Javier Araña

• PhD
• University of Las Palmas de Gran Canaria

Two series of new photocatalysts were synthesized based on modification with Pd of the commercial P25 photocatalyst (EVONIK®). Two techniques were employed to incorporate Pd nanoparticles on the P25 surface: photodeposition (series Pd-P) and impregnation (series Pd-I). Both series were characterized in depth using a variety of instrumental techniqu...

In this study, the photocatalytic activity in hydrogen production of a TiO2 catalyst with hierarchical structure and microsphere morphology was tested. This catalyst was synthesised by hydrolysis and condensation processes from a Ti(OBut)4 precursor and calcined at 150 °C, 400 °C and 630 °C. Hydrogen production of the subsequent photocatalysts rose...

A study was undertaken of the adsorption and photocatalytic conversion of NO, NO2 and NO3⁻/HNO3 using two photocatalysts (P25 and HT-ET). The HT-ET is a catalyst synthesized in our laboratory comprised only of anatase phase and with a surface area three times larger than that of the P25. In powder form, the catalyst was introduced into and extended...

In this work, novel TiO2-based nanobelts with various phases were synthesized: biphasic TiO2(B)/anatase, pure TiO2(B) and pure anatase. These catalysts were obtained via hydrothermal reaction using two nanoparticulated TiO2 photocatalysts as precursors: Aeroxide TiO2 P25 (P25) and TiO2 synthesized via a sol-gel process (SG). In addition, the surfac...

A hybrid constructed wetland mesocosm has been used for the treatment of raw urban wastewater. The first stage was a mulch-based, subsurface, horizontal flow constructed wetland (HF). The HF achieved good removals of COD (61%; 54 g/m²·day) and Total Suspended Solids (84%; 29 g/m²·day). The second stage was composed of vertical flow constructed wetl...

Fenton-based processes have been studied for the mineralization and detoxification of wastewaters from the postharvest of fruit, which were contaminated with the fungicide imazalil (IMZ). For this purpose, studies were carried out in a simulated agro-industrial wastewater. Statistical design of experiments was used to assess the influence of IMZ, F...

A study is undertaken of the effect of fluorinating two TiO2 catalysts, both with the same surface area but one composed only of pure anatase phase (SA) and the other of mixed anatase and rutile phases (P25), on the degradation of phenol, formic acid and aniline. The catalysts were characterised by FTIR, BET, EDAXs, SEM, XRD and DRS-UV–vis studies....

TiO2 deactivation processes during gas-phase degradation of ethanol were studied. To force the deactivation processes, various cycles were performed, avoiding the degradation of acetates. It was observed that acetates adsorbed on the anatase phase of catalysts provoke the transference of electrons to surface traps which modify the electron states o...

The effects of silver and palladium metals on the photocatalytic degradation of diclofenac sodium salt (DCF), isoproturon (IP) and phenol (PHL) in water over lab-made TiO2 synthesized following a sol–gel method were investigated. Silver and palladium catalysts were prepared by photodeposition at 1 wt.% of loading metal. The resulting materials were...

Fenton and photo-Fenton processes were tested for the treatment of wastewater from a local textile industry in Ecuador. The goal of this research was to obtain an efficient, easy-to-apply method for the removal of colour, organic compounds, biodegradability, resistant pollutants, and toxicity according to the Vibrio fischeri bioluminescence test. T...

In this work, titanium dioxide has been modified by sulfation, fluorination and simultaneous Pt nanoparticles deposition; the influence of these treatments on the photocatalytic activity of this oxide has been studied. A complete characterization study was carried out and it was observed that sulfation, fluorination and metallization were important...

In this work we present the results of the application of photocatalytic techniques to organic pollutants in water. Such aqueous wastes are produced during the UV–Vis spectrophotometric determination of the NH 4 + ion in water. Processes taking place during the photocatalytic degradation of such organics have been studied by using FTIR, HLPC and TO...

A comparison is made in this study of the effectiveness of various commercial catalysts in the oxidation of NOx by heterogeneous photocatalysis. The following catalysts were considered: Aeroxide TiO2 P25, Aeroxide TiO2 P90, Hombikat UV-100, Kronos vlp7000, CristalACTIV PC105, CristalACTIV PC500, Kemira 650 and Anatasa Aldrich. All catalysts were de...

