Coal fly ash supported CoFe2O4 nanocomposites: Synergetic Fenton-like and photocatalytic degradation of methylene blue.

Rapid industrialization is causing a serious threat for the environment. Therefore, this research was aimed in developing ceramic cobalt ferrite (CoFe2O4) nanocomposite photocatalyst coated with coal fly ash (CFA-CoFe2O4) using facile hydrothermal synthesis route and their applications against methylene blue. The pristine cobalt ferrite photocatalyst was also prepared, characterized, and applied for efficiency comparison. Prepared photocatalyst were characterized by X-ray diffraction (XRD), fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Optical response of catalysts was check using photoluminescence spectroscopy (PL). pH drift method was used for the surface charge characteristics of the material under acidic and basic conditions of solution pH. The photocatalytic degradation potential of all the materials were determined under ultra-violet irradiations. The influencing reaction parameters like pH, catalyst dose, oxidant dose, dye concentration, and irradiation time, were sequentially optimized to obtain best suited conditions. The 99% degradation of 10 ppm methylene blue was achieved within 60 min of reaction time under pH = 5 and 7, catalyst dose = 10 and 12 mg/100 mL, oxidant = 12 mM and 5 mM for cobalt ferrite and CFA-CoFe2O4 photocatalysts, respectively. Afterwards, the radical scavenging experiments were conducted to find out the effective radical scavengers (˙OH, h+, and e-) in photocatalytic degradation process. The kinetic study of the process was done by applying 1st order, 2nd order, and BMG models. Statistical assessment of interaction effect among experimental variables was achieved using response surface methodology (RSM).

Microwave Irradiation and Glutamic Acid-Assisted Phytotreatment of Tannery and Surgical Industrial Wastewater by Sorghum.

We investigated how different doses of microwave irradiation (MR) affect seed germination in Sorghum, including the level of remediation against textile and surgical wastewater (WW) by modulating biochemical and morpho-physiological mechanisms under glutamic acid (GA) application. The experiment was conducted to determine the impact of foliar-applied GA on Sorghum under wastewater conditions. Plants were treated with or without microwave irradiation (30 s, 2.45 GHz), GA (5 and 10 mM), and wastewater (0, 25, 50, and 100). Growth and photosynthetic pigments were significantly decreased in plants only treated with various concentrations of WW. GA significantly improved the plant growth characteristics both in MR-treated and -untreated plants compared with respective controls. HMs stress increased electrolyte leakage (EL), hydrogen peroxide (H2O2), and malondialdehyde (MDA) content; however, the GA chelation significantly improved the antioxidant enzymes activities such as ascorbate oxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) both in MR-treated and -untreated plants under WW stress compared with respective controls. The results suggested that the MR-treated plants accumulate higher levels of HMs under GA addition in comparison to the WW-only-treated and MR-untreated plants. The maximum increase in Cd accumulation was observed in the range of 14-629% in the roots, 15-2964% in the stems, and 26-4020% in the leaves; the accumulation of Cu was 18-2757% in the roots, 15-4506% in the stems, and 23-4605% in the leaves; and the accumulation of Pb was 13-4122% in the roots, 21-3588% in the stems, and 21-4990% in the leaves under 10 mM GA and MR-treated plants. These findings confirmed that MR-treated sorghum plants had a higher capacity for HMs uptake under GA and could be used as a potential candidate for wastewater treatment.

Mixed metal ferrite (Mn0.6Zn0.4Fe2O4) intercalated g-C3N4nanocomposite: efficient sunlight driven photocatalyst for methylene blue degradation.

