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A new synthesis method to prepare the heterostructured catalyst MIL-101(Fe) derived Fe2O3 with TiO2 via microwave-assisted sol-gel route followed by pyrolysis was carried out. The mixed oxide catalyst was characterized by high-resolution transmission electron (HRTEM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Vis DRS spectroscopy, N2 physisorption, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), photoluminescence (PL), and zetametry. The photocatalytic activity was evaluated in the degradation of the nonsteroidal anti-inflammatory drugs (NSAIDs), ibuprofen (IBP), and naproxen (NPX) in a mixture (10 mg/L/each one) at pH 3, using 1 g/L of the catalyst under visible light. The synthesized Fe2O3/TiO2 showed higher surface area, smaller average crystallite size, absorption in the visible range, and narrower band gap than TiO2, which enhanced the photocatalytic performance of TiO2 under visible radiation, allowing 91 and 100% degradation of IBP and NPX within 240 and 15 min of reaction, respectively. Moreover, 79.0% of mineralization of the mixture of NSAIDs in 240 min was achieved using the derived Fe2O3/TiO2 showing good reusability and stability even after three cycles of usage. In the photocatalytic process, holes were the dominant species for NSAIDs degradation.

Porous carbon derived from amine-functionalized MIL-125 metal-organic framework (C-MIL-125-NH2) was prepared by carbonization at high temperature under inert atmosphere, and used for adsorption of bisphenol A (BPA) and 4-tert-butylphenol (4-tBP). The obtained carbon showed bimodal porosity and fast extraction of both pollutants in batch conditions following a pseudo-second-order model. The adsorption mechanism was studied by the measurement of zeta potential, and the results suggested that π-π stacking interactions between the carbon material and the phenol molecules probably are the main sorption mechanism. The prepared C-MIL-125-NH2 was incorporated into mechanically stable membranes for flow-through solid-phase extraction of studied phenols prior to HPLC analysis. The hybrid material showed excellent permeance to flow, easy regeneration and good performance for the simultaneous enrichment of mixtures of BPA and 4-tBP, facilitating their determination when present at low concentration levels.

The photocatalytic activity of boron-doped ZnO with varying concentration (1, 1.5 and 2% wt of B) synthesized by sol-gel method was evaluated on cyanide (CN−) degradation in aqueous solution under simulated solar radiation. The obtained catalysts were characterized by XRD, UV–vis/DRS, ICP-OES, FT-IR, and XPS. The photocatalytic experiments were carried out in a quartz batch reactor using 300 mL of cyanide solution adjusted at pH 11, evaluating different parameters such as the amount of B dopant, catalyst loading and initial concentration of cyanide solution. A 23 central composite faced design was used to maximize CN− photocatalytic degradation. The cyanide concentration was measured by ISE potentiometric method and the content of intermediate ions (OCN−, NO3−, and NH4+) was determined by UV–vis spectrophotometry. The boron incorporation into ZnO lattice (ZnO-B) reduced wurtzite crystallite size (25 nm) and narrowed the band gap (3.0 eV) compared to bare ZnO (43 nm and 3.2 eV, respectively). The ZnO-B 1.5 wt% showed better photocatalytic performance by degrading 89% of a 10 mg L-1 CN− solution compared to 75% that was reached by undoped ZnO; using in both cases 1.4 g L-1 of catalyst loading at accumulated energy of 400 kJ m-2.

In this work, a novel P-doped Fe2O3-TiO2 mixed oxide was successfully prepared by a microwave assisted sol-gel method. The synthesized catalyst was characterized by N2 physisorption, SEM, XRD, XPS, and FTIR, UV–vis DRS, and PL spectroscopies. The iron and phosphorus content in the catalyst samples were quantified by AAS and ICP-OES, respectively. The photocatalytic activity of P-doped Fe2O3-TiO2 powders were evaluated in the photocatalytic degradation of sulfamethazine (SMTZ). The Box Behnken design (BBD) and response surface methodology (RSM) were applied for modeling the effect and optimizing of the operational parameters levels on the degradation percentage of SMTZ. The complete degradation and mineralization percentage of 30% of SMTZ solution at pH 9 was achieved within 300 min of reaction, with the optimum P doping amount of 1.2 wt % and 1.25 g/L of catalyst loading. The 1.2 wt % P-doped Fe2O3-TiO2 mixed oxide showed considerably higher photocatalytic activity than Fe2O3-TiO2 or TiO2. This enhanced performance could be attributed to the small crystallite size, narrow band gap, high specific surface area and increased number of surface hydroxyls on TiO2 nanoparticles. Additionally, the stability and reusability of this catalyst was demonstrated during three cycles of SMTZ degradation.

