation of photogenerated charge carriers.

Highly efficient scavenging of Cr(VI) by two-dimensional titanium carbide nanosheets: kinetics, isotherms and thermodynamics analysis

In this study, two-dimensional (2D) MXene material (Ti₃C₂T_x) was employed to investigate its potentials toward the Cr(VI) removal in aqueous system by batch experiments. Characterization techniques such as SEM-EDS, HRTEM, XRD, FI-TR and XPS were used to analyze the structure and interaction of Ti₃C₂T_x before and after Cr(VI) adsorption. The results indicated that the layered structure of Ti₃C₂T_x had unique surface functional properties and abundant active sites, such as -OH, Ti-O, C = O, which exhibited high adsorption capacity for Cr(VI) removal. The Cr(VI) adsorption capacity by Ti₃C₂T_x decreased with the increase of pH, and its maximum value can reach 169.8 mg/g at pH = 2.0. The adsorption kinetic was well-explained by a pseudo-second-order kinetic, indicating that chemical interaction played a dominant role in the adsorption of Cr(VI) on Ti₃C₂T_x. Meanwhile, the isotherm data was calculated to conform to the Freundlich isotherm model. Thermodynamic analysis indicated that the adsorption process of Cr(VI) on Ti₃C₂T_x was a spontaneous endothermic process. These experimental results revealed that Ti₃C₂T_x had tremendous potential in heavy metals adsorption from aqueous solutions.

Mixed biosorbent of agro waste and bacterial biomass for the separation of Pb(II) ions from water system

Adsorption of Pb(II) ions in aqueous systems by newly developed mixed biomass has been explored. Mixed biomass was prepared from agro-waste (raw Banyan tree bark, RBTB) and bacterial biomass (Pannonibacter phragmitetus). Chemical modification by sulphuric acid treatment of raw banyan tree bark (SMBTB) was accomplished for the effective separation of toxic Pb(II) ions from the aquatic system. FTIR, SEM and EDX analysis was utilized to deduce sorption characteristics of mixed biomass. Pb(II) ions maximal removal has occurred at pH-6.0, lead (II) ions concentration-25 mg/L, time and mixed biomass dosage (60 min and 3.5 g/L for RBTB - Pannonibacter phragmitetus; 30 min and 1.5 g/L for SMBTB - Pannonibacter phragmitetus) and temperature (30 °C). Data from equilibrium isotherm and kinetic analysis was best suited to the Langmuir model and pseudo-first-order kinetics. The spontaneous and exothermic nature of Pb(II) ions removal was described by thermodynamic parameters. The mixed biomass proved to be an effective and potential mixed biosorbent for toxic lead removal from solutions.

Hydroxyapatite biomaterial production from chicken (femur and beak) and fishbone waste through a chemical less method for Cd2+ removal from shipbuilding wastewater

Hydroxyapatite (HAp) powder was produced from chicken (femur and beak) and fishbone wastes and used as a green adsorbent to decrease Cd²⁺ from aqueous media. The HAp powder was generated at 900 °C and characterized using physicochemical techniques. Chicken femur' HAp (16.72 m²/g) had a higher surface compared to chicken beak and fishbone ones. The solution pH was the most important parameter in removing Cd²⁺. The highest Cd²⁺ removal was achieved at pH 6, temperature of 25 °C, contact time of 80 min, and adsorbent mass of 2 g/L. The Cd²⁺ adsorption data fitted well with the quasi-second-order model in kinetics and the Freundlich model in isotherm. The highest adsorption capacity of Cd²⁺ using HAp-chicken femur, HAp-fish bone, and HAp-chicken beak was determined 22.94 mg/g, 21.54 mg/g, and 21.45 mg/g, respectively. The Cd²⁺ adsorption using HAp powder was a spontaneous and exothermic process and accidental collisions at the liquid-solid interface were reduced. The decrease of Cd²⁺ adsorption efficiency was not significant after multiple recovery steps of the desired powders. In addition to Cd²⁺, other parameters of real wastewater (shipbuilding industry) were reduced by the proposed adsorbents. The utilization of hydroxyapatite powder is expected to be a cheap and eco-friendly method for eliminating metals such as Cd²⁺.

Sorbent-based devices for the removal of spilled oil from water: a review

Always, oil spills do cause serious and dire consequences for the environment, nature, and society that it consumes much time and socio-economic resources to overcome such consequences. Oil spills, hence, posed a big challenge in searching the advanced technologies and devices to recover spilled oil rapidly and efficiently. Indeed, sorbents have been found to play an extremely critical role in the spilled-oil remediation processes. Recently, a large number of various advanced sorbents and sorbent-based oil-collecting devices/technologies have been developed to enhance the oil-recovery capacity. Therefore, it is necessary to have a comprehensive assessment of the application of sorbent-based oil-collecting devices/technologies in recovering spilled oil. Due to this reason, this paper aims to provide a comprehensive review of the advanced technologies of the combination of sorbents and oil-collecting devices in the oil cleanup strategies. Two main oil-collecting devices such as booms and skimmers that could conjunct with sorbents were critically evaluated on the basis of the applicability and technological features, indicating that the capacity of oil spill recovery could achieve 90%. Moreover, oil-storage and oil-collecting devices were also completely mentioned. Last but not least, technical directions, concerns over the application of sorbents in oil recovery, and existing challenges relating to storage, transport, and disposal of used sorbents were discussed in detail. In the future, the automatic process of spilled oil recovery with the conjunction between advanced devices and environmentally friendly high-efficiency sorbents should be further investigated to minimize the environmental impacts, reduce the cost, as well as maximize the collected oil spill.

