Extent Of Mineralization Research Articles

Photocatalytic Degradation of Organic Reactive Dyes over MnTiO3/TiO2 Heterojunction Composites Under UV‐Visible Irradiation

In this study, the photocatalytic degradation of organic reactive dyes have been investigated using MnTiO3/TiO2 heterojunction composites in the presence of electron acceptors under UV-Visible light irradiation. This MnTiO3/TiO2 heterojunction composites were prepared by annealing different mass ratios of pyrophanite MnTiO3 (3-11 wt%) and TiO2 at 300°C. All the MnTiO3/TiO2 heterojunction composites were characterized by spectral techniques like X-ray diffraction (XRD), scanning electron microscope (SEM) and diffused reflectance UV-visible spectroscopic analysis (DRS). Among them, 9 wt% MnTiO3/TiO2 heterojunction composites exhibited higher photocatalytic activity for the degradation of Reactive Blue 4 (RB 4). The photocatalytic efficiency of 9 wt% MnTiO3/TiO2 heterojunction composites was further enhanced by the addition of substantial amount of electron acceptors like hydrogen peroxide (H2O2) and ammonium peroxydisulfate ([NH4]2S2O8). The presence of oxidants (electron acceptors) facilitates the fast degradation of dye solution even in higher concentration upto 200 mg/L. The photocatalytic activity of MnTiO3/TiO2 heterojunction composites was also studied for the degradation of other four different structured reactive dyes. The extent of mineralization of these organic reactive dyes during photocatalytic degradation was estimated from COD analysis. MnTiO3/TiO2 heterojunction composites was also found to have good photostability in the presence of oxidants.

Intensification of degradation of imidacloprid in aqueous solutions by combination of hydrodynamic cavitation with various advanced oxidation processes (AOPs)

The degradation of imidacloprid (a systemic chloronicotinoid insecticide) has been carried out in the aqueous solutions using the combination of hydrodynamic cavitation (HC) with various other advanced oxidation processes such as fenton, photo-fenton, photolytic and photocatalytic processes. HC+fenton process significantly enhanced the rate of degradation of imidacloprid, which lead to a complete degradation of imidacloprid within 15min of operation using the molar ratio of imidacloprid:H2O2 as 1:40 and the molar ratio of FeSO4·7H2O:H2O2 as 1:40. Similar results of an increase in the rate of degradation of imidacloprid have also been obtained in case of HC+photo-fenton process. Synergetic index of 3.636 and 2.912 have been obtained using HC+fenton and HC+photo-fenton processes respectively. The combination of hydrodynamic cavitation with photolytic and photocatalytic processes have also resulted in the enhancement in the rate of degradation of imidacloprid, however synergetic effect has not been observed. Comparison of efficiency of all the processes applied has also been done by computing extent of mineralization achieved and energy requirement of the process.

Effect of surface modification of nanofibres with glutamic acid peptide on calcium phosphate nucleation and osteogenic differentiation of marrow stromal cells

Biomineralization is mediated by extracellular matrix (ECM) proteins with amino acid sequences rich in glutamic acid. The objective of this study was to investigate the effect of calcium phosphate deposition on aligned nanofibres surface-modified with a glutamic acid peptide on osteogenic differentiation of rat marrow stromal cells. Blend of EEGGC peptide (GLU) conjugated low molecular weight polylactide (PLA) and high molecular weight poly(lactide-co-glycolide) (PLGA) was electrospun to form aligned nanofibres (GLU-NF). The GLU-NF microsheets were incubated in a modified simulated body fluid for nucleation of calcium phosphate crystals on the fibre surface. To achieve a high calcium phosphate to fibre ratio, a layer-by-layer approach was used to improve diffusion of calcium and phosphate ions inside the microsheets. Based on dissipative particle dynamics simulation of PLGA/PLA-GLU fibres, > 80% of GLU peptide was localized to the fibre surface. Calcium phosphate to fibre ratios as high as 200%, between those of cancellous (160%) and cortical (310%) bone, was obtained with the layer-by-layer approach. The extent of osteogenic differentiation and mineralization of marrow stromal cells seeded on GLU-NF microsheets was directly related to the amount of calcium phosphate deposition on the fibres prior to cell seeding. Expression of osteogenic markers osteopontin, alkaline phosphatase (ALP), osteocalcin and type 1 collagen increased gradually with calcium phosphate deposition on GLU-NF microsheets. Results demonstrate that surface modification of aligned synthetic nanofibres with EEGGC peptide dramatically affects nucleation and growth of calcium phosphate crystals on the fibres leading to increased osteogenic differentiation of marrow stromal cells and mineralization.