Visible active mixed metal ferrite intercalated semiconductor photocatalyst Mn0.6Zn0.4Fe2O4/g-C3N4was prepared via facile hydrothermal and liquid assembly method for methylene blue (MB) dye degradation. The prepared samples were well characterized in term of their functional groups, crystallinity, elemental analysis, surface morphology using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, energy dispersive x-ray, and scanning electron microscopy, respectively. The optical response of catalysts was checked by estimating the energy band gap (Eg) of semiconductor photocatalysts using UV-vis spectroscopy. The photoluminescence spectroscopy was also performed to estimate the reduction in emission intensity after insertion of g-C3N4into Mn0.6Zn0.4Fe2O4.The novel composition of Mn0.6Zn0.4Fe2O4with g-C3N4,improved the optical response of pristine photocatalysts due to the reduction in the energy band gap and insertion of heterojunction. The surface area analysis of Mn0.6Zn0.4Fe2O4and Mn0.6Zn0.4Fe2O4/g-C3N4were acquired by Brunauer-Emmett-Teller. Point zero charge was also determined to observe the surface behavior of composite under different solution pH. Various parameters such as pH, catalyst dose, oxidant dose, irradiation time and initial dye concentration were optimized, and their effects were studied in photo-Fenton process. It was observed that 98% MB dye was degraded under optimized conditions (pH = 8, composite dose = 50 mg/100 ml, oxidant dose = 7 mM, initial dye conc. = 10 ppm, and irradiation time = 120 min). The results showed that when the ferrites of mixed metals (Mn, Zn) were used with g-C3N4their photocatalytic activity enhanced due to mutual effect of both mixed metals ferrite and g-C3N4, which is considerably higher than their individual effect already reported. Furthermore, the combined effect of independent variables was evaluated by response surface methodology.

Degradation of acetamiprid using graphene-oxide-based metal (Mn and Ni) ferrites as Fenton-like photocatalysts.

This study aims to explore the photocatalytic potential of graphene-oxide-based metal ferrites for the degradation of acetamiprid (an odorless neonicotinoid pesticide). Metal (Mn and Ni) ferrites (along with their graphene oxide composites) were prepared by the hydrothermal method while graphene oxide (GO) was synthesized using a modified Hummer's method. The composites were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The photocatalysts were studied for their Fenton-like advanced oxidation process to degrade acetamiprid. The composites showed excellent activity against acetamiprid degradation (>90%) in 60 min under UV irradiation. The detailed optimization study was carried out to investigate the influential variables (such as pH, catalyst dose, pollutant concentration, irradiation time, oxidant dose, etc.) to achieve enhanced degradation efficiency. Moreover, the findings were endorsed by central composite design (CCD). It was concluded that degradation was enhanced in an appropriate combination of photocatalyst and hydrogen peroxide. The magnetic character of the metal ferrites and their composites played an important role in the easy separation and reusability of these materials. The present findings result in highly effective, easy to handle and stable heterogeneous photo-Fenton materials for wastewater remediation.

Magnetic Hierarchically Macroporous Emulsion-Templated Poly(acrylic acid)-Iron Oxide Nanocomposite Beads for Water Remediation.

Tainting of waterbodies with noxious industrial waste is the gravest environmental concern of the day that continues to wreak inevitable havoc on human health. To cleanup these hard-to-remove life-threatening water contaminants, we have prepared hierarchically porous poly(acrylic acid) beads by emulsion templating. These emulsion-templated macroporous polymer beads not only mediate the synthesis of Fe3O4 nanoparticles inside their porous network using a coprecipitation approach but, in turn, create diverse anchoring sites to immobilize an additional poly(acrylic acid) active layer onto the nanocomposite beads. These post-synthetically modified nanocomposite beads with macropores and abundant acrylic acid moieties offer the ready mass transfer and fair advantage of relatively higher overall negative charge to efficiently adsorb lead [Pb(II)] and crystal violet with impressive performance-even superior to many of the materials explored in this regard so far. Furthermore, the strong entanglement of nanoparticles in the porous polymeric scaffolds tackles the curb of trade-off between all-round effective remediation and secondary pollution and the millimeter size eases their processing and recovery during the adsorption tests, thereby making these materials practically worthwhile.

