Fernando Martínez

Heterogeneous catalytic wet peroxide oxidation systems for the treatment of an industrial pharmaceutical wastewater.

The aim of this work was to assess the treatment of wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using an Fe(2)O(3)/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80 degrees C using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for complete carbon depletion and initial pH of ca. 3 allow TOC degradation of around 50% after 200 min of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55h of reaction. Furthermore, the BOD(5)/COD ratio is increased from 0.20 to 0.30, whereas the average oxidation stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.

Heterogeneous photo-Fenton treatment for the reduction of pharmaceutical contamination in Madrid rivers and ecotoxicological evaluation by a miniaturized fern spores bioassay.

Fifty-six pharmaceuticals of various chemical groups, such as anti-inflammatory, antibacterial and cardiovascular drugs, were detected in four selected river waters receiving sewage effluents in the Community of Madrid (Spain). A promising approach for the degradation of those residues is the application of a photo-Fenton treatment. Several new bioassays using fern spores were employed for the evaluation of acute and chronic toxicity based on mitochondrial activity, DNA and chlorophyll quantifications of as-received river water and photo-Fenton-treated samples. photo-Fenton treatment provided a high degree of total organic carbon mineralization with up to 70% reduction for river water samples. In addition, the elimination of most of the studied pharmaceutical compounds was confirmed. A few compounds, however (salicylic acid, ofloxacin, caffeine, cotinine and nicotine), seemed more resistant, with after-treatment concentrations between 4 and 44ngL(-1). Nicotine showed the most refractory behaviour with concentrations ranging from 29 to 224ngL(-1) for treated samples. Photo-Fenton treatment yielded a significant decrease in acute and chronic toxicity, even though some residual toxicity remained after treatment. This fact seemed to be related to the presence of toxicants in the water matrix, probably of inorganic nature, rather than the toxic effect of the studied pharmaceutical compounds, as revealed by the effective removal of these compounds and high TOC mineralization of photo-Fenton treatments.

Acid hybrid catalysts from poly(styrenesulfonic acid) grafted onto ultra-large-pore SBA-15 silica using atom transfer radical polymerization

Poly(styrenesulfonic acid)-functionalized materials based on poly(styrenesulfonic acid sodium salt) incorporated via aqueous atom transfer radical polymerization (ATRP) initiated from the surface of large-pore mesoporous SBA-15 silica support have been synthesized. The inorganic–organic nature of these hybrid materials makes them particularly desirable for acid-catalyzed reactions that require extended and hydrophobic surface areas with a narrow pore diameter distribution in the mesoporous range. Acidic hybrid materials were prepared by grafting the ATRP-initiator (3-(chlorodimethylsilyl)propyl bromoisobutyrate) on the silica surface, subsequent polymerization of the styrenesulfonic acid sodium salt monomer, and final sodium ion exchange by acid activation. Conventional and ultra-large-pore SBA-15 silica supports with nominal (BJH) pore diameter ranging from 8 to 32 nm were used for the incorporation of different polymer loadings at different polymerization times. The silylation of ATRP-initiator-functionalized SBA-15 supports has allowed a better control of the ATRP within the mesoporous structure. The use of ultra-large-pore SBA-15 supports provides a remarkable increase of the porosity which allowed us to properly allocate the polymer. The hybrid poly(styrenesulfonic acid)-modified materials showed good catalytic activities in the esterification of oleic acid with n-butanol, particularly in terms of intrinsic activity per acid site.

Influence of synthesis routes on the state of Fe-species in SBA-15 mesoporous materials

Four different iron-containing SBA-15 based mesoporous materials have been prepared. The first three (DS-1, DS-2 and DS-3) are synthesised directly from the same synthesis gel containing iron—just modifying the second ageing step at different pH values (<1, 3.5, and 7 respectively). The fourth substance (PS sample) is a grafted material, with iron impregnated after the synthesis. The materials contain iron in different extents and states: with ionic dispersion in DS-1, whereas large hematite crystals are embedded into DS-2 and DS-3 samples. The post-synthesis modification of PS results in deposition of iron oxide particles of 3–6 nm most probably within the pore channels. Samples have been characterized among other methods by XRD, TEM and Mossbauer spectroscopy. Although the materials have profoundly different structures, all of them exhibit good activity in the catalytic oxidation of phenol with hydrogen peroxide in aqueous media. In particular, those samples which have embedded hematite particles display even remarkable hydrothermal stability in this process.

