Juliana Carla Garcia

Combined electrocoagulation and TiO2 photoassisted treatment applied to wastewater effluents from pharmaceutical and cosmetic industries.

The treated wastewater consists of refractory materials and high organic content of hydrolyzed peptone residues from pharmaceutical factory. The combination of electrocoagulation (EC) followed by heterogeneous photocatalysis (TiO(2)) conditions was maximized. The EC: iron cathode/anode (12.50 cmx2.50 cmx0.10 cm), current density 763Am(-2), 90min and initial pH 6.0. As EC consequence, the majority of the dissolved organic and suspended material was removed (about 91% and 86% of the turbidity and chemical oxygen demand (COD), respectively). After EC, refractory residues still remained in the effluent. The subsequent photocatalysis: UV/TiO(2)/H(2)O(2) (mercury lamps), pH 3.0, 4h irradiation, 0.25gL(-1) TiO(2) and 10mmolL(-1) H(2)O(2) shows high levels of inorganic and organic compounds eliminations. The obtained COD values: 1753mgL(-1) for the sample from the factory, 160mgL(-1) after EC and 50mgL(-1) after EC/photocatalyzed effluents pointed out that the combined treatment stresses this water purification.

The effect of operational parameters on electrocoagulation-flotation process followed by photocatalysis applied to the decontamination of water effluents from cellulose and paper factories.

Cellulose and paper pulp factories utilize a large amount of water generating several undesirable contaminants. The present work is a preliminary investigation that associates the electrocoagulation-flotation (EC) method followed by photocatalysis to treat such wastewater. For EC, the experiment with aluminium and iron electrodes showed similar efficiency. Iron electrodes (anode and cathode) were chosen. By applying 30min of EC/Fe(0), 153A m(-2) and pH 6.0, the COD values, UV-vis absorbance and turbidity underwent an intense decrease. For the subsequent UV photocatalysis (mercury lamps) TiO(2) was employed and the favourable operational conditions found were 0.25g L(-1) of the catalyst and solution pH 3.0. The addition of hydrogen peroxide (50mmol L(-1)) highly increased the photo-process performance. By employing the UV/TiO(2)/H(2)O(2) system, the COD reduction was 88% compared to pre-treated effluents and complete sample photobleaching was verified. The salt concentration on EC (iron electrodes) showed that the electrolysis duration can be reduced from 30 to 10min by the addition of 5.0g L(-1) of NaCl. The biodegradability index (BOD/COD) increased from 0.15 (pre-treated) to 0.48 (after EC) and to 0.89 (after EC/photocatalysis irradiated for 6h), showing that the employed sequence is very helpful to improve the water quality. This result was confirmed by biotoxicity tests performed with microcrustaceous Artemia salina.

Validation of the determination of fatty acids in milk by gas chromatography

Fatty acid methyl esters (FAMEs) in commercial milk samples were analyzed by gas chromatography coupled with flame ionization detection. The saturated fatty acids (SFA) were the most abundant. The major SFA were palmitic acid (16:0), estearic acid (18:0), and myristic acid (14:0). Significant differences (P 80%), indicating that the method can efficiently determine fatty acids in milk and dairy products.

Optimised photocatalytic degradation of a mixture of azo dyes using a TiO2/H2O2/UV process

The aim of the present study was to optimise the photocatalytic degradation of a mixture of six commercial azo dyes, by exposure to UV radiation in an aqueous solution containing TiO(2)-P25. Response surface methodology, based on a 3(2) full factorial experimental design with three replicates was employed for process optimisation with respect to two parameters: TiO(2) (0.1-0.9 g/L) and H(2)O(2) (1-100 mmol/L). The optimum conditions for photocatalytic degradation were achieved at concentrations of 0.5 g TiO(2)/L and 50 mmol H(2)O(2)/L, respectively. Dye mineralisation was confirmed by monitoring TOC, conductivity, sulfate and nitrate ions, with a sulfate ion yield of 96% under optimal reactor conditions. Complete decolorisation was attained after 240 min irradiation time for all tested azo-dyes, in a process which followed a pseudo-first kinetic order model, with a kinetic rate constant of approximately 0.018 min(-1). Based on these results, this photocatalytic process has promise as an alternative for the treatment of textile effluents.

Evolutive follow-up of the photocatalytic degradation of real textile effluents in TiO2 and TiO2/H2O2 systems and their toxic effects on Lactuca sativa seedlings

Textile industry wastes raise a great concern due to their strong coloration and toxicity. The objective of the present work was to characterize the degradation and mineralization of textile effluents by advanced oxidative processes using either TiO2 or TiO2/H2O2 association and to monitor the toxicity of the products formed during 6 h irradiation in relation to that of the in natura effluent. The results obtained demonstrated that the TiO2/H2O2 association was more efficient in the mineralization of textile effluents than TiO2 alone, with high mineralized ion concentrations (NH4+, NO3-, and SO42-) and significant organic matter reduction rates (represented by the COD and TOC). The toxicity of the degradation products to lettuce seeds (Lactuca sativa) was not significant, since percent germination was not significantly affected and neither was root and sprout percent growth. However, while the TiO2/H2O2 association was more toxic in the first hours of irradiation and less so in the end of the 6 h irradiation, the toxicity of TiO2 increased only slightly in the end of the experiments. Comparatively, the photogenerated products of both the TiO2 and the TiO2/H2O2 association were less toxic than the in natura effluent.