Solar photo-Fenton oxidation against the bioresistant fractions of winery wastewater

This work examined the solar-photo Fenton oxidation against the bioresistant fractions of winery wastewater. Winery effluents already treated by a membrane bioreactor (MBR) were subjected to further purification by solar photo-Fenton oxidation process (hv/Fe2+/H2O2). The effect of various operating variables, such as the catalyst and oxidant concentration, as well as temperature and solar irradiation on the abatement of chemical oxygen demand (COD), dissolved organic carbon (DOC), color, toxicity and phytotoxicity has been assessed. Optimum Fe2+ and H2O2 concentrations were found to be 3mgL−1 and 250mgL−1, respectively. Solar photo-Fenton has been demonstrated to be an effective process for the purification of winery effluents, yielding after 120min of treatment, COD, DOC and color removal of 70±3.3%, 53±3.7% and 75±2.2%, respectively. The residual COD and DOC values after the end of the solar treatment were 33mgL−1 and 14.1mgL−1, respectively. In the various operating conditions studied, the extent of mineralization (assessed by DOC) was lower than the COD decrease, implying that partial oxidation reactions of the organic content prevailed over total oxidation to CO2 and water. Moreover, the process efficiency was found to increase with temperature up to a point (∼70% at 25°C), and then reach a plateau with a small increase by further increasing the temperature to 45°C. Finally, the toxic and the phytotoxic compounds still present in the effluent after the biological treatment were reduced or even eliminated through solar photo-Fenton oxidation.

Synergetic effect of combination of AOP's (hydrodynamic cavitation and H2O2) on the degradation of neonicotinoid class of insecticide

In the present work, degradation of imidacloprid (neonicotinoid class of insecticide) in aqueous solution has been systematically investigated using hydrodynamic cavitation and combination of hydrodynamic cavitation (HC) and H2O2. Initially, effect of different operating parameters such as inlet pressure to the cavitating device (5–20bar) and operating pH (2–7.5) has been investigated. Optimization of process parameters was followed by the study of effect of combination of HC and H2O2 process on the rate of degradation of imidacloprid. Significant enhancement in the rate of degradation of imidacloprid has been observed using HC+H2O2 process which lead to a complete degradation of imidacloprid in 45min of operation using optimal molar ratio of imidacloprid:H2O2 as 1:40. Substantial synergetic effect has been observed using HC+H2O2 process which confer the synergetic coefficient of 22.79. An attempt has been made to investigate and compare the energy efficiency and extent of mineralization of individual and combined processes applied in the present work. Identification of the byproducts formed during degradation of imidacloprid has also been done using LC–MS analysis. The present work has established a fact that hydrodynamic cavitation in combination with H2O2 can be effectively used for degradation of imidacloprid.

Preliminary radiogenic isotope study on the origin of the Khanneshin carbonatite complex, Helmand Province, Afghanistan