A fully automated on-line system for monitoring the TiO2-based photocatalytic degradation of dimethyl phthalate (DMP) and diethyl phthalate (DEP) using sequential injection analysis (SIA) coupled to liquid chromatography (LC) with UV detection was proposed. The effects of the type of catalyst (sol–gel, Degussa P25 and Hombikat), the amount of catalyst (0.5, 1.0 and 1.5 g L−1), and the solution pH (4, 7 and 10) were evaluated through a three-level fractional factorial design (FFD) to verify the influence of the factors on the response variable (degradation efficiency, %). As a result of FFD evaluation, the main factor that influences the process is the type of catalyst. Degradation percentages close to 100% under UV-vis radiation were reached using the two commercial TiO2 materials, which present mixed phases (anatase/rutile), Degussa P25 (82%/18%) and Hombikat (76%/24%). 60% degradation was obtained using the laboratory-made pure anatase crystalline TiO2 phase. The pH and amount of catalyst showed minimum significant effect on the degradation efficiencies of DMP and DEP. Greater degradation efficiency was achieved using Degussa P25 at pH 10 with 1.5 g L−1 catalyst dosage. Under these conditions, complete degradation and 92% mineralization were achieved after 300 min of reaction. Additionally, a drastic decrease in the concentration of BOD5 and COD was observed, which results in significant enhancement of their biodegradability obtaining a BOD5/COD index of 0.66 after the photocatalytic treatment. The main intermediate products found were dimethyl 4-hydroxyphthalate, 4-hydroxy-diethyl phthalate, phthalic acid and phthalic anhydride indicating that the photocatalytic degradation pathway involved the hydrolysis reaction of the aliphatic chain and hydroxylation of the aromatic ring, obtaining products with lower toxicity than the initial molecules.

The preparation of hierarchical porous carbon sponges (HCS) from metal oxide nanoparticle@metal‐organic frameworks is reported. ZnO nanoparticles are partially converted to zeolitic imidazolate framework‐8 (ZIF‐8) crystals in presence of n‐butylamine to obtain ZnO@ZIF‐8 porous hybrids. After direct carbonization, followed by ZnO acidic etching, ZnO@ZIF‐8 crystals were converted to submicrometric HCS. Due to the high surface area and accessible porosity, combining micro‐ and mesoporosity of HCS, their application for the extraction of water pollutants was studied by preparing HCS/polymer membranes, and showed a high efficiency for the fast (650 L m−2 h−1) removal of plastic degradation by‐products (DBP, dibutyl phthalate. DEHP, bis(2‐n‐ethylhexyl)phthalate). DBP and DEHP breakthroughs were lower than 3 % after the filtration of 100 mL of water containing simultaneously both phthalates at a high concentration level (300 μg L−1, each). HCS/polymer membranes were reusable up to 5 times, maintaining their extraction capacity, with relative errors of 6 % for DBP, and

The sulfamethoxazole (SMX) mineralization through the solar photo electro-Fenton (SPEF) process in a pilot plant containing 20 L of 50 mg L−1 SMX solution was investigated. The process was carried out at pH 3 under different operational conditions varying temperature, volumetric flow and applied current density. Box-Behnken experimental design and response surface methodology (RSM) were used to optimize the experimental variables of the SPEF process. Under the optimal conditions, the SPEF was compared with electro-Fenton (EF) and anodic oxidation (AO- H2O2) processes. Under optimum design variables of 47 mA cm−2, 45 °C and 571 L h−1, SPEF was more efficient yielding 90% of TOC removal after 360 min of reaction with a maximum of 83% of mineralization current efficiency (MCE). The main by-products detected on the final solution treated by SPEF were oxalic, maleic, oxamic and fumaric acids, while NH4+ and NO3− were the main inorganic nitrogen ions released during the process.