Carbon dioxide-activated mesoporous date palm fronds carbon integrated with MnO2/polyaniline for highly efficient capacitive deionization of water.

The continuous population growth and drying up the freshwater reservoirs around the world are increasing the demand for fresh water. Therefore, there is an urgent need to explore newer technologies able to purify water on large scales for human usage. Capacitive deionization is one of the most promising approaches to generate fresh water by the removal of salt ions from brackish water. In this work, we prepared three different capacitive deionization electrodes using carbonized palm tree fronds (PFC). These PFC activation was achieved using CO2 at 900°C. To generate the deionization electrodes, PFC activated carbon was combined with either polyaniline (PANI), MnO2, or both (PFC-PANI, PFC-MnO2, and PFC-MnO2-PANI). The MnO2 and PANI provided additional functionality and enhanced electrical conductivity, which resulted in much higher Na+ and Cl- ions adsorption. The BET surface area of PFC-MnO2-PANI was estimated to be 208.56 m2/g, which is approximately three times that of PCF-PANI and PFC-MnO2 alone. The morphological analysis showed that the PANI and MnO2 nanorods were well dispersed throughout the PFC network. Although PANI and MnO2 is largely embedded inside the PFC network, some remnants are visible on the surface of the electrodes. The cyclic voltammetry (CV) curves showed capacitive behavior of all electrodes in which PFC-MnO2-PANI showed highest specific capacitance of 84 F/g, while the PFC-MnO2 and PFC-PANI showed 42 and 43 F/g, respectively. Owing to its enhanced functionality and CV characteristics, the PFC-MnO2-PANI showed maximum salt adsorption capacity of 10.5 mg/g in contrast to 3.72 and 5.64 mg/g for PFC-MnO2 and PFC-PANI, respectively. Moreover, the measured contact angle for PFC-MnO2-PANI was ~51°, which indicates the hydrophilic nature of electrode that improved ions adsorption. PRACTITIONER POINTS: Date tree fronds were converted into mesopores carbon using CO2 as activation agent. Three composites were prepared with PANI, MnO2, and date palm fronds activated carbon (PFC-MnO2, PFC-MnO2-PANI, and PFC-PANI). Surface area, pore profile, surface morphology, electrochemical behavior, desalination performance, and hydrophilicity of all the electrodes were investigated. The PFC-MnO2-PANI showed maximum salt adsorption capacity of 10.5 mg/g in contrast to 3.72 and 5.64 mg/g for PFC-MnO2 and PFC-PANI, respectively.

Enhancing the Photocatalytic Degradation of Methylene Blue with Graphene Oxide-Encapsulated g-C3N4/ZnO Ternary Composites.

Methylene blue (MB) is a toxic contaminant present in wastewater. Here, we prepared various composites of graphene oxide (GO) with graphitic carbon nitride (g-C3N4) and zinc oxide (ZnO) for the degradation of MB. In comparison to ZnO (22.9%) and g-C3N4/ZnO (76.0%), the ternary composites of GO/g-C3N4/ZnO showed 90% photocatalytic degradation of MB under a light source after 60 min. The experimental setup and parameters were varied to examine the process and effectiveness of MB degradation. Based on the results of the experiments, a proposed photocatalytic degradation process that explains the roles of GO, ZnO, and g-C3N4 in improving the photocatalytic efficacy of newly prepared GO/g-C3N4/ZnO was explored. Notably, the g-C3N4/ZnO nanocomposite's surface was uniformly covered with ZnO nanorods. The images of the samples clearly demonstrated the porous nature of GO/g-C3N4/ZnO photocatalysts, and even after being mixed with GO, the g-C3N4/ZnO composite retained the layered structure of the original material. The catalyst's porous structure plausibly enhanced the degradation of the contaminants. The high-clarity production of g-C3N4 and the effectiveness of the synthesis protocol were later validated by the absence of any trace contamination in the energy-dispersive X-ray spectroscopy (EDS) results. The composition of the ZnO elements and their spectra were revealed by the EDS results of the prepared ZnO nanorods, g-C3N4/ZnO, and GO/g-C3N4/ZnO. The outcomes indicated that the nanocomposites were highly uncontaminated and contained all necessary elements to facilitate the transformative process. The results of this experiment could be applied at a large scale, thus proving the effectiveness of photocatalysts for the removal of dyes.