The REE-mineralized Khanneshin carbonatite complex in southern Afghanistan is an economically light rare earth element (LREE)-enriched carbonatite complex of Quaternary age. Geological studies have suggested that the LREE-enriched rocks at Khanneshin are comparable in grade to many economic REE deposits, including parts of the world-class Bayan Obo (China), and Mountain Pass, California (United States) deposits. The extent of mineralization at Khanneshin is unknown; however, mineralized areas delineated as part of a reconnaissance study are estimated to contain ~1.29Mt REE ore. We have determined for the first time the radiogenic isotope compositions (Pb–Sr–Nd) of bulk rocks and mineral separates (barite, strontianite, carbonate, etc.) of this carbonatite complex and propose the likely source of radiogenic isotope reservoirs associated with the REE mineralization. This study provides an opportunity to establish fundamental isotopic features of this highly mineralized system to aid in regional exploration efforts and to identify other comparable mineralized systems that shared similar source reservoirs, origins, and evolution in southern Afghanistan.The carbonatite complex consists of coarse-grained sövite and brecciated and agglomeratic barite–ankerite alvikite. Small satellitic intrusions of biotite–calcite carbonatite and rare leucite phonolite also crop out. The massif is encircled by alkali metasomatized Neogene sedimentary strata. A peripheral apron of volcanic and volcaniclastic strata extends farther away from the complex. Present-day Pb isotopic compositions of bulk rocks (dikes, welded tuffs, sövite, and mineralized rocks) and mineral separates exhibit a narrow range in 206Pb/204Pb (18.814–18.877), 207Pb/204Pb (15.616–15.674), and 208Pb/204Pb (38.892–39.094). The results show that the source region of the carbonatite had a moderate compositional variation (most samples overlapping within the level of analytical precision). Present-day neodymium isotopic compositions from the Khanneshin carbonatite show a range in 143Nd/144Nd (0.512374–0.512462). Present-day strontium isotopic compositions also have a moderate range in 87Sr/86Sr (0.708034–0.709577); the mineral separates and ore are somewhat less radiogenic in 87Sr/86Sr (0.707954–0.708686) than the whole rocks.A fundamental feature of the Khanneshin carbonatite is the overall high degree of isotopic homogeneity evident for the Nd–Sr–Pb isotopic systems and we regard this consistency as a diagnostic feature related to its evolution. The carbonatite constitutes a unique isotopic target for identification of other mineralized systems that might have shared the same source. The bulk rocks and minerals in the deposit are generally analytically isotopically indistinguishable, regardless of the mineralogical complexities. All rocks and minerals shared radiogenic isotopic reservoirs, a common evolution, and have remained in isotopic equilibrium. Isotope variations eliminate the source of MORB rocks, or depleted mantle (DMM), as a significant reservoir to the Khanneshin carbonatite. Compared to model mantle reservoirs, the Pb and Nd isotopes of the Khanneshin carbonatite roughly suggest source combinations of enriched mantle, type EMI and HIMU. Sr isotopic data highlight the contribution of another source (EMII?) to account for the relatively high values of 87Sr/86Sr. The radiogenic isotope compositions of the Khanneshin carbonatite differ from world-class REE-mineralized systems such as Bayan Obo (China) and Mountain Pass (California).

Insights into solar TiO2-assisted photocatalytic oxidation of two antibiotics employed in aquatic animal production, oxolinic acid and oxytetracycline

In this study, solar driven TiO2-assisted heterogeneous photocatalytic experiments in a pilot-plant with compound parabolic collectors (CPCs) were carried out to study the degradation of two authorized veterinary antibiotics with particular relevance in finfish aquaculture, oxolinic acid (OXA) and oxytetracycline (OTC), using pure solutions of individual or mixed antibiotics. Firstly, the influence of natural solar photolysis was assessed for each antibiotic. Secondly, photocatalytic degradation kinetic rate constants for individual and mixed antibiotics were compared, using a catalyst load of 0.5gL−1 and an initial pH around 7.5. Thirdly, for individually photocatalytic-treated OXA and OTC in the same conditions, the growth inhibition of Escherichia coli DSM 1103 was followed, and the mineralization extent was assessed by the residual dissolved organic carbon (DOC), low-molecular-weight carboxylate anions and inorganic ions concentration. Finally, the effect of inorganic ions, such as chlorides, sulfates, nitrates, phosphates, ammonium and bicarbonates, on the photocatalytic degradation of individual solutions of OXA and OTC was also evaluated and the formation of different reactive oxygen species were probed using selective scavengers. The removal profiles of each antibiotic, both as single component or in mixture were similar, being necessary 2.5kJL−1 of solar UV energy to fully remove them, and 18kJUVL−1 to achieve 73% and 81% mineralization, for OXA and OTC, respectively. The remaining organic carbon content was mainly due to low-molecular-weight carboxylate anions. After complete removal of the antibiotics, the remaining degradation by-products no longer showed antibacterial activity. Also, 10% and 55% of the nitrogen content of each antibiotic was converted to ammonium, while no conversion to nitrite or nitrate was detected. The presence of phosphates hindered considerably the removal of both antibiotics, whereas the presence of other inorganic ions did not substantially altered the antibiotics photocatalytic degradation kinetics.