In this study, samples of ZnO modified with copper (II) phthalocyanine (CuPc) (0.1% and 0.5% wt) were synthesized via the sol-gel method. The catalysts were characterized by DTA-TGA analysis, infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Ultraviolet diffuse reflectance spectroscopy (DRS-UV) was used to estimate the band gap energy (Eg) of the prepared materials, and the textural properties of the solids were determined from N2 adsorption isotherms. The photocatalytic activity of the ZnO-CuPc catalysts was evaluated on the degradation of the methylene blue (MB) and potassium cyanide (KCN) under UV and visible light. The dye concentration was determined spectrophotometrically at 665 nm during the treatment. The CN- content during the photocatalytic reaction was analyzed potentiometrically using a cyanide ion-selective electrode. Both pollutants were completely degraded under both light sources; however, the highest degradation rate was observed for MB decomposition achieving complete degradation in 150 min.

Nickel-doped TiO2 (0.1, 0.5, 1.0, 2.5, 5.0, and 10.0 wt%) photocatalysts were prepared by the sol–gel method. Physicochemical properties were determined by the characterization using X-ray diffraction, Raman and UV–vis diffuse reflectance spectroscopies, N2 physisorption, and zeta potential determination (PZC). The synthesized materials exhibited the photocatalytically active anatase crystalline phase and the catalysts exhibited stronger absorption in the visible light region with a red shift in the adsorption edge with the increase of Ni doping. The photocatalytic evaluation of TiO2−Ni materials was carried out on p-arsanilic acid (p-ASA, 10 mg L−1) degradation in aqueous suspension under visible radiation. Compared with bare TiO2, the TiO2–Ni 1.0 material (1 wt% Ni-doped TiO2) exhibited higher photocatalytic activity on p-ASA degradation under visible light irradiation allowing a 76% degradation percentage in 180 min reaction time while 60% degradation percentage was achieved with undoped TiO2. The TiO2–Ni 1.0 material showed the highest surface area in comparison with the other prepared materials. Meanwhile, the photocatalytic activity of TiO2–Ni 1.0 can keep even after three cycles with not loss of activity since nickel was not leached from the TiO2-based catalyst into the solution during photocatalytic reaction. Therefore, the doping of the nickel into the TiO2 lattice by the sol–gel method allowed its activation under visible radiation and an efficient photoexcited charge separation to prevent electron-hole recombination showing high chemical stability.

In this work, heterogeneous photocatalysis under visible light was applied as treatment to degrade bisphenol A (BPA) using Ni-TiO 2 catalysts with different Ni contents (0.5 and 1.0 wt%). The materials were synthesized by rapid microwave assisted sol-gel process (MW). For comparison, 1.0% Ni-TiO 2 by conventional sol-gel method (CM) was prepared. Semiconductors were characterized by various analytical techniques. Diffuse reflectance spectroscopy studies indicated a red shift in the band gap absorption to the visible region when nickel was incorporated while results from powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed the substitution of sites of Ti 4+ ions by Ni 2+ ions into the crystal lattice of anatase TiO 2 . The best results in BPA degradation were obtained at solution pH 9 in the follow order 1.0% Ni-TiO 2 MW > 0.5% Ni-TiO 2 MW > 1.0% Ni-TiO 2 CM > TiO 2 MW. This behavior was explained by the lower band gap (Eg) value, smaller crystallite size and the inhibition in recombination of the electron/hole pairs, caused by nickel incorporation. Using 1.0% Ni-TiO 2 MW as catalyst, complete BPA degradation, and 77% mineralization were achieved in 210 min. The toxicity of the final solution was also evaluated by means of the marine bacteria Vibrio fischeri .

