Photochemical UV/TiO2 treatment of olive mill wastewater (OMW)

Olive mill wastewater (OMW) was treated by photocatalysis using TiO2 under UV irradiation on the laboratory scale. The chemical oxygen demand, the coloration at 330 nm, and the level of phenols all showed decreases which, after a 24-h treatment, reached 22%, 57% and 94%, respectively. The differences between these three values indicate the persistence of colourless, non-phenolic compounds. Application of the novel Fictitious Atomic-Group Separation method showed an increase in carbon oxidation state and confirmed that the attack primarily concerns, aromatic moieties. A fine spectroscopic study revealed the occurrence of three successive phases during the degradation process, thought to correspond to three different categories of molecules in the OMW and the presence of pectin compounds

Effect of cations Ca2+ and Mg2+ on the removal efficiency of humic acid by UV/TiO2

زمینه و هدف: اسید هیومیک (HA) از تجزیه عناصر گیاهی و حیوانی آزاد می شود. مواد هیومیکی به عنوان پیش ساز محصولات جانبی گندزدایی در فرآیند کلرزنی نقش دارند. هدف از مطالعه حاضر بررسی اثر کاتیون های Ca2+،Mg2+ بر کارآیی حذف اسید هیومیک توسط UV/TiO2 بود. روش بررسی: در این مطالعه نیمه تجربی تأثیر پارامترهای pH، زمان تماس، غلظت دی اکسید تیتانیوم (TiO2)، غلظت Ca2+و غلظت Mg2+بر میزان حذف اسید هیومیک با استفاده از روش UV/TiO2 بر روی آب سنتتیک و آب خام زاینده رود اصفهان بررسی شد. یافته ها: غلظت بهینه کاتالیست نانو ذره دی اکسید تیتانیوم جهت حذف اسید هیومیک g/L1 بدست آمد. تحت شرایط اسیدی (3pH=) در زمان تماس 60 دقیقه بالاترین راندمان حذف به دست آمد. کارآیی حذف HA به روش UV/TiO2 با افزایش زمان تماس کاهش یافت. در حضور یون های Ca2+ و Mg2+ میزان حذف HA به روش UV/TiO2 افزایش یافت. نتیجه گیری: فرآیند فتوکاتالیستی نانو ذره دی اکسید تیتانیوم منجر به کاهش قابل ملاحظه ای از مواد هیومیکی موجود در آب می شود. اگر آب یا فاضلاب حاوی میزان بالایی از ترکیبات مقاوم و سختی باشند، می توان با یک تصفیه فتوکاتالیتیکی مقدماتی این ترکیبات را شکسته و به محصولات جانبی قابل تجزیه تغییر شکل داد

Evaluation of a TiO2 photocatalysis treatment on nitrophenols and nitramines contaminated plant wastewaters by solid-phase extraction coupled with ESI HPLC–MS

Nitration reactions of aromatic compounds are commonly involved in different industrial processes for pharmaceutical, pesticide or military uses. For many years, most of the manufacturing sites used lagooning systems to treat their process effluents. In view of a photocatalytic degradation assay, the wastewater of a lagoon was investigated by using HPLC coupled with mass spectrometry. The wastewater was highly concentrated in RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro- 1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and two herbicides Dinoterb (2-tert-butyl-4,6-dinitrophenol) and Dinoseb (2-sec-butyl-4,6-dinitrophenol). First of all, an analytical method using solid-phase extraction (SPE) combined with HPLC ESI MS/