Photocatalytic oxidation of Rhodamine B with ferric oxide thin films under solar illumination

Thin films of iron oxide are synthesized by spray pyrolysis technique using ferric chloride as precursor in non-aqueous medium. The effect of solution concentration onto photochemical, structural, morphological, optical, luminescence and thermal properties has been investigated. Structural analysis confirms the rhombohedral crystal structure with strong (110) orientation. Raman spectrum reveals that the deposited films contain α-phase of Fe2O3 (hematite). The SEM images of optimized Fe2O3 thin films show microneedle like structure with varying grain size from 75 to 120nm. The observed direct band gap is about 2.0eV for Fe2O3 thin film. Room temperature photoluminescencespectra showed three pronounced emission peaks for all concentrations. The photocatalytic oxidation of Rhodamine B with hematite Fe2O3 thin films under solar illumination is investigated. The first order rate constants for this heterogeneousphotocatalysis are evaluated as a function of the initial concentration of Rhodamine B (RhB). The extent of mineralization of degraded sample is confirmed by total organic carbon (TOC) andchemical oxygen demand (COD)analysis. This work suggests that prepared iron oxide photoelectrodes demonstrate an excellent ability to remove toxic dyes from industrial wastewater.

Complete mineralization of surfactant from aqueous solution by a novel sono-synthesized nanocomposite (TiO2–Cu2O) under sunlight irradiation

In this study, a new method has developed for the synthesis of TiO2–Cu2O nano-composite with high optical absorption in the visible range and high photocatalytic activity in mineralization of sodium dodecyl-benzenesulfonate (SDBS) in an ultrasonic bath with low intensity at 40kHz. The results of EDAX, TEM and XRD confirmed the purity, crystallinity and the structure of the nanocomposite particles with the size less than 10nm. Ultrasound played a key role in the formation of nanocomposite with highest photocatalytic activity in mineralization of SDBS under sunlight. The degradation of SDBS by sunlight irradiation showed that the extent of mineralization depends on the operating conditions. In addition, the TiO2–Cu2O that contained 5% (mole ratio) TiO2 exhibited better photocatalytic activity than either Cu2O or TiO2 alone or other composites with different mole ratios. So that, the mineralization percentage of SDBS in the solution reached to 100% after 90min and the mineralization on the surface of the catalyst was completed after 240min. The data obtained from the degradation experiments fit the first-order kinetics and the adsorption obeyed the Langmuir model.

Photodegradation of dimethyldisulfide by heterogeneous catalysis using nanoCdS and nanoCdO embedded on the zeolite A synthesized from waste porcelain

Photodegradation of dimethyldisulfide (DMDS) was examined using nanoCdS and nanoCdO loaded on zeolite A as a heterogeneous catalyst under UV irradiation. Zeolite A was prepared from waste porcelain. Cadmium sulfide nanoparticles were prepared by a precipitation method using zeolite A as a template. Finally, CdO/A was prepared by wet impregnation of parent zeolite NaA with Cd(NO3)2 solution. Fourier transformation infrared, X-ray diffraction, and scanning electron microscopy methods were applied for the characterization of samples. UV–Vis spectrophotometric measurements were performed to determine the extent of decolorization and mineralization. Considering the influence of experimental parameters such as catalyst concentration, DMDS concentration, and pH of the test solutions, the contaminant photoelimination process was studied. The optimal operation parameters were found as follows: pH 1, 0.3g L−1 of catalyst loading, and 8 ppm of DMDS concentration. Based on the obtained results in the photodegradation process of DMDS, the most efficiency was detected in the presence of nanoCdS/A, while no remarkable activity was perceived when bulkCdS was used as the photocatalyst. CdO/A and nanoCdS particles also showed relatively good activities in the photodegradation extent of the contaminate. The degradation process obeyed first-order kinetics.

Degradation of sulfamethoxazole by persulfate assisted micrometric Fe0 in aqueous solution

Persulfate (PS) chemical activation using micrometric Fe0 particles (MIPs) was tested on sulfamethoxazole (SMX) solution (39.5μM). MIPs load (0.89–17.85mM), PS content (0.4–1.0mM), pH (5.50–8.30) and alkalinity (bicarbonate) were investigated for the improvement of SMX degradation. Optimum conditions for the enhancement of the reaction stoichiometric efficiency (RSE=5.2%) were developed. HPLC–MS results confirmed that SMX was converted into its reduced form through cleavage of the isoxazole N–O bond by two routes: (i) electron abstraction upon sulfate radicals (SRs) attack yielding non stable radical cation SMX+ or (ii) electron addition through Fe0 oxidation yielding unstable radical anion SMX−. In both cases, the final transformation product was identified as b-aminoenone after acceptance of electrons originated from the MIPs surface and protons present in the acidic medium. This suggested that PS activated into SRs was responsible of the rapid degradation of SMX and its transformation product as well in contrast to Fe0 alone. Different water matrices were evaluated in order to understand the role that dissolved ions play on the reaction degradation rate. Successive experiments (n=3) of 1h each conducted on remaining Fe0 showed complete SMX degradation. The extent of SMX mineralization under the experimental conditions reached 37% making from Fe0/PS system an excellent source of SRs able to sustain oxidation reactions in aqueous media of slightly acidic pH.