Semiconductor Nanomaterial Photocatalysts for Water-Splitting Hydrogen Production: The Holy Grail of Converting Solar Energy to Fuel.

Nanomaterials have attracted attention for application in photocatalytic hydrogen production because of their beneficial properties such as high specific surface area, attractive morphology, and high light absorption. Furthermore, hydrogen is a clean and green source of energy that may help to resolve the existing energy crisis and increasing environmental pollution caused by the consumption of fossil fuels. Among various hydrogen production methods, photocatalytic water splitting is most significant because it utilizes solar light, a freely available energy source throughout the world, activated via semiconductor nanomaterial catalysts. Various types of photocatalysts are developed for this purpose, including carbon-based and transition-metal-based photocatalysts, and each has its advantages and disadvantages. The present review highlights the basic principle of water splitting and various techniques such as the thermochemical process, electrocatalytic process, and direct solar water splitting to enhance hydrogen production. Moreover, modification strategies such as band gap engineering, semiconductor alloys, and multiphoton photocatalysts have been reviewed. Furthermore, the Z- and S-schemes of heterojunction photocatalysts for water splitting were also reviewed. Ultimately, the strategies for developing efficient, practical, highly efficient, and novel visible-light-harvesting photocatalysts will be discussed, in addition to the challenges that are involved. This review can provide researchers with a reference for the current state of affairs, and may motivate them to develop new materials for hydrogen generation.

A critical review in recent progress of hollow fiber membrane contactors for efficient CO2 separations.

Among wide range of membrane-based operations, membrane contactors, as they reify comparatively modern membrane-based mechanism are gaining quite an attention in both pilot and industrial scales. In recent literature, carbon capture is one of the most researched applications of membrane contactors. Membrane contactors have the potential to minimize the energy consumption and capital cost of traditional CO2 absorptions columns. In a membrane contactor, CO2 regeneration can take place below the solvent boiling point, resulting into lower consumption of energy. Various polymeric as well as ceramic membrane materials have been employed in gas liquid membrane contactors along with several solvents including amino acids, ammonia, amines etc. This review article provides detailed introduction of membrane contactors in terms of CO2 removal. It also discusses that the main challenge that is faced by membrane contactors is membrane pore wetting caused by solvent that in turn can reduce the mass transfer coefficient. Other potential challenges such as selection of suitable solvent and membrane pair as well as fouling are also discussed in this review and are followed by potential ways to reduce them. Furthermore, both membrane gas separation and membrane contactor technologies are analysed and compared in this study on the basis of their characteristics, CO2 separation performances and techno economical transvaluation. Consequently, this review provides an opportunity to thoroughly understand the working principle of membrane contactors along its comparison with membrane-based gas separation technology. It also provides a clear understanding of latest innovations in membrane contactor module designs as well as challenges encountered by membrane contactors along with possible solutions to overcome these challenges. Finally, semi commercial and commercial implementation of membrane contactors has been highlighted.

MoS2-Cu/CuO@graphene Heterogeneous Photocatalysis for Enhanced Photocatalytic Degradation of MB from Water.

