Search

Biodegradation ability of a native bacterial species Pelomonas aquatica strain WS2-R2A-65, isolated from nitramine explosive-contaminated effluent, for octogen (HMX) and hexogen (RDX) under aerobic...

In this manuscript, RDX (Royal Demolition eXplosive) and HMX (High Melting eXplosive) were removed from water that is mainly polluted by military activities. Two different forms of magnetic graphen...

2,4,6-Trinitrophenol (TNP), an explosive utilized for artillery munitions, ends up polluting water and soil. This study targets the treatment of TNP contaminated water via adsorption technique. A comparative adsorption study using pristine rGO (reduced graphene oxide), α-Fe2O3/rGO, bare α-Fe2O3 and physical mixture of α-Fe2O3 & rGO has been carried to select the most suitable adsorbent. To understand the mechanism of adsorption of TNP on α-Fe2O3/rGO adsorption isotherms were applied on adsorption data. The adsorption kinetics followed pseudo second order kinetic model. The mechanism of adsorption changed significantly with change in pH. The maximum adsorption capacity was found to be 769.23 mg · g−1. Regeneration studies indicated that the adsorbent can be used up to 3 times without significant decrease in adsorption efficiency. Magnetic nature of adsorbent allowed its easy segregation from the contaminant solution upon application of external magnetic field. To assess the adsorption efficacy of α-Fe2O3/rGO in real water under ambient condition, TNP was spiked in ground water samples collected from adjoining district that had high TDS (Total dissolved solids). The Langmuir adsorption capacity of 164.24 mg · g−1 was attained with substantial decrease in TDS. Thus α-Fe2O3/rGO proves to be an efficient adsorbent for nitrophenols and can be used commercially for waste water treatment.

An aero-gel based solid solution of titanium and cerium oxide nanoparticles have been used for the first time for ultra fast and trace level removal of arsenic from water. The interconnected long range ordered mesoporous structure was observed from TEM analysis which has been verified as an essential facet for the fast removal of arsenic in this study. The HR-XRD spectra indicated the face centred cubic structure with Fm 3 ¯ m space group. Le-Bail refinement and Raman spectroscopy confirmed the formation of single phase solid solution of Ce1-XTixO2-Y oxide nanoparticles. The HR-XPS and FT-IR study indicated the surface complexation and partial oxidation of As(III) to As(V) via electron transfer mechanism by reduction of Ce(IV) to Ce(III) and Ti(IV) to Ti(III) simultaneously during adsorption process. The kinetics study demonstrated 99% removal of As(III) within 10 min of initiating the adsorption process. The effect of pH and interfering ions confirmed the wide range of applicability for solid solution of titania and cerium oxide nanoparticles over the different environmental conditions for the removal of arsenic. The adsorption capacity for our best adsorbent (Ce0.8Ti0.2O2-y) was found to be 2 × 105 mg kg−1 while the lowest concentration of water body system was 7 μg L−1 which is the minimum concentration of arsenic achieved by any metal oxide based adsorbent.

Magnetic zero valent iron – silica nanocomposite (Fe/SiO2) was synthesized using sol – gel technique followed by in-situ hydrogen reduction. The prepared nanocomposite was characterized by Nitrogen-Brunner–Emmett–Teller (N2-BET) isotherm studies, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) techniques. The Fe/SiO2 nanocomposite demonstrated great adsorption potential against different explosives viz. 2,4-Dinitrotoluene (DNT) and 2,4,6-Trinitrotoluene (TNT) with maximum adsorption capacity of 12.32 and 13.56 mg/g, respectively. Both Langmuir and Freundlich isotherm model fitted well with the experimental data indicating a heterogenous adsorption of these explosives by the nanocomposite. The magnetic Fe/SiO2 nanocomposite could be easily separated after adsorption process with the help of a magnet. A plausible reduction pathway of both the explosives using nanocomposite has also been discussed.

A solid solution of aero-gel based cerium doped iron oxide nanoparticles has been utilized for the first time for ultrasonic wave assisted adsorptive removal of arsenic from aqueous medium. The FE-SEM and HR-TEM images revealed a novel morphology of hollow architectures with irregular distribution in sizes in which the particles are interconnected with each other in a long-range network. The HR-XRD analysis indicated the cubic fluorite type structure with Fm3m space group which is retained even after adsorption of As(III). The Raman study and Lebail refinement confirmed the formation of solid solution of Fe and Ce oxide nanoparticles. The room temperature ferromagnetism was observed for CeO2 NPs (Ms 0.0209 emu g–1) which is attributed to higher concentration of oxygen vacancies and increased (Ms 0.0287 emu g–1) after doping of iron. The adsorption pattern of As(III) is well-defined by Redlich–Peterson isotherm while the adsorption is governed by pseudo-second-order kinetics. The HR-XPS and diffuse reflec...

In this study we have synthesized a high surface area magnetic graphene oxide (MGO) impregnated with α-Fe 2 O 3 for the removal of a toxic textile azodye Eriochrome Black T (EBT). MGO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), fourier transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman, Superconducting quantum interference device (SQUID) and Brunauer-Emmet-Teller (BET) surface area analyzer. Batch adsorption of EBT with MGO was studied using various isotherms and it was found to follow Langmuir monolayer adsorption with 210.53 mg g −1 maximum adsorption capacity. Thermodynamic study indicates the adsorption to be spontaneous and exothermic in nature. The time-dependent adsorption followed pseudosecond order kinetics and intraparticle diffusion model indicates strong initial adsorption and the diffusion is controlled by both boundary layer and intraparticle diffusion. Attempt was made to study the dynamic EBT adsorption, for which a customized filter was prepared. It was observed that MGO has high adsorption capacity in this case as well which led to the conclusion that MGO filters have a great potential to be used commercially, becoming a futuristic adsorbent.