Decolorization of a binary azo dyes mixture using CuO incorporated nanozeolite-X as a heterogeneous catalyst and solar irradiation

The photodecolorization of a mixture of the methylene blue and rhodamine B cationic dyes was studied using CuO/nano-zeolite X catalyst under solar irradiation. Nano-zeolite crystals were synthesized by hydrothermal crystallization. The photocatalyst was prepared by the calcinations process at 450°C for 12h followed by anion exchange process of the parent nano-zeolite NaX in a copper(II) sulfate aqueous solution (0.2M) for 24h. All samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), BET and diffuse reflectance spectroscopy (DRS) methods. The particles sizes of the nano-zeolite NaX crystals were calculated in the ranges of 7–10nm and 75–85nm by XRD and SEM, respectively. The decolorization extent of the dyes in their mixture was measured spectrophotometrically at their respective λmax values. The decolorization kinetics was fitted well to the Langmuire–Hinselwood first order rate law. The effects of various operating parameters including pH, the amount of the catalyst, the amount of loaded CuO, the initial dyes concentrations, H2O2 and KBrO3 doses on the photodecolorization efficiency were studied at atmospheric conditions. The chemical oxygen demand (COD) experiments were performed at regular intervals to confirm the mineralization extent of the dyes.

Aerobic Biodegradation Kinetics and Mineralization of Six Petrodiesel/Soybean-Biodiesel Blends

The aerobic biodegradation kinetics and mineralization of six petrodiesel/soybean-biodiesel blends (B0, B20, B40, B60, B80, and B100), where B100 is 100% biodiesel, were investigated by acclimated cultures. The fatty acid methyl esters (FAMEs) of biodiesel were found to undergo rapid abiotic transformation in all experiments. The C10-C21 n-alkanes of petrodiesel were metabolized at significantly higher microbial utilization rates in the presence of biodiesel. The rates of mineralization of the blends were also enhanced in the presence of biodiesel; yet a similar enhancement in the extent of mineralization was not observed. Abiotic fuel-blends/aqueous-phase equilibration experiments revealed that the FAMEs of biodiesel were capable of cosolubilizing the n-alkanes of petrodiesel, a mechanism that fully explains the faster utilization and mineralization kinetics of petrodiesel in the presence of biodiesel without necessarily enhancing the extent of biomineralization. The biodegradation of six targeted aromatic compounds present in petrodiesel was also influenced by the amount of biodiesel in a blend. While toluene, o-xylene, and tetralin were not degraded in the B0 and B20 treatments, all of the targeted aromatic compounds were degraded to below detection limits in the B40 and B80 treatments. Biomass acclimated to B60, however, was unable to degrade most of the aromatic compounds. These results indicate that the amount of biodiesel in a blend significantly affects the absolute and relative abundance of the dissolved and bioavailable constituents of biodiesel and petrodiesel in a way that can considerably alter the biodegrading capacity of microbial cultures.

Enhanced Photocatalytic Degradation of Reactive Dyes over FeTiO3/TiO2 Heterojunction in the Presence of H2O2

In this work, photocatalytic degradation of two reactive dyes, Reactive Yellow 84 (RY 84) and Reactive Black 5 (RB 5), on FeTiO3/TiO2 heterojunction in the presence of UV–visible radiation and H2O2 has been reported. FeTiO3/TiO2 heterojunction has been prepared from ilmenite FeTiO3 and anatase TiO2 by employing oxalic acid as an organic linker. FeTiO3/TiO2 ratios have been varied from 1 to 5 wt.%, and the materials were characterized by X-ray diffraction, scanning electron microscope and diffused reflectance UV–visible spectroscopic analysis. The photocatalytic activity of FeTiO3/TiO2 heterojunction for the degradation of the organic dyes RY 84 and RB 5 in the presence of UV–visible light was found to be higher than that of pure TiO2. The addition of H2O2 increases the rate of degradation of both dyes on FeTiO3/TiO2 heterojunction. It facilitates the fast degradation of dye solutions even when their concentration was above 100 mg/l, which is otherwise very slow due to the low transmittance of light by the dye solution. The extent of mineralisation of the reactive dye during photocatalytic degradation was estimated from chemical oxygen demand analysis. FeTiO3/TiO2 heterojunction photocatalyst was also found to have good photostability; the material retains almost 97 % of its initial activity even in the fifth cycle.