The industrial revolution resulted in the contamination of natural water resources. Therefore, it is necessary to save and recover the natural water resources. In this regard, polymer-based composites have attracted the scientific community for their application in wastewater treatment. Herein, molybdenum disulfide composites with a mix phase of copper, copper oxide and graphene (MoS2-Cu/CuO@GN) were synthesized through the hydrothermal method. Methylene blue (MB) was degraded by around 93.8% within the 30 min in the presence of MoS2-Cu/CuO@GN under visible light. The degradation efficiency was further enhanced to 98.5% with the addition of H2O2 as a catalyst. The photocatalytic degradation efficiency of pure MoS2, MoS2-Cu/CuO and MoS2-Cu/CuO@GN were also investigated under the same experimental conditions. The structural analysis endorses the presence of the Cu/CuO dual phase in MoS2. The charge recombination ratio and band gap of MoS2-Cu/CuO@GN were also investigated in comparison to pure MoS2 and MoS2-Cu/CuO. The chemical states, the analysis of C1s, O1s, Mo3d and Cu2p3, were also analyzed to explore the possible interaction among the present elements. The surface morphology confirms the existence of Cu/CuO and GN to MoS2.

Freestanding Activated Carbon Nanocomposite Electrodes for Capacitive Deionization of Water.

Freshwater reserves are being polluted every day due to the industrial revolution. Man-made activities have adverse effects upon the ecosystem. It is thus the hour of need to explore newer technologies to save and purify water for the growing human population. Capacitive deionization (CDI) is being considered as an emerging technique for removal of excess ions to produce potable water including desalination. Herein, cost-effective activated carbon incorporated with carbon nanotubes (CNT) was used as a freestanding electrode. Further, the desalination efficiency of the designed electrodes was tuned by varying binder concentration, i.e., polyvinylidene difluoride (PVDF) in the activated carbon powder and CNT mixture. PVDF concentration of 5, 7.5, 10, and 12.5 wt% was selected to optimize the freestanding electrode formation and further applied for desalination of water. PVDF content affected the surface morphology, specific surface area, and functional groups of the freestanding electrodes. Moreover, the electrical conductivity and specific surface area changed with PVDF concentration, which ultimately affected the desalination capacity using the freestanding electrodes. This study paves the way to produce cost effective carbon-based freestanding electrodes for capacitive deionization and other applications including battery electrodes.

Development and Mechanistic Studies of Ternary Nanocomposites for Hydrogen Production from Water Splitting to Yield Sustainable/Green Energy and Environmental Remediation.

Photocatalysts lead vitally to water purifications and decarbonise environment each by wastewater treatment and hydrogen (H2) production as a renewable energy source from water-photolysis. This work deals with the photocatalytic degradation of ciprofloxacin (CIP) and H2 production by novel silver-nanoparticle (AgNPs) based ternary-nanocomposites of thiolated reduce-graphene oxide graphitic carbon nitride (AgNPs-S-rGO2%@g-C3N4) material. Herein, the optimised balanced ratio of thiolated reduce-graphene oxide in prepared ternary-nanocomposites played matchlessly to enhance activity by increasing the charge carriers' movements via slowing down charge-recombination ratios. Reduced graphene oxide (rGO), >2 wt.% or <2 wt.%, rendered H2 production by light-shielding effect. As a result, CIP degradation was enhanced to 95.90% by AgNPs-S-rGO2%@g-C3N4 under the optimised pH(6) and catalyst dosage(25 mg/L) irradiating beneath visible-light (450 nm, 150 watts) for 70 min. The chemical and morphological analysis of AgNPs-S-rGO2%@g-C3N4 surface also supported the possible role of thiolation for this enhancement, assisted by surface plasmon resonance of AgNPs having size < 10 nm. Therefore, AgNPs-S-rGO2%@g-C3N4 has 3772.5 µmolg−1 h−1 H2 production, which is 6.43-fold higher than g-C3N4 having cyclic stability of 96% even after four consecutive cycles. The proposed mechanism for AgNPs-S-rGO2%@g-C3N4 revealed that the photo-excited electrons in the conduction-band of g-C3N4 react with the adhered water moieties to generate H2.

Challenges, Opportunities and Future Directions of Membrane Technology for Natural Gas Purification: A Critical Review.