In the present work, an alternative system of 5-hydroxymethylfurfural (HMF) oxidation was studied, in an effort to avoid the use of expensive precious metal catalysts, high pressures and systems not environmentally friendly. The catalysts tested were Co (II), Fe (II) and Cu (II) Salen complexes supported on SBA-15 (Co Salen/SBA-15, Fe Salen/SBA-15 and Cu Salen/SBA-15 respectively). The reaction was carried out in aqueous medium at room temperature (25 °C ± 1) and atmospheric pressure, using hydrogen peroxide (H 2 O 2 ) as the only oxidant agent. The effect of various reaction conditions such as H 2 O 2 content, oxidant agent amount, different transition metals present in the catalyst and temperature were evaluated. The HMF and the reaction products such as; 2,5-diformylfuran (DFF), 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and 5-formyl-2-furancarboxylic acid (FFCA) were followed by high performance liquid chromatography (HPLC) measurements. The selectivity and reaction kinetics under different reaction conditions was studied. The different synthesized catalysts were extensively characterized by UV–vis spectroscopy, subsequently by FTIR, DR-UV–vis, AA and XPS spectroscopy and through nitrogen physorption, which was related to its catalytic activity. The successful synthesis of SBA-15 support was confirmed by its textural properties and STEM. From the experimental data obtained a reaction mechanism with parallel reactions was proposed founding that the oxidation route of the alcohol group in HMF is favored over of the oxidation of the aldehyde group on the other side of the molecule.

The catalyst FeTiO3/ZnO was prepared by ultrasound-assisted chemical precipitation method. The material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDAX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). FeTiO3/ZnO (1, 5, and 10%wt. FeTiO3) was evaluated on photocatalytic degradation of ciprofloxacin (CPX) in an aqueous solution (10 mg L−1) under UV-Vis irradiation. The heterojunction between FeTiO3 and ZnO, the presence of Fe2O3 impurities, and the formation of oxygen vacancies allowed the coupled material FeTiO3/ZnO (1%wt.) showed a better photocatalytic performance (100% degradation CPX and 27% of mineralization) than bare ZnO. Although ZnO also attained complete degradation of CPX, the antibiotic was not mineralized under the same operating conditions. A scavenger study determined that h+ and OH were the principal reactive species involved in the CPX photocatalytic degradation. The heterostructured material showed high stability and reusability during three cycles of use.

In this work, BiOBr photocatalyst co-doped with Fe and N (Fe–BiOBr–N) was synthesized by a microwave-assisted solvothermal method. This material was characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, N2 adsorption-desorption, X-ray photoelectronic spectrometry, UV–Vis diffuse reflectance spectroscopy, atomic absorption spectroscopy, elemental analysis, and photoluminescence techniques. The characterization of this material revealed the formation of flower-like structures and the successful incorporation of Fe and N in BiOBr. The incorporation of Fe and N in BiOBr caused a decrease of the band gap (from 2.87 to 1.92 eV), the crystal size (from 12.93 to 8.43 nm), and the recombination rate of photogenerated charges compared with unmodified BiOBr. Likewise, these dopants caused an increase in specific surface area (from 7 to 16 m2/g). The photocatalytic activity was assessed on the elimination of bisphenol A (BPA) under visible radiation. Fe–BiOBr–N exhibited higher photocatalytic activity than pristine BiOBr on the BPA degradation, allowing complete degradation and 65% of mineralization in 240 min, while using pristine BiOBr 40% of degradation and 20% of mineralization were obtained. Fe–BiOBr–N is a promising option for the effective elimination of persistent contaminants such as BPA in the aqueous medium, under visible radiation.

In this research study, WO3/NaNbO3-coupled photocatalysts were synthesized at three WO3 mass ratios (15, 85, and 95 wt%) and characterized. These composites were characterized via X-ray powder diffraction, N2 physisorption, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and photoluminescence techniques. For comparison, bare WO3 and NaNbO3 were also synthesized and characterized. 2,4-Dichlorophenoxyacetic acid (2,4-D) was degraded under visible light to evaluate its photocatalytic performance. The WO3 (95 wt%)/NaNbO3 composite showed higher photocatalytic activity than pure WO3 and NaNbO3 and even than the 15 and 85 wt% coupled materials; thus, the combination with the highest ratio of WO3 with respect to NaNbO3 showed increased photocatalytic activity compared with the bare materials.