The nature and formation of cristobalite at the Soufrière Hills volcano, Montserrat: implications for the petrology and stability of silicic lava domes

Cristobalite is commonly found in the dome lava of silicic volcanoes but is not a primary magmatic phase; its presence indicates that the composition and micro-structure of dome lavas evolve during, and after, emplacement. Nine temporally and mineralogically diverse dome samples from the Soufrière Hills volcano (SHV), Montserrat, are analysed to provide the first detailed assessment of the nature and mode of cristobalite formation in a volcanic dome. The dome rocks contain up to 11 wt.% cristobalite, as defined by X-ray diffraction. Prismatic and platy forms of cristobalite, identified by scanning electron microscopy (SEM), are commonly found in pores and fractures, suggesting that they have precipitated from a vapour phase. Feathery crystallites and micro-crystals of cristobalite and quartz associated with volcanic glass, identified using SEM-Raman, are interpreted to have formed by varying amounts of devitrification. We discuss mechanisms of silica transport and cristobalite formation, and their implications for petrological interpretations and dome stability. We conclude: (1) that silica may be transported in the vapour phase locally, or from one part of the magmatic system to another; (2) that the potential for transport of silica into the dome should not be neglected in petrological and geochemical studies because the addition of non-magmatic phases may affect whole rock composition; and (3) that the extent of cristobalite mineralisation in the dome at SHV is sufficient to reduce porosity—hence, permeability—and may impact on the mechanical strength of the dome rock, thereby potentially affecting dome stability.

Riverine Flux of Metals from Historically Mined Orefields in England and Wales

The flux of metals at the tidal limits of major rivers are an important metric of freshwater contaminant transfer to marine habitats, reported in Northeast Atlantic bordering countries under the 1992 Oslo-Paris (OSPAR) Convention. This paper presents an assessment of long-term OSPAR data for four trace metals (Cd, Cu, Pb, and Zn) using a range of spatial datasets to assess the broad distribution of metal flux and yield across England and Wales. Mine site records and geological and land use data are used to classify river basins into six classes. The bulk of metal flux to seas around England and Wales occurs from catchments containing extensive mineralization and a legacy of metal mining (52 % of the total Zn flux, 47 % of Pb, 39 % of Cu, and 48 % of Cd were associated with mined catchments). Catchment area, metal flux from point mine discharges at source, and extent of mineralization typically accounted most for variation in catchment outlet metal flux in stepwise multiple linear regression (SMLR). There are a number of small mining-impacted rural catchments contributing significant fluxes of metals to coastal waters. Of particular prominence are Restronguet Creek (drainage area 87 km2) in southwest England that discharges 176 t Zn/year and 18 t Cu/year and the Afon Goch Dulas (27 km2) in north Wales, which releases 20 t Zn/year and 9 t Cu/year. Although such exercises cannot directly determine the provenance of metals, comparison with metal release data and a review of catchment-scale studies suggest a critical role of mining-related contaminants in contributing to catchment metal export.

Biochar-Mediated [14C]Atrazine Mineralization in Atrazine-Adapted Soils from Belgium and Brazil

Biochar addition to soil has been reported to reduce the microbial degradation of pesticides due to sorption of the active compound. This study investigated whether the addition of hardwood biochar alters the mineralization of (14)C-labeled atrazine in two atrazine-adapted soils from Belgium and Brazil at different moisture regimens. Biochar addition resulted in an equally high or even in a significantly higher atrazine mineralization compared to the soils without biochar. Statistical analysis revealed that the extent of atrazine mineralization was more influenced by the specific soil than by the addition of biochar. It was concluded that biochar amendment up to 5% by weight does not negatively affect the mineralization of atrazine by an atrazine-adapted soil microflora.