Natural gas is an important and fast-growing energy resource in the world and its purification is important in order to reduce environmental hazards and to meet the required quality standards set down by notable pipeline transmission, as well as distribution companies. Therefore, membrane technology has received great attention as it is considered an attractive option for the purification of natural gas in order to remove impurities such as carbon dioxide (CO2) and hydrogen sulphide (H2S) to meet the usage and transportation requirements. It is also recognized as an appealing alternative to other natural gas purification technologies such as adsorption and cryogenic processes due to its low cost, low energy requirement, easy membrane fabrication process and less requirement for supervision. During the past few decades, membrane-based gas separation technology employing hollow fibers (HF) has emerged as a leading technology and underwent rapid growth. Moreover, hollow fiber (HF) membranes have many advantages including high specific surface area, fewer requirements for maintenance and pre-treatment. However, applications of hollow fiber membranes are sometimes restricted by problems related to their low tensile strength as they are likely to get damaged in high-pressure applications. In this context, braid reinforced hollow fiber membranes offer a solution to this problem and can enhance the mechanical strength and lifespan of hollow fiber membranes. The present review includes a discussion about different materials used to fabricate gas separation membranes such as inorganic, organic and mixed matrix membranes (MMM). This review also includes a discussion about braid reinforced hollow fiber (BRHF) membranes and their ability to be used in natural gas purification as they can tackle high feed pressure and aggressive feeds without getting damaged or broken. A BRHF membrane possesses high tensile strength as compared to a self-supported membrane and if there is good interfacial bonding between the braid and the separation layer, high tensile strength, i.e., upto 170Mpa can be achieved, and due to these factors, it is expected that BRHF membranes could give promising results when used for the purification of natural gas.

Prewetting Induced Hydrophilicity to Augment Photocatalytic Activity of Nanocalcite @ Polyester Fabric.

To eliminate imidacloprid insecticide from wastewater, nanocalcite was grafted onto the surface of pretreated polyester fabric. The process of seeding was followed by the low temperature hydrothermal method for the growth of nanocalcite for the functionalization of fabric. The goal of this study was to improve the hydrophilicity of the nanocalcite photocatalyst that had been grafted onto the surface of polyester fabric (PF) using acidic and basic prewetting techniques. The morphological characteristics, crystalline nature, surface charge density, functional groups of surface-modified nanocalcite @ PF were determined via SEM, XRD, FTIR, and Zeta potential (ZP), respectively. Characterization results critically disclosed surface roughness due to excessive induction of hydroxyl groups, rhombohedral crystal structure, and high charge density (0.721 mS/cm). Moreover, contact angle of nanocalcite @ PF was calculated to be 137.54° while after acidic and basic prewetting, it was reduced to 87.17° and 48.19°. Similarly, bandgap of the as fabricated nanocalcite was found to be 3.5 eV, while basic prewetted PF showed a reduction in band gap (2.9 eV). The solar photocatalytic mineralization of imidacloprid as a probe pollutant was used to assess the improvement in photocatalytic activity of nanocalcite @ PF after prewetting. Response surface methodology was used to statistically optimize the solar exposure time, concentration of the oxidant, and initial pH of the reaction mixture. Maximum solar photocatalytic degradation of the imidacloprid was achieved by basic prewetted nanocalcite @ PF (up to 91.49%), which was superior to acidic prewetted fabric and as-fabricated nanocalcite @ PF. Furthermore, HPLC and FTIR findings further indicated that imidacloprid was decomposed vastly to harmless species by basic prewetted nanocalcite @ PF.

Immobilization techniques of a photocatalyst into and onto a polymer membrane for photocatalytic activity.