Differences in the gas-phase photocatalytic degradation of NH3 and ethanol in the presence of water over two commercial TiO2 materials with different structural characteristics (Evonik's P25 (P25) and Sigma Aldrich's anatase (SA)) were established here using FTIR. The materials were characterized using different techniques including BET, XRD, UV-vi...

This work studies the elimination, mineralization and detoxification through Fenton-based processes of wastewaters contaminated with the fungicide imazalil as a result of the postharvest treatment of bananas. Fe(II) and H2O2 concentrations were optimized for degradation of the corresponding imazalil concentrations. The activity of the imazalil degr...

Abstract In this study, the photoactivity of commercial and lab-made TiO2 when immobilized on different supports, namely borosilicate glass, alumina foam and refractory brick, was examined for the removal of the fungicide imazalil from different water matrices. Alumina foam provided the largest exposed photocatalyst surface but degradation kinetics...

In this work we studied the elimination, mineralization and detoxification of wastewaters from banana postharvest industries, contaminated with the fungicide imazalil, by means of heterogeneous advanced oxidation processes. We compared the activity of the commercial photocatalyst Evonik P25 and the lab-made EST-1023t in the degradation of imazalil...

Sol–gel synthesised TiO2 developed by our group was modified through the addition of nickel nitrate and ammonium carbonate in the synthesis process. Photocatalysts were synthesised with different Ni/Ti molar ratios (0.015, 0.030, 0.045) and constant Ni/N ratio equal to 1.5 and subjected to post-calcination at temperatures of between 400 °C and 700...

A laboratory-scale, intermittently fed, organic-based vertical flow filter was tested as a pre-treatment of high-strength urban wastewater to reduce the risk of clogging in treatment wetlands. At an average hydraulic loading rate of 815 L/m2 day and average surface loading rates of biological oxygen demand of 458 g/m2 day, chemical oxygen demand of...

TiO2 Degussa P25, TiO2 prepared by sol–gel submitted to sulfation pre-treatment and some metallized catalysts obtained by photodeposition of Au or Pt over the sulfated TiO2, were evaluated in the reaction of ethanol photo-oxidation. FT-IR spectroscopy was used to investigate the surface features of the photocatalysts, identifying adsorbed species a...

The elimination and mineralization of the fungicide imazalil and its by-products has been studied by means of heterogeneous photocatalysis. The activity of different photocatalysts, including the commercial TiO2 benchmark photocatalyst (Evonik P25) and several TiO2-based lab-made catalysts, is compared. The best results were achieved with the new l...

2,4-dichlorophenol (DCP) was decomposed in the presence of TiO2 suspensions by illumination. The operating variables that were studied included initial DCP concentration, photocatalyst doses and initial pH. Mineralisation was slow at the optimum pH (12) for DCP degradation, with the optimum pH for both degradation and mineralisation being pHo 5. Th...

A Ti–H2O2–phenol complex, not described until now, has been identified on the surface of Degussa P-25 and the new catalyst ECT-1023. This complex is considered to be responsible for the higher hydroquinone to catechol concentration ratio. It has been also shown that phenolates identified on the surface modify electrodonation that controls the gener...

The photocatalytic degradation of the commercial dye Lanaset Sun Yellow 180 was studied in the presence and absence of the different additives used in the dye's formulation. The experiments were performed with Degussa P25 as received and doped with Fe (Fe-TiO(2)) and a new catalyst synthesized by our research group (ECT-1023). The best efficiency w...

In this work we compared the photocatalytic activity of sol–gel synthesized nanocrystalline TiO2 material (ECT-1023t) and a commercial TiO2 (Degussa P25) in the elimination, mineralization and detoxification of waters contaminated by the herbicide bentazon and its toxic intermediates under UV light. Adsorption and kinetics studies were undertaken a...

A comparative study of the photoefficiency of two different TiO2 catalysts in the elimination, mineralization and detoxification of waters containing herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and toxic intermediates was performed at laboratory scale. Commercial TiO2 (Degussa (Evonik) P25) and TiO2 synthesized by citrate sol–gel method (ECT-1...