Review of Utilization Plant-Based Coagulants as Alternatives to Textile Wastewater Treatment

With the increased demand for textile products, the textile industry and its wastewaters have been increasing proportionally, making it one of the main sources of severe pollution problems worldwide. Textile wastewater treatment is one the most difficult environmental problems because it contains high color, biochemical oxygen demand (BOD), chemical oxygen demand (COD), pH, temperature, turbidity and toxic chemicals. The direct discharge of this wastewater without previous or proper treatment into the water bodies, like lakes, rivers, etc. pollutes the water affecting directly and indirectly the water. Coagulation/flocculation is one of the most widely used for wastewater treatment, as it is efficient and simple to operate. This process is used for the removal of suspended and dissolved solids, colloids and organic matter present in industrial wastewater. Natural coagulants have been attracting wide interest of researchers because they have the advantages of biodegradability, safe for human health, environmental friendly, generally toxic free and produce no secondary pollution. These coagulants are extracted from natural and renewable sources, such as microorganisms, animals or plants. Not only this, the sludge volume generated by the natural coagulants is smaller than chemical coagulants; it can further be treated biologically or can be disposed safely as soil conditioners because of their non-toxicity. The raw plant extracts are often available locally and hence, a low-cost alternative to chemical coagulants. In recent years, numerous studies on natural coagulants are growing and there is an urgent need to establish the use of natural low-cost coagulants for textile wastewater treatment. In this chapter, we show the characteristics of dyes and textile wastewater, emphasizing adverse impacts on environmental and human health and we mentioned some technologies for the textile wastewater treatment, highlighting the CF, since it is efficient, is easy to operate and is commonly used at the industries. We also have been discussed the physical-chemical concept of CF as well the major mechanisms involved at process. The usage of plant-based natural coagulants as alternative to chemical coagulants in the textile wastewater treatment is the goal of this chapter.

Study of biodiesel photodegradation through reactions catalyzed by Fenton's reagent

This study reports on the photodegradation of biodiesel in contact with water using the photo-Fenton reaction. After 360 h of photodegradation, we observed a reduction of 73% in the amount of fatty acid methyl esters (FAMEs) initially quantified by gas chromatography coupled with a flame ionization detector (GC/FID). During the photodegradation, peaks for ketones and epoxy groups in carbon chains were recorded by gas chromatography coupled with mass spectrometry (GC/MS), and typical aldehyde and short-chain fatty acid shifts in hydrogen nuclear magnetic resonance spectroscopy (1H NMR) were observed. Ecotoxicity assays with Artemia salina revealed the presence of toxic components in the aqueous phase in increasing amounts up to 168 h of photodegradation and decreasing thereafter.

Optimization of photocatalytic degradation of biodiesel using TiO2/H2O2 by experimental design

This study reports on the investigation of the photodegradation of biodiesel (B100) in contact with water using TiO2/H2O2. The TiO2 was characterized by X-ray diffraction analysis (XRD), pH point of zero charge (pHpzc) and textural analysis. The results of the experiments were fitted to a quadratic polynomial model developed using response surface methodology (RSM) to optimize the parameters. Using the three factors, three levels, and the Box-Behnken design of experiment technique, 15 sets of experiments were designed considering the effective ranges of the influential parameters. The responses of those parameters were optimized using computational techniques. After 24h of irradiation under an Hg vapor lamp, removal of 22.0% of the oils and greases (OG) and a 33.54% reduction in the total of fatty acid methyl ester (FAME) concentration was observed in the aqueous phase, as determined using gas chromatography coupled with flame ionization detection (GC/FID). The estimate of FAMEs undergo base-catalyzed hydrolysis is at least 3years (1095days) and after photocatalytic treatment using TiO2/H2O2, it was reduced to 33.54% of FAMEs in only 1day.

Hydrogen peroxide-assisted photocatalytic degradation of textile wastewater using titanium dioxide and zinc oxide

ABSTRACT The present work investigated the degradation of a dyeing factory effluent by advanced oxidative process under UV irradiation. TiO2 and ZnO were used as catalysts and the influence of different concentrations of H2O2 added to the system was studied. The catalysts were characterized in terms of crystal structure (X-ray diffraction), textural properties (Brunauer–Emmett–Teller area and pore volume) and point of zero charge, which indicated the semiconductors had a positively charged surface in an acidic medium. After 8 h of irradiation at pH 3.0 and catalyst concentration of 0.0625 g L−1, the effect of H2O2 was evaluated by means of kinetic efficiency (rate constants), absorbance reduction (at 284, 621 e 669 nm), total organic carbon reduction and mineralization (in terms of the formation of ions such as and ). Adding H2O2 to the photocatalytic system significantly increased pollutants’ removal, highlighting tests with 1.0 × 10−2 mol L−1, showing higher absorbance reduction and rate constants at 621 and 669 nm for TiO2 and best mineralization rates for ZnO. Ecotoxicity bioassays using Artemia salina L confirmed the treatment efficacy, with effluent lethal concentration (LC50) increasing from 65.68% (in natura) to over 100% after photocatalysis treatment.