This article reviews the various techniques of immobilizing a photocatalyst into and onto the polymer membrane for pollutant removal and as a problem solver in handling suspended photocatalyst issues from the previous literature. A particular focus is given to the preparation of mixed matrix membranes and deposition techniques for photocatalytic degradation in applications for wastewater treatment. Advantages and disadvantages in this application are evaluated. Various operating conditions during the process are presented. About 90 recently published studies (2008-2020) are reviewed. From the literature, it was found that TiO2 is the most favoured photocatalyst that is frequently used in photocatalytic water treatment. Dry-wet co-spinning and sputtering techniques emerged as the promising technique for immobilizing a uniformly distributed photocatalyst within the polymeric membrane, and exhibited excellence pollutant removal. In general, the technical applicability is the key factor in selecting the best photocatalyst immobilizing technique for water treatment. Finally, the scope of various techniques that have been reviewed may provide potential for future photocatalytic study.

Enhanced Solar Photocatalytic Reduction of Cr(VI) Using a (ZnO/CuO) Nanocomposite Grafted onto a Polyester Membrane for Wastewater Treatment.

Among chemical water pollutants, Cr(VI) is a highly toxic heavy metal; solar photocatalysis is a cost-effective method to reduce Cr(VI) to innocuous Cr(III). In this research work, an efficient and economically feasible ZnO/CuO nanocomposite was grafted onto the polyester fabric ZnO/CuO/PF through the SILAR method. Characterization by SEM, EDX, XRD, and DRS confirmed the successful grafting of highly crystalline, solar active nanoflakes of ZnO/CuO nanocomposite onto the polyester fabric. The grafting of the ZnO/CuO nanocomposite was confirmed by FTIR analysis of the ZnO/CuO/PF membrane. A solar photocatalytic reduction reaction of Cr(VI) was carried out by ZnO/CuO/PF under natural sunlight (solar flux 5-6 kW h/m2). The response surface methodology was employed to determine the interactive effect of three reaction variables: initial concentration of Cr(VI), pH, and solar irradiation time. According to UV/Vis spectrophotometry, 97% of chromium was removed from wastewater in acidic conditions after four hours of sunlight irradiation. ZnO/CuO/PF demonstrated reusability for 11 batches of wastewater under natural sunlight. Evaluation of Cr(VI) reduction was also executed by complexation of Cr(VI) and Cr(III) with 1, 5-diphenylcarbazide. The total percentage removal of Cr after solar photocatalysis was carried out by AAS of the wastewater sample. The ZnO/CuO/PF enhanced the reduction of Cr(VI) metal from wastewater remarkably.

Effective Removal of Cr(VI) from Wastewater Using Biochar Derived from Walnut Shell.

Heavy metals are the major concern of the modern age. Among the heavy metals, chromium (Cr(VI)) is regarded as a highly toxic heavy metal released largely from leather tanning operations. To remove such high concentrations of Cr(VI), an advanced method is required urgently. Thus, biosorption using biochar, which is an organic material produced from various sources such as walnut shell, can be applied successfully for Cr(VI) abatement. The major objectives of this experiment were the remediation of the Cr(VI) heavy metal using walnut shell biochar and checking of the effect of pH, biochar dosage, Cr level, and shaking time. Remediation of Cr(VI) using walnut shell biochar was proved to be effective and removed the maximum concentration of Cr(VI) up to 93% at pH 5.5, 2 h agitation time, and the biochar amount of 1.1 g L-1 from an aqueous solution. Equilibrium modeling demonstrated that the chemisorption process was involved in adsorption of Cr(VI). The surface of the biochar was porous and provided numerous sites for Cr(VI) attachment, which was also confirmed by the presence of Cr(VI) onto the biochar after adsorption. Hence, the use of walnut shell biochar was highly effective as a sorbent, which could conveniently be applied to small-scale as well as large-scale levels.

Fabrication of High Performance PVDF Hollow Fiber Membrane Using Less Toxic Solvent at Different Additive Loading and Air Gap.