In this study, the photocatalytic removal of an emerging contaminant, diclofenac (DCF) sodium, was performed using the nitrogen-doped WO3/TiO2-coupled oxide catalyst (WO3/TiO2-N). The catalyst synthesis was accomplished by a sol–gel method using tetrabutyl orthotitanate (C16H36O4Ti), ammonium p-tungstate [(NH4)10H2W12O42·4H2O] and ammonium nitrate (NH4NO3) as the nitrogen source. For comparison, TiO2 and WO3/TiO2 were also prepared under similar conditions. Analysis by X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV–Vis spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the synthesized materials. The photocatalytic efficiency of the semiconductors was determined in a batch reactor irradiated with simulated solar light. Residual and mineralized DCF were quantified by high-performance liquid chromatography, total organic carbon analysis and ion exchange chromatography. The results indicated that the tungsten atoms were dispersed on the surface of TiO2 as WO3. The partial substitution of oxygen by nitrogen atoms into the lattice of TiO2 was an important factor to improve the photocatalytic efficiency of WO3/TiO2. Therefore, the best photocatalytic activity was obtained with the WO3/TiO2-N0.18 catalyst, reaching 100% DCF transformation at 250 kJ m−2 and complete mineralization at 400 kJ m−2 of solar-accumulated energy.

Photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in aqueous solution using Cr(III)-doped TiO2 under UV and visible light was investigated. The semiconductor material was synthesized by a microwave-assisted sol–gel method with Cr(III) doping contents of 0.02, 0.04, and 0.06 wt%. The catalyst was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption, UV–Vis diffuse reflectance spectroscopy (DRS), and atomic absorption spectroscopy (AAS). The photocatalytic activity for the photodegradation of MCPA was followed by reversed-phase high-performance liquid chromatography (HPLC) and total organic carbon (TOC) analysis. The intermediates formed during degradation were identified using gas chromatography–mass spectrometry (GC–MS). Chloride ion evolution was measured by ion chromatography. Characterization results showed that Cr(III)-doped TiO2 materials possessed a small crystalline size, high surface area, and mesoporous structure. UV–Vis DRS showed enhanced absorption in the visible region as a function of the Cr(III) concentration. The Cr(III)-doped TiO2 catalyst with 0.04 wt% of Cr(III) was more active than bare TiO2 for the degradation of MCPA under both UV and visible light. The intermediates identified during MCPA degradation were 4-chloro-2-methylphenol (CMP), 2-(4-hydroxy-2-methylphenoxy) acetic acid (HMPA), and 2-hydroxybuta-1,3-diene-1,4-diyl-bis (oxy)dimethanol (HBDM); the formation of these intermediates depended on the radiation source.

The improved photocatalyst carbon-doped WO 3 /TiO 2 mixed oxide was synthesized in this study using the sol–gel method. The catalyst was thoroughly characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy, N 2 adsorption desorption analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic efficiency of the prepared materials was evaluated with respect to the degradation of sodium diclofenac (DCF) in a batch reactor irradiated under simulated solar light. The progress of the degradation process of the drug was evaluated by high-performance liquid chromatography (HPLC), whereas mineralization was monitored by total organic carbon analysis (TOC) and ion chromatography (IC). The results of the photocatalytic evaluation indicated that the modified catalyst with tungsten and carbon (TWC) exhibited higher photocatalytic activity than TiO 2 (T) and WO 3 /TiO 2 (TW) in the degradation and mineralization of diclofenac (TWC>TW>T). Complete degradation of diclofenac occurred at 250 kJ m −2 of accumulated energy, whereas 82.4% mineralization at 400 kJ m −2 was achieved using the photocatalytic system WO 3 /TiO 2 -C. The improvement in the photocatalytic activity was attributed to the synergistic effect between carbon and WO 3 incorporated into the TiO 2 structure.