The degradation and detoxification towards the duckweed Lemna minor of 4-nitrophenol (4NP) was studied by means of bench-scale constructed wetlands (CWs), TiO(2)-photocatalysis and Fenton + photoFenton reactions. The main goal of this work was to compare the three treatment techniques to evaluate their possible combination for the efficient, low co...

The degradation by Fenton and photo-Fenton of high concentrations of ethylene glycol (1000–25,000 mg/L), similar to those found in wastewater has been studied. Strongly exothermic reactions led to temperature increments up to 70–94 °C. In most experiments, temperature increments favored radical formation that provided almost complete mineralization...

The performance of a demonstration natural wastewater treatment system composed of a facultative pond and a horizontal flow constructed wetland (CW) treating raw wastewater from a University Campus has been studied for 5 years. The system achieved high removals for BOD (94 %), COD (78 %), TOC (72 %), suspended solids (96 %) and turbidity (85 %). El...

New TiO2 catalysts have been synthesised by means of a sol–gel method in which aggregates have been selected before thermal treatment. Sieving and calcination temperature have been proved to be key factors in obtaining catalysts with greater photoactivity than that of Degussa P-25. These new catalysts have been characterized by means of transmissio...

The performance of two substrates commonly available in the zone, gravel and lapilli, was tested for their use in hybrid constructed wetland pilot plants for the treatment and reuse of urban wastewater in Gran Canaria, Canary Islands, Spain. The first stage of the systems was a vertical subsurface-flow constructed wetland and the second stage was a...

The photocatalytic efficiency of different TiO2 catalysts in the degradation of 2-propanol in gas phase has been studied. The obtained efficiencies have been compared considering the distribution of rutile–anatase phases, surface area, particle size, distribution of surface hydroxyl groups and Brönsted or Lewis acid centres. The catalysts used were...

The effect of the mixing ZnO with different portions of activated carbon (AC) has been studied. The resulting catalysts were characterised and evaluated in the photocatalytic decomposition of aqueous pollutants. Changes in the catalyst colour and in the FTIR vibration bands of the surface hydroxyl groups were recorded. νOH vibrations were shifted t...

Dissolved biochemical demand (BOD), total organic carbon (TOC) and NH(4)-N were analysed in seven sampling points in a pond-wetland system treating raw wastewater from 200 1 to 2005 to determine the efficiency of its constructive elements. The wetland consists of horizontal flow stone filters, free water wetlands and a final subsurface flow wetland...

Formalin wastewater containing high concentrations of formaldehyde and TOC was treated and detoxified with biological aerated filter (BAF) and wetland reactors. At similar formaldehyde loading rates (about 0.01-0.9 kg/m3 d) both reactors provided high efficiencies but the BAF was more efficient at treating formaldehyde and TOC with average eliminat...

The photocatalytic degradation of an endocrine disruptor (resorcinol) and of two fungicides (pyrimethanil and triadimenol) has been studied and compared. The effect of pH, oxygen, and H(2)O(2) on the photocatalytic degradation of these compounds has been established. The three organics were analyzed by means of high pressure liquid chromatography (...

Phenol and phenol compounds are toxic organics that can be found in many industrial wastewaters. Biological wastewater treatments are considered to be the most convenient methods owing to their efficiency and low economic cost. Nonetheless, many organic pollutants are refractory to bacterial degradation. Photocatalytic methods can be an interesting...

The photocatalytic degradation of phthalic acid (H2Ph) with TiO2 (Degussa P-25) and Zno (Aldrich) at different pHs and substrate concentrations (10-150 ppm) has been studied. The concentration and mineralization of H2Ph has been monitored. Results in optimal conditions are: ko = 6.63·10−4 s−1, %TOC = 86.02 for TiO2 and ko = 12.7·10−4 s−1, %TOC=81.9...

Phenol and formaldehyde are toxic compounds present in many industrial wastewaters. Particularly, in synthetic resin producing industries the concentrations of one or both of these organics can reach concentrations of grams per litre. In the present work, the degradation of phenol, formaline (formaldehyde: methanol mixture) and their mixtures with...

In the present work the photocatalytic and biological degradation of two commercial mixtures of pesticides (Folimat and Ronstar) and two fungicides (pyrimethanil and triadimenol) has been studied. The evolution of some components of these commercial products (dicofol, tetradifon and oxadiazon) and that of the two fungicides has been monitored by me...