Effect of Ultrasound on the Properties of Heterogeneous Catalysts for Sono-Fenton Oxidation Processes

Abstract The objective of this research is to assess the effect of ultrasonic irradiation (20 KHz) on the catalytic activity and catalyst particle size of different iron-containing solids (hematite/SBA-15 nanocomposite; hematite; goethite). The catalytic activities of the different catalysts were investigated in the sono-Fenton degradation of a phenolic aqueous solution in the presence of hydrogen peroxide at pH 3. The catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions. The concentration changes of different by-products coming from incomplete mineralization of phenol were also monitored. The stability was examined by measuring iron dissolved in the reaction medium after reaction. The degradation rate in the presence of the nanocomposite material was higher than that when SBA-15 and hematite were separately suspended and also higher than that found for the bulk and unsupported iron oxides (hematite and goethite). The particle size of the catalysts suffers serious changes during the sonication which strongly depend on their nature. Unlike nanocomposite material which presents a deep catalyst particle reduction, unsupported bulk iron oxides yield an agglomeration of the particles. The considerable enhancement of the activity achieved with the nanocomposite material is due to the catalyst particles size reduction during ultrasound irradiation as well as the high dispersion of the metallic species over the mesostructured support.

Intensified-Fenton process for the treatment of phenol aqueous solutions

An intensified-Fenton process for the treatment of phenol aqueous solutions has been studied as a continuous catalytic wet hydrogen peroxide oxidation system. This process consists of coupling the catalytic activity of a heterogeneous Fenton-like catalyst with the homogeneous contribution of its dissolved iron species. Agglomerated mesoporous SBA-15 silica-supported iron oxide (Fe₂O₃/SBA-15) material was used as heterogeneous catalyst. The influence of the reaction temperature and the initial hydrogen peroxide dosages was studied in order to minimize the operation cost of the process. The catalytic performance of the process was assessed in terms of total organic carbon (TOC) and hydrogen peroxide conversions. Likewise, the stability of the solid Fenton-like catalyst was also evaluated in terms of the dissolved iron species. The increase of the reaction temperature enhanced the TOC conversion and reduced the iron leaching from the heterogeneous catalyst. These results were related to the degradation of oxalic acid as responsible for iron extraction by formation of soluble stable iron complexes into the aqueous medium. Finally, the use of a moderate hydrogen peroxide concentration (2.6 g/L) and milder temperatures (80-120 °C) has led to remarkable results of TOC and phenol reductions as well as oxidant efficiency through the intensified-Fenton process.

Catalytic wet hydrogen peroxide oxidation of a petrochemical wastewater

Continuous Catalytic Wet Hydrogen Peroxide Oxidation (CWHPO) for the treatment of a petrochemical industry wastewater has been studied on a pilot plant scale process. The installation, based on a catalytic fixed bed reactor (FBR) coupled with a stirred tank reactor (STR), shows an interesting alternative for the intensification of a continuous CWHPO treatment. Agglomerated SBA-15 silica-supported iron oxide (Fe(2)O(3)/SBA-15) was used as Fenton-like catalyst. Several variables such as the temperature and hydrogen peroxide concentration, as well as the capacity of the pilot plant for the treatment of inlet polluted streams with different dilution degrees were studied. Remarkable results in terms of TOC reduction and increased biodegradability were achieved using 160 degrees C and moderate hydrogen peroxide initial concentration. Additionally, a good stability of the catalyst was evidenced for 8 hours of treatment with low iron leaching (less than 1 mg/L) under the best operating conditions.