Existing toxic solvents in the manufacturing of polymeric membranes have been raising concerns due to the risks of exposure to health and the environment. Furthermore, the lower tensile strength of the membrane renders these membranes unable to endure greater pressure during water treatment. To sustain a healthier ecosystem, fabrication of polyvinylidene fluoride (PVDF) hollow fiber membrane using a less toxic solvent, triethyl phosphate (TEP), with a lower molecular weight polyethylene glycol (PEG 400) (0-3 wt.%) additive were experimentally demonstrated via a phase inversion-based spinning technique at various air gap (10, 20 and 30 cm). Membrane with 2 wt.% of PEG 400 exhibited the desired ultrafiltration asymmetric morphology, while 3 wt.% PEG 400 resulting microfiltration. The surface roughness, porosity, and water flux performance increased as the loading of PEG 400 increased. The mechanical properties and contact angle of the fabricated membrane were influenced by the air gap where 20 cm indicate 2.91 MPa and 84.72°, respectively, leading to a stronger tensile and hydrophilicity surface. Lower toxicity TEP as a solvent helped in increasing the tensile properties of the membrane as well as producing an eco-friendly membrane towards creating a sustainable environment. The comprehensive investigation in this study may present a novel composition for the robust structure of polymeric hollow fiber membrane that is suitable in membrane technology.

High sorption efficiency for As(III) and As(V) from aqueous solutions using novel almond shell biochar.

Arsenic (As) presence in surface reservoirs and groundwater is considered as an extremely alarming issue around the globe. The objectives of the present study were to evaluate the sorption potential of almond shell (ALS) and almond shell biochar (ASB) based sorbents for the removal of As(III)/As(V) from As-contaminated aqueous solutions. The maximum As(III) sorption capacity of ALS and ASB were 4.6 and 4.86 mg g-1, respectively at an initial As concentration of 5 mg L-1, pH ∼ 7.2 and sorbent dose of 0.6 g L-1. Similarly, in case of As(V) the maximum sorption capacities were reported as 3.45 and 3.6 mg g-1 by ALS and ASB respectively. Almond shell biochar removed 10-25% higher As(III)/As(V) compared to the ALS. The isotherm modeling results revealed that both for As(III) and As(V), Langmuir model presented the suitable fit to the equilibrium data compared to other model showing the monolayer sorption to be a dominant sorption mechanism. The FTIR and XPS spectroscopy revealed that mostly -OH functional groups along with some other aromatic and/or aliphatic carbon- and oxygen-rich groups (CC-C, -C-H, CO) were responsible for As sorption by both sorbents. It is concluded that ASB can remove As, notably As(III) from water more efficiently compared to natural ALS. Overall, the results of this research reveal that biochar conversion of ALS can enhance the sorption capacity for As in contaminated waters such as drinking water and wastewater.

Comparative efficiency of peanut shell and peanut shell biochar for removal of arsenic from water.

Contamination of surface water and groundwater streams with carcinogenic chemicals such as arsenic (As) has been a major environmental issue worldwide, and requires significant attention to develop new and low-cost sorbents to treat As-polluted water. In the current study, arsenite (As(III)) and arsenate (As(V)) removal efficiency of peanut shell biochar (PSB) was compared with peanut shell (PS) in aqueous solutions. Sorption experiments showed that PSB possessed relatively higher As removal efficiency than PS, with 95% As(III) (at pH 7.2) and 99% As(V) (at pH 6.2) with 0.6 g L-1 sorbent dose, 5 mg L-1 initial As concentration, and 2 h equilibrium time. Experimental data followed a pseudo-second-order model for sorption kinetics showing the dominance of chemical interactions (surface complexation) between As and surface functional groups. The Langmuir model for sorption isotherm indicated that As was sorbed via a monolayer sorption process. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy analyses revealed that the hydroxyl (-OH) and aromatic surface functional (C=O, C=C-C, and -C-H) groups contributed significantly in the sorption of both As species from aqueous solutions through surface complexation and/or electrostatic reactions. We demonstrate that the pyrolysis of abandoned PS yields a novel, low-cost, and efficient biochar which provides dual benefits of As-rich water treatment and a value-added sustainable strategy for solid waste disposal.