The photocatalytic degradation of phthalic acid (H2Ph) with TiO2 (Degussa P-25) and ZnO (Aldrich) at different pHs and substrate concentrations (10-150 ppm) has been studied. The concentration and mineralization of H2Ph has been monitored. Results in optimal conditions are: ko = 6.63 · 10⁻⁴ s⁻¹, %TOC = 86.02 for TiO2 and ko = 12.7 · 10⁻⁴ s⁻¹, %TOC...

The photocatalytic techniques have been widely applied to the treatment of wastewaters. However, this work introduces an innovative application of photocatalysis to the treatment in continuous of gaseous contaminants. Packed reactors with different lengths and a spiral one have been designed to study the photocatalytic degradation of methyl tert-bu...

The effect of the presence of formic, oxalic and acetic acids on photocatalytic degradation of p-nitrophenol has been studied. Adsorption and FTIR studies indicated that the presence of such acids modifies p-nitrophenol interaction with TiO2 surface, which is more rapidly degraded. The higher degradation rate constants have been correlated with int...

The kinetics and adsorption aspects of the photocatalytic degradation of three cresolic isomers were studied in aqueous suspension containing TiO2 (Degussa P-25). The Langmuir–Hinshelwood model (L–H) was applied to the kinetic results. Degradation kinetic constants were similar for the three compounds (o-cresol, 0.0188 ppm/s; m-cresol, 0.0166 ppm/s...

The photocatalytic degradation of catechol, resorcinol, m-cresol, o-cresol and phenol has been studied individually, in dual mixtures and in the presence of hydrogen peroxide to determine possible competition for adsorption and photoactive centres and for the radicals photogenerated.The obtained results have shown that in the presence of hydrogen p...

With the goal of predicting the photocatalytic behaviour of different phenolic compounds (catechol, resorcinol, phenol, m-cresol and o-cresol), their adsorption and interaction types with the TiO(2) Degussa P-25 surface were studied. Langmuir and Freundlich isotherms were applied in the adsorption studies. The obtained results indicated that catech...

Heterogeneous photocatalytic degradation of many organic pollutants, such as phenol and phenol derivatives, may be optimised if the catalyst surface saturation and the appearance and accumulation of non-photocatalytically degradable intermediates is avoided. It has been shown that under certain concentration threshold the highest degradation effici...

The photocatalytic features of TiO2 doped with ferric oxides or mixed with activated carbon (AC-TiO2) are compared with those of the unmodified Degussa P-25 TiO2. These new catalysts show specific structural features that alter catechol and resorcinol photodegradabilities, according to their chemical structures. For instance, we have observed that...

The photocatalytic mineralization of methanol, ethanol and 1-propanol is compared with those of their homologous carboxylic acids (formic, acetic and propanoic). The presence of S2O82− ions almost does not affect the alcohols mineralization. But, those of the acids are slowed down. In addition to this, adding H2O2 inhibits the alcohols mineralizati...

The photocatalytic degradation of catechol and resorcinol with TiO2 in presence of acetic acid has been studied. Low concentrations of the acid (30-50 ppm) can modify the adsorption and degradation of the dihydroxybenzenes. However, the acetic acid concentration threshold at which effects are observed depends on the compound. FTIR analyses have sho...

Propan-1-ol and butan-1-ol photo-degradation with TiO2 (bare-TiO2) and TiO2 doped with Pd or Cu has been studied in a gaseous continuous flow system. Exhaust gases have been analysed by means of GC and FTIR. During propan-1-ol and butan-1-ol degradations, catalysts were not deactivated. Nevertheless, important differences in concentrations and dist...

The photocatalytic degradation of three dihydroxybenzenes (hydroquinone, catechol and resorcinol) by TiO2 and Cu-TiO2 has been studied. Degradation rates depend on the molecule catalyst surface interaction type. FTIR studies have shown that Cu presence modifies the organics interactions with the catalysts surface. Therefore, catalysts have shown di...

Aqueous p-nitrophenol solutions are not as hazardous as the solid compound.