Kinetic Analysis of Heterogeneous Photocatalysis: Role of Hydroxyl Radicals

This article provides the current research activities that concentrate on the role of hydroxyl radicals in heterogeneous photocatalysis by transition metal oxides for different nanostructures. We devote most attention to Al-based Fe2O3 nanostructures that have been synthesized using chemical methods. The visible light photocatalytic activity of nanocrystalline pure and Al-based Fe2O3 photocatalysts for degradation of Salicylic acid, 4-Cholorphenol, and Acid orange 7 (Azo dye) is reported. The catalytic activity and selectivity for organic species are remarkably influenced by the size of the different photocatalyst. Utilization of various structures, advanced oxidation processes, heterojunction between Al-based Fe2O3 and TiO2, and application of solar energy for heterogeneous photocatalysis of water impurities were discussed. Extent of complete mineralization of such compounds by measuring COD and TOC was discussed. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials for photocatalysis might be directed.

Ferric iron amendment increases Fe(III)-reducing microbial diversity and carbon oxidation in on-site wastewater systems

Onsite wastewater systems, or septic tanks, serve approximately 25% of the United States population; they are therefore a critical component of the total carbon balance for natural water bodies. Septic tanks operate under strictly anaerobic conditions, and fermentation is the dominant process driving carbon transformation. Nitrate, Fe(III), and sulfate reduction may be operating to a limited extent in any given septic tank. Electron acceptor amendments will increase carbon oxidation, but nitrate is toxic and sulfate generates corrosive sulfides, which may damage septic system infrastructure. Fe(III) reducing microorganisms transform all major classes of organic carbon that are dominant in septic wastewater: low molecular weight organic acids, carbohydrate monomers and polymers, and lipids. Fe(III) is not toxic, and the reduction product Fe(II) is minimally disruptive if the starting Fe(III) is added at 50–150mgL−1. We used 14C radiolabeled acetate, lactate, propionate, butyrate, glucose, starch, and oleic acid to demonstrate that short and long-term carbon oxidation is increased when different forms of Fe(III) are amended to septic wastewater. The rates of carbon mineralization to 14CO2 increased 2–5times (relative to unamended systems) in the presence of Fe(III). The extent of mineralization reached 90% for some carbon compounds when Fe(III) was present, compared to levels of 50–60% in the absence of Fe(III). 14CH4 was not generated when Fe(III) was added, demonstrating that this strategy can limit methane emissions from septic systems. Amplified 16S rDNA restriction analysis indicated that unique Fe(III)-reducing microbial communities increased significantly in Fe(III)-amended incubations, with Fe(III)-reducers becoming the dominant microbial community in several incubations. The form of Fe(III) added had a significant impact on the rate and extent of mineralization; ferrihydrite and lepidocrocite were favored as solid phase Fe(III) and chelated Fe(III) (with nitrilotriacetic acid or EDTA) as soluble Fe(III) forms.

Transformation products and reaction kinetics in simulated solar light photocatalytic degradation of propranolol using Ce-doped TiO2

The visible light photocatalytic degradation of propranolol was studied using cerium doped titanium dioxide, a catalyst that showed an increased light absorption in the visible region. The experiments were carried out in ultrapure water and in a biologically treated wastewater from the secondary effluent of a treatment plant spiked with propranolol. The best results were obtained for a cerium loading of 0.5wt.% and a bulk catalyst concentration of 0.14g/L, with which propranolol became essentially depleted after 1.5h of irradiation. The extent of mineralization reached 17.4% after 6h on stream under the same conditions. Both oxidation on catalyst holes and reaction with hydroxyl radicals contribute to propranolol depletion, but for the reaction conditions tested in this study, the first mechanism predominated and accounted for 60% of the propranolol rate constant. The runs performed in wastewater matrix led to a very low photocatalytic rate compared with pure water, which was attributed to the presence of radical scavengers and competing substances. Over thirty reaction intermediates were detected by means of exact mass measurements performed by liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (LC-ESI-QTOF–MS/MS) based on the characteristic fragmentation of oxidation by-products. Their relative abundance was also assessed in catalytic and non-catalytic runs. The most abundant transformation products could be attributed to the cleavage of the ether bond of propranolol. Other compounds detected derived from the addition of hydroxyl groups to the aromatic nuclei or to the ring-opening attack of hydroxyl radicals on the naphthol moiety. Finally, the toxicity of oxidized mixtures was determined using the green algae Pseudokirchneriella subcapitata and the bioluminescent marine bacterium Vibrio fischeri. Although the toxicity of treated mixtures tended to decrease as propranolol was depleted, mixtures treated in pure water may lead to the accumulation of toxic transformation products.