Phosphorous-doped Ti-Fe mixed oxide (P-TiO2-αFe2O3) catalysts were prepared by the microwave-assisted sol-gel route and characterized using XRD, SEM, N2 physisorption, UV–vis diffuse reflectance, FTIR, and XPS. P-TiO2-αFe2O3 was evaluated during the degradation of a sulfonamide mixture (5 mg/L, each) under visible light. The photocatalytic process was optimized with a face-centered central composite design. Under optimal conditions (0.5 wt% of αFe2O3, pH 10, and 0.75 g/L of catalyst loading), the sulfate radical advanced oxidation process was carried out using 5 mM K2S2O8 (PS). P doping shifted the light absorption of P-TiO2-αFe2O3 in the visible light range owing to substitutional doping, while the coupling of P-TiO2 with α-Fe2O3 enhanced the absorption in the visible range, which resulted in an increase in the lifetime of the charge carriers and in a superior photoactivity of the P-TiO2-αFe2O3 catalyst in comparison to that of TiO2. The mineralization yield of the sulfonamides (SNs) mixture was enhanced in the presence of an electron acceptor (SO4− ), allowing nearly 69 % within 300 min with the P-TiO2-αFe2O3/PS system, while P-TiO2-αFe2O3 and K2S2O8 oxidation achieved only 27 % and 21 %, respectively. The biodegradability index was 0.48 using the P-TiO2-αFe2O3/PS system, indicating a less toxic effluent than the original compounds. Recycling tests demonstrated that P-TiO2-αFe2O3 exhibits good stability in activating PS for SNs degradation during three cycles. Two main intermediates (pyrimidine and hydroquinone) and their hydroxylated re-arrangements were detected during the degradation of the SNs by the coupled process. Oxalic, oxamic, sulfonic, and acetic acids were also identified as by-products from the degradation of the SNs.

The photocatalytic degradation of a sodium diclofenac (DCF) solution (10 mg/L) under simulated solar radiation was evaluated using a ZnO semiconductor modified by the incorporation of 10, 15, and 20 wt.% fluorine (ZnO-F10, ZnO-F15 and ZnO-F20). The ZnO-F catalysts were synthesized by the sol-gel method using zinc acetate as a precursor of zinc oxide and NH4F as a fluorine source. The photocatalytic performance of the F-doped ZnO material was compared to that of bare ZnO. The obtained photocatalysts were characterized using X-ray diffraction (XRD), Scanning electron microscopy with Energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The Brunauer-Emmett-Teller (BET) surface area, pH of zero charge (pHpzc), and band gap of the solids were also evaluated. An experimental Box-Behnken design combined with response surface methodology was applied to establish the optimal conditions for the photocatalytic degradation of the DCF solution. Complete DCF degradation, total release of chloride ions, and approximately 90% mineralization were achieved during degradation of the drug at an accumulated energy of 400 kJ/m2 under the optimized experimental conditions (1 g/L of ZnO-F20 catalyst with the pH of the DCF solution maintained at 6.5).

An automated method for the analysis of methylparaben, propylparaben, benzophenone-3, and benzophenone-4 in water effluents via on-line solid-phase extraction coupled with high-performance liquid chromatography/ultraviolet detection was proposed. The preconcentration parameters were studied using Plackett-Burman and Box-Behnken experimental designs using a C18 sorbent material. The results demonstrated that the eluent volume, composition, and sorbent amount were statistically significant. Optimal conditions for these variables were an eluent volume of 1.55 mL, eluent composition of acetonitrile 100% v/v, and sorbent amount of 100 mg. The eluted sample was analyzed on-line using high-performance liquid chromatography equipped with a reversed-phase C18 column and ultraviolet detection. Separation of the analytes was achieved in 15 min using gradient elution with acetonitrile/water. A simple, sensitive, and rapid analytical method was proposed for personal care compounds without sophisticated or expensive equipment. The limits of detection were 1.20, 1.73, 2.51, and 4.67 μg/L for propylparaben, methylparaben, benzophenone-3, and benzophenone-4, respectively. The analysis time was 48 min, consuming only 1.59 mL of eluent acetonitrile for the solid phase extraction step, with minimal sample handling. The method was applied to the analysis of spiked swimming pool and wastewater, with recoveries between 65-107%. These results indicate the reliability of the flow-based procedure.

On-line sample pretreatment (clean-up and analyte preconcentration) was coupled to sequential injection chromatography for the determination of 2, 4-D (2,4-dichlorophenoxyacetic acid) and atrazine in corn samples. Prior to their analysis, microwave-assisted approach was evaluated and optimized for the extraction of 2,4-D and atrazine in corn samples. Extraction was carried out using MeOH:water (30:70 v/v) solvent at 50°C for 15 min. The on-line SPE-HPLC/UV approach combined reversed solid-phase extraction using strata X sorbent with MeOH:H2O (80:20 v/v) at 1 mL min-1 as eluent for the enrichment of the analytes. C18 monolithic column with acetonitrile:10 mM acetate buffer pH 4 (20:80, v/v) was employed as mobile phase at 2 mL min-1 flow rate for separation of the compounds before UV detection. Enrichment factors up to 13.4 were achieved with a 10 mL sample volume. The developed procedure showed linear response ranges from 0.07–0.70 mg kg−1 for 2,4-D and atrazine with correlation coefficients >0.993. The LODs were 0.03 and 0.02 mg kg-1 for 2,4-D and atrazine, respectively with RSD ranged from 4.0 to 7.2 % at 0.07 and 0.30 mg kg-1. The recoveries of 2,4-D and atrazine in corn samples were from 82.6 and 98.2%. The proposed method showed good recoveries and reasonable precision for herbicide analysis in corn samples avoiding the time-consuming batch sample pretreatment step, thus minimizing risks of sample contamination and analyte losses.