In this study the different processes occurring on the TiO2 and Pd and Cu doped TiO2 surfaces during the photocatalytic formic acid degradation in the presence or absence of S2O82− or H2O2 have been investigated. FTIR studies have shown the relevance of the H-bounded hydroxyl groups. It has been observed that formate molecules interact simultaneous...

In this study the different processes occurring on the TiO2 and Pd and Cu doped TiO2 surfaces during the photocatalytic formic acid degradation in the presence or absence of S2O82− or H2O2 have been investigated. FTIR studies have shown the relevance of the H-bounded hydroxyl groups. It has been observed that formate molecules interact simultaneous...

In this paper the degradation of gaseous alcohols (methanol, ethanol, 1-propanol and 1-butanol) has been studied in a continuous reaction system. Methanol and ethanol, but not 1-propanol and 1-butanol, have caused the catalyst bare-TiO2 to become deactivated. The catalyst containing activated carbon, AC-TiO2, has not shown almost deactivation in an...

Ethanol degradation by TiO2 and TiO2 doped with Fe, Pd and Cu has undergone FTIR spectroscopic study. Ethanol interaction with bare-TiO2 and Fe-TiO2 yields the formation of ethoxides on the catalyst surface that can readily be oxidised to acetates by radicals O2− and OH. Conversely, ethanol interaction with Pd-TiO2 and Cu-TiO2 generates an intermed...

The photocatalytic destruction of methanol, formaline (mixture of formaldehyde, methanol and water) and formaline wastes from the preservation of vertinarian physiologic samples has been attempted by two different processes, at high concentrations of reagents and by dossification of reagents, varying pH in both. Experiment evolution has been monito...

In the present work, the effect of mixing TiO2 with different portions of activated carbon (AC) has been studied. Transmission electron microscopy (TEM), scanning electron micrograph (SEM), laser scattering, FTIR and UV spectrophotometric analysis have shown changes of some of the TiO2 physico-chemical characteristics in catalysts containing an AC...

It has been demonstrated that the modification of the TiO2 acid–base properties by the presence of activated carbon (AC) considerably modify the interaction of some molecules with the catalyst surface and hence its photocatalytic characteristics.FTIR studies have shown that while phenol interacts with TiO2 yielding a phenoxide, in the catalyst low...

Different methods such as KMnO4 oxidation, TiO2-photocatalysis and photo-Fenton reaction have been employed for the degradation of wastes from the spectrophotometric determination of in seawater. The optimisation of the degradation process was determined by total organic carbon (TOC) measurements. Experimental parameters such as pH, TiO2, H2O2, Fe3...

The photocatalytic degradation of organic carboxylic acids by Fe-doped TiO2 has been studied. Results indicate that Fe is extracted by means of the formation of a [Fe-carboxylic acid]n+ complex by which the organic molecule is degraded. Fe2+ ions that remain in solution after the degradation go back to the catalyst surface due to their reaction wit...

In the present work, the effect of mixing TiO2 with different portions of activated carbon (AC) has been studied. Transmission electron microscopy (TEM), scanning electron micrograph (SEM), laser scattering, FTIR and UV spectrophotometric analysis have shown changes of some of the TiO2 physico-chemical characteristics in catalysts containing an AC...

Solar TiO2-photocatalysis was applied to waters from a natural wastewater treatment plant located in the Universidad de Las Palmas de Gran Canaria. Degussa P-25 TiO2 and its mixture with activated carbon (AC–TiO2) were used as catalysts. The presence of ozone and certain ions such as phosphates on the photocatalytic degradation of organic matter wa...

In this work we present the results of the application of photocatalytic techniques to organic pollutants in water. Such aqueous wastes are produced during the UV–Vis spectrophotometric determination of the NH4+ ion in water. Processes taking place during the photocatalytic degradation of such organics have been studied by using FTIR, HLPC and TOC...

The photocatalytic degradation of maleic acid by using Fe-doped (0.15, 0.5, 2 and 5% w/w in Fe) TiO2 catalysts has been studied. Catalysts with the lowest Fe content (0.15 and 0.5%) show a considerably better catalytic behavior than non-doped TiO2 and catalysts with higher Fe contents. Maleic acid molecules interact with the surface of the lowest F...