A review on algal-bacterial symbiotic system for effective treatment of wastewater

Industrialization, urbanization and other anthropogenic activities releases different organic and inorganic toxic chemicals into the environment which prompted the water contamination in the environment. Different physical and chemical techniques have been employed to treat the contaminated wastewater, among them biological wastewater treatment using algae has been studied extensively to overwhelm the constraints related to the usually utilized wastewater treatment techniques. The presence of bacterial biota in the wastewater will form a bond with algae and act as a natural water purification system. The removal efficiency of single algae systems was very low in contrast with that of algal-bacterial systems. Heterotrophic microorganisms separate natural organic matter that is discharged by algae as dissolved organic carbon (DOC) and discharges CO₂ that the algae can take up for photosynthesis. Algae bacteria associations offer an exquisite answer for tertiary and scrape medicines because of the capacity of micro-algae to exploit inorganic compounds for their development. Furthermore, for their ability to evacuate noxious contaminants, in this way, it does not prompt optional contamination. The present review contribute the outline of algae-bacteria symbiotic relationship and their applications in the wastewater treatment. The role of algae and bacteria in the wastewater treatment have been elucidated in this review. Moreover, the efforts have been imparted the importance of alage-bacteria consortium and its applications for various pollutant removal from the environment.

Biologically reduced graphene oxide as a green and easily available photocatalyst for degradation of organic dyes

The disposal of untreated textile industrial wastewater having unmanageable pollutants is a global issue. Eco-friendly remediation technology is needed for the removal of environmental contaminants. In this study, a simple hydrothermal method is adapted to synthesis reduced graphene oxide (PErGO) using Phyllanthus emblica fruits extract and used as a photocatalyst for the degradation of synthetic toxic dyes. The physicochemical properties of green synthesized PErGO are confirmed using UV-Vis spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction. The I_D/I_G ratio is found as 1.02 for GO which is improved to 1.15 for PErGO, which confirms the existence of unrepaired defects after the elimination of negatively charged O₂ moieties from the surface of GO. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis show well-exploited PErGO morphology. The photocatalytic removal of methylene blue (MB) and methyl orange (MO) dyes is confirmed using UV-vis spectrophotometer. PErGO shows about 92% of MO and 91% of MB degradation within 90 min of sunlight exposure while carried out as a mixed dye degradation. The sustainability of this catalyst is confirmed by testing it for five subsequent degradation cycles and noticed a stable and significant degradation activity. Outcomes from this study suggest that eco-friendly PErGO can be used as an alternate sustainable material to treat a large volume of wastewater from various dye industries.

Facile Synthesis of Polyethylene Glycol@Tannin-Amine Microsphere towards Cr(VI) Removal

Herein, a synthetic strategy for a rough microsphere Cr(VI)-adsorbent via the reaction of tannic acid (TA) and 1,6-hexanediamine (HA) and using polyethylene glycol (PEG) as surface modifier was presented. This adsorbent was characterized by a Fourier Transform Infrared spectrometer (FTIR), thermogravimetic analysis (TGA), X-ray photoelectron spectroscopy (XPS), etc. Certain factors, including contact time, PEG@poly(tannin-1,6-hexanediamine) (PEG@PTHA) dosage, initial concentration, and experimental temperature affecting the Cr(VI) adsorption performance of adsorbent were explored. PEG@PTHA can adsorb Cr and the Cr(VI) was reduced up to Cr(III) due to the existence of phenolic hydroxyl groups. Its adsorption capacity can reach up to 300 mg/g within 10 min and approximately 100% removal percentage below the initial concentration of 100 mg/L. Its behavior matched well with the Langmuir isotherm model and pseudo-second-order kinetic model. A PEG@PTHA adsorbent with maximum adsorption capacity (450 mg/g) has great prospects in Cr(VI)-sewage treatment.

Innovative Magnetite Based Polymeric Nanocomposite for Simultaneous Removal of Methyl Orange and Hexavalent Chromium from Water

One of the most important directions for environmental remediation is the effective removal of dyes and toxic heavy metals from water using newly fabricated nanoadsorbents. Here, magnetic Fe3O4 nanoparticles were combined with nitrogen-containing functional group polymers chitosan (CS) and polypyrrole (ppy) to synthesize a nanocomposite (polypyrrole@magnetic chitosan) useful for removing methyl orange (MO) and hexavalent chromium (Cr (VI)) from water. The physicochemical properties of the nanocomposite were determined using SEM, TEM, XRD, FT–IR, and TGA techniques. The effect of different factors on the adsorption system was studied including the contact time, pH, and the effect of co-existed ions. The kinetic study illustrated that the adsorption fit well with Langmuir isotherm. The maximum adsorption capacity of MO and Cr (VI) was found to be 95 and 105 mg/g, respectively. The reusability of the nanocomposite was studied for up to five cycles using 0.1 M NaOH as eluent with a slight decrease of adsorbent efficiency. Furthermore, the removal mechanism studied suggested the removal of MO via adsorption and Cr (VI) via chemical reduction and adsorption. This study suggests that a ppy@magnetic chitosan nanocomposite is a promising nanoadsorbent for removing MO and Cr (VI) from water.