Catalytic Wet Peroxide Oxidation Process for the Continuous Treatment of Polluted Effluents on a Pilot Plant Scale

Abstract Catalytic Wet Peroxide Oxidation (CWPO) for the continuous treatment of a phenolic aqueous solution has been studied on a pilot scale process. The pilot plant has been designed by integration of a catalytic fixed bed reactor (FBR) with a continuous stirred tank reactor (CSTR). The CSTR is used as reservoir for the continuous delivering of a recirculation stream through the catalytic bed. The main part of phenol mineralization takes place by catalytic oxidation in the FBR. The mesoporous SBA-15 silica-supported iron oxide (Fe2O3/SBA- 15) agglomerated with bentonite has been selected as catalyst, according to preliminary studies for the continuous treatment of phenolic aqueous solutions in a catalytic packed-bed reactor operating in upflow (1). The efficiency of the wet peroxide oxidation treatment under different operation conditions has been evaluated in terms of phenol degradation, total organic carbon (TOC) reduction and hydrogen peroxide conversion. Among the main operation conditions, the feed and recirculation liquid flow rates, the catalyst loading and the temperature in the CSTR were studied. The increase of the residence time as the feed flow rate is reduced has shown a remarkable improvement of the process efficiency, whereas the variation of the recirculation flow through the FBR has slightly affected the overall catalytic performance. A significant enhancement of the process efficiency has been also found as the temperature of the CSTR was increased up to 80 °C. Under the most favourable operating conditions, phenol was almost totally degraded (99%) and TOC was reduced up to ca. 63% at steady-state conditions. In concern to the catalyst stability, a low dissolution of iron within the aqueous solution during the process has been proven.

ZVI Addition in Continuous Anaerobic Digestion Systems Dramatically Decreases P Recovery Potential: Dynamic Modelling

The objective of this study is to show the preliminary results of a (dynamic) mathematical model describing the effects of zero valent iron (ZVI) addition during the anaerobic digestion of waste activated sludge from wastewater treatment systems. A modified version of the Anaerobic Digestion Model No. 1 (ADM1) upgraded with an improved physico-chemical description, ZVI corrosion, propionate uptake enhancement and multiple mineral precipitation is used as a modelling platform. The proposed approach is tested against two case studies which correspond to two lab scale anaerobic digesters (AD2, AD1), with and without adding ZVI, respectively, and running in parallel for a period of 87 days. Experimental results show that ZVI enhances methane production. However, the P recovery potential is dramatically reduced as soluble P decreased by one order of magnitude in AD2 with respect to AD1. Simulations demonstrate that the model is capable to satisfactorily reproduce the dynamics of hydrolysis, acetogenesis, acidogenesis, nutrient release, pH and methanogenesis in the control anaerobic digester (AD1). This study also evidences the enhancement of methane production by the influence of ZVI on the acidogenesis and methanogenesis processes in AD2. In addition, it also identifies saturation conditions for siderite (FeCO3) and vivianite (Fe3(PO4)2), which causes changes in the biogas composition (% CH4 versus % CO2) and P release (lower values). This is the first study analysing the decrease of P recovery potential due to the addition of ZVI into AD systems.

New URJC-1 Material with Remarkable Stability and Acid-Base Catalytic Properties

Emerging new metal-organic structures with tunable physicochemical properties is an exciting research field for diverse applications. In this work, a novel metal-organic framework Cu(HIT)(DMF)0.5, named URJC-1, with a three-dimensional non-interpenetrated utp topological network, has been synthesized. This material exhibits a microporous structure with unsaturated copper centers and imidazole–tetrazole linkages that provide accessible Lewis acid/base sites. These features make URJC-1 an exceptional candidate for catalytic application in acid and base reactions of interest in fine chemistry. The URJC-1 material also displays a noteworthy thermal and chemical stability in different organic solvents of different polarity and boiling water. Its catalytic activity was evaluated in acid-catalyzed Friedel–Crafts acylation of anisole with acetyl chloride and base-catalyzed Knoevenagel condensation of benzaldehyde with malononitrile. In both cases, URJC-1 material showed very good performance, better than other metal organic frameworks and conventional catalysts. In addition, a remarkable structural stability was proven after several consecutive reaction cycles.