The photocatalytic degradation of maleic acid by using Fe-doped (0.15, 0.5, 2 and 5% w/w in Fe) TiO2 catalysts has been studied. Catalysts with the lowest Fe content (0.15 and 0.5%) show a considerably better catalytic behavior than non-doped TiO2 and catalysts with higher Fe contents. Maleic acid molecules interact with the surface of the lowest F...

Phenol degradation by Photo-Fenton reaction has been studied in highly concentrated wastewaters and most intermediate species have been identified by Fourier Transform IR-Spectroscopy with ATR device. During the photodegradation of highly concentrated phenol solutions, the formation of dissolved and precipitate tannin has been observed. The possibi...

The photocatalytic degradation of formic acid by Fe-doped (0.5, 2 and 5% w/w in Fe) and calcined (773 and 1073 K) TiO2 has been studied. For 773 K calcined catalyst, results suggest that Fe is extracted through the formation of a [FeOOCH]2+ complex by which formic acid degrades. Fe2+ ions that remain in solution after formic acid degradation go ba...

Silica-supported PdZn catalysts have been studied in CO and CO2 hydrogenation and in ethylene hydroformylation. The dilution of surface Pd by Zn lowers the hydrogenating capability of the catalysts and favours the production of higher hydrocarbons in CO hydrogenation. The catalyst with a molar ratio Pd?:?Zn = 3 showed an enhanced ability to insert...

The degradation of high phenol and 1,2-propylene glycol concentrations (1 g/l) in water solutions by TiO2-photocatalysis has been studied. Important differences between the degradation mechanism of both molecules have been observed. From the obtained data it may be suggested that degradation of phenol takes place onto the catalyst surface by means...

The degradation of high phenol concentrations (1 g/L) in water solutions by TiO2 photocatalysis and the photo-Fenton reaction has been studied. From the obtained data it may be suggested that degradation of phenol by TiO2-UV takes place onto the catalyst surface by means of peroxo-compounds formation. At low phenol concentrations other mechanism, t...

The degradation of high phenol concentrations (I g/L) in water solutions by TiO2 photocatalysis and the photo-Fenton reaction has been studied. From the obtained data it may be suggested that degradation of phenol by TiO2-UV takes place onto the catalyst surface by means of peroxo-compounds formation. At low phenol concentrations other mechanism, t...

We report the behaviour of a silica-supported Pd–Zn catalyst in the hydrogenation of CO (total pressure=20 bar, T=548–598 K). Unusual high selectivity to higher hydrocarbons and higher oxygenated products (ethanol and acetaldehyde) was observed. An in-situ DRIFT study under reaction conditions, with analysis by mass spectrometry of products evolved...

In this paper we present the results of the application of conventional and photocatalytic methods for the treatment of hazardous laboratory wastes. Liquid wastes from the spectrophotometric determination of NH+4 as indophenol have been chosen as model samples. The waste composition is rather heterogeneous, as phenol, ethanol, nitroprusside and cit...

In this paper we present the results of the photocatalytic disinfection of urban waste water. Two microbial groups, total coliforms and Streptococcus faecalis, have been used as indexes to test disinfection efficiencies. Different experimental parameters have been checked, such as the effect of TiO2, solar or UV-lamp light and pH. Disinfection of w...

The interaction between CO2 and the silica-supported PtSn alloy gave rise to an infrared band at 2339 cm−1 which was assigned to the coordination of this molecule to the bimetallic phase. The coadsorption of CO and CO2 indicates that both compete for similar coordination sites on the supported PtSn alloy. A CO singleton vibration frequency at ca. 2...

Silica-supported bimetallic MSn (M = Ni, Pd, Pt) samples have been prepared by two consecutive impregnation steps with solutions of [MCl2(PPh3)2] complexes and SnCl2, respectively. After treatment in H2 at 673 K, these materials were characterized in detail by X-ray diffraction (XRD), conventional transmission electron microscopy, combined with ene...

The degradation of the real formaldehyde wastewater by several techniques has been studied. The wastewater was produced in the Veterinary Faculty (ULPGC). Monitoring the degradation kinetics, their efficiencies have been compared. The techniques are classified in two: Homogeneous photocatalytics and chemical processes. Photo-Fenton was the photocat...