The Fe doped TiO2 catalyst was evaluated under visible radiation for As(III) removal. The TiO2–Fe was synthesized by sol–gel technique at 0.0, 1.0, 2.5, 5.0 and 10.0 wt% iron doping concentrations. The semiconductors were characterized by X-ray diffraction, diffuse reflectance UV–vis, Raman spectroscopy, nitrogen physisorption, SEM–EDS and potentiometric titration for point of zero charge determination. The photocatalytic oxidation of As(III) was assessed in aqueous suspension contained 5 mg L−1 As(III) at pH 7 with 0.25 g L−1 catalyst loading. The incorporation of iron ions in TiO2 lattice extended the absorption to visible light region and create surface oxygen vacancies which favor photocatalytic oxidation reaction of As(III) using a small doping amount of Fe (1.0 wt%) in TiO2 powder. Additionally, TiO2–Fe 1.0 showed the highest adsorption capacity for As(V) removal compared to sol–gel TiO2 and P25 indicating that this catalyst is a promising material for As contaminated groundwater treatment.

Cr3+-doped TiO2 nanoparticles (Ti-Cr) were synthesized by microwave-assisted sol-gel method. The Ti-Cr catalyst was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, N2 adsorption-desorption analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and zetametry. The anatase mesoporous Ti-Cr material exhibited a specific surface area of 54.5 m2/g. XPS analysis confirmed the proper substitution of Ti4+ cations by Cr3+ cations in the TiO2 matrix. The particle size was of average size of 17 nm for the undoped TiO2 but only 9.5 nm for Ti-Cr. The Cr atoms promoted the formation of hydroxyl radicals and modified the surface adsorptive properties of TiO2 due to the increase in surface acidity of the material. The photocatalytic evaluation demonstrated that the Ti-Cr catalyst completely degraded (4-chloro-2-methylphenoxy) acetic acid under visible light irradiation, while undoped TiO2 and P25 allowed 45.7% and 31.1%, respectively. The rate of degradation remained 52% after three cycles of catalyst reuse. The higher visible light photocatalytic activity of Ti-Cr was attributed to the beneficial effect of Cr3+ ions on the TiO2 surface creating defects within the TiO2 crystal lattice, which can act as charge-trapping sites, reducing the electron−hole recombination process.

A 3.0 L solar flow plant with a Pt/air-diffusion (anode/cathode) cell, a solar photoreactor and a photocatalytic photoreactor filled with TiO2-coated glass spheres has been utilized to couple solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) for treating a 165mgL(-1) salicylic acid solution of pH 3.0. Organics were destroyed by OH radicals formed on the TiO2 photocatalyst and at the Pt anode during water oxidation and in the bulk from Fenton's reaction between added Fe(2+) and cathodically generated H2O2, along with the photolytic action of sunlight. Poor salicylic acid removal and mineralization were attained using SPC, anodic oxidation with electrogenerated H2O2 (AO-H2O2) and coupled AO-H2O2-SPC. The electro-Fenton process accelerated the substrate decay, but with low mineralization by the formation of byproducts that are hardly destroyed by OH. The mineralization was strongly increased by SPEF due to the photolysis of products by sunlight, being enhanced by coupled SPEF-SPC due to the additional oxidation by OH at the TiO2 surface. The effect of current density on the performance of both processes was examined. The most potent SPEF-SPC process at 150mAcm(-2) yielded 87% mineralization and 13% current efficiency after consuming 6.0AhL(-1). Maleic, fumaric and oxalic acids detected as final carboxylic acids were completely removed by SPEF and SPEF-SPC.