Cerium oxide (CeO2), titanium oxide (TiO2) and titanium oxide impregnated with cerium oxide (Ti@Ce oxide) nanoparticles were synthesized using a simple one-pot surfactant-free method. The synthesized adsorbents were tested against the removal of Cr(VI) from aqueous medium. Comprehensive characterization methods like BET, XRD, SEM, EDAX, HR-TEM, SAED, HR-XPS and FT-IR were performed at different stages of the adsorption process and synthesis. A N2-BET study revealed the large surface area (268 m2 g−1) and pore size (6.8 nm) of CeO2 nanoparticles, which decreased after impregnation of titania. An XRD study demonstrated the phase transformation of TiO2 from the anatase phase to the rutile phase after the impregnation with CeO2 by lowering the phase transformation temperature from >550 °C to 400 °C. Ti0.3@Ce0.7 oxide nanoparticles showed 81% removal of Cr(VI) within 2.5 min of initiating the adsorption process while more than 92% removal of Cr(VI) was achieved within 10 min of adsorption. A HR-XPS study indicated the dual oxidation states of ceria and titania metals, which helped to convert the more toxic Cr(VI) ions to less toxic Cr(III) ions during the adsorption process. The adsorption pattern depicted the monolayer behavior of Cr(VI) obeying the Redlich–Peterson isotherm and followed pseudo second-order kinetics. An intraparticle diffusion model disclosed the surface and pore resistance diffusion of Cr(VI) on the surface of adsorbents.

Aero-gel based one-pot synthesis of anatase phase TiO2 nanoparticles having a high surface area of 125 m2 g−1 has been reported in this work. The humidity sensing perfomance of the obtained porous TiO2 nanoparticles exhibits a quick response (2 s) and fast recovery (1.5 s), negligible hysteresis (

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), a high energy explosive, is used in various military and other applications like nuclear devices, rocket propellants, plastic explosives, rocket fuels, burster chargers construction, quarrying and mining. Generation and unselective disposal of HMX wastes from production sites, detonation fields and unexploded ordinance has resulted in significant environmental contamination of soil and water bodies. Due to its toxicity and persistence in the environment, the study of its biodegradation is highly desirable. Conventional HMX related waste management practices are neither environment friendly, nor cost effective. This work represents a consolidated up-to-date review on HMX, incorporating its production, environmental fate, conventional waste management techniques, and its toxicity and natural remediation (phytoremediation and bioremediation) potential, which may help researchers and implementers as a ready refrence to work with the high energy explosive.

Cerium oxide (CeO2) nanoparticles of size 3–5 nm and surface area 257 m2 g−1 were synthesized using simple, single-pot, and surfactant-free aerogel process. Efforts were made to tune the surface area and porosity of CeO2 nanoparticles by changing the concentration of precursors. CeO2 nanoparticles were characterized by TEM, SEM, XRD, N2-BET, and FTIR. Prepared CeO2 was used to remove As(III) and As(V) from water at variable contaminant concentrations (25–100 ppm) and pH (3–10). The adsorption process found extremely fast for the first few minutes of exposure. CeO2 nanoparticles indicated adsorption capacities of 71.9 and 36.8 mg g−1 against As(III) and As(V), respectively. The adsorption data best fitted with Redlich–Peterson model, depicting monolayer adsorption. The adsorption followed pseudo-second-order kinetics and intraparticle diffusion with three-step diffusion process. The effect of co-existing anions (H2 PO4−, SO42−, and HCO3−) indicated 80–96% reduction in adsorption capacity. © 2017 American Institute of Chemical Engineers Environ Prog, 00: 000–000, 2017

Water contamination has reached an alarming state due to industrialization and urbanization and has become a worldwide issue. Dyes contaminate water and are addressed extensively by researchers. Various technologies and materials have been developed for the treatment of contaminated water. Among them, adsorption has attracted great attention due to its ease and cost-effective nature. In recent years, graphene-based composites have shown great potential for the removal of contaminants from water. The literature reveals the usefulness of composites of graphene with metal oxides, carbon derivatives, metal hybrids and polymers for the removal of organic dyes from contaminated water. In this review, efforts have been made to compile the studies on the removal of cationic and anionic dyes from water using graphene-based composites.

Silica nanoparticles with a surface area of 673.60 m2/g and particle size of 8–12 nm were prepared using aerogel process (AP) followed by super critical drying. Zero valent Fe, Co, Pt, and bimetallic Fe/Pt and Fe/Co were loaded using an incipient wetness impregnation technique and subsequent reduction. Scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy-energy dispersive X-ray (TEM-EDX) characterizations indicated fine dispersion of iron on AP-SiO2 +Fe system. Prepared nanoparticles were evaluated for the adsorptive removal of 2,4,6-trinitrotoluene (TNT) from water. Surface area normalized rate constant values indicated the adsorptive removal potential of prepared nanoparticles to be: AP-SiO2 + Fe/Co > AP-SiO2 + Fe > CM (commercial) SiO2 + Fe > AP-SiO2 + Co > AP-SiO2 + Fe/Pt > AP-SiO2 + Pt. Lower pH helped in accelerating the reactive removal of TNT on zero valent iron loaded silica. AP-SiO2 + Fe/Co system showed the maximum adsorption potential (74 mg/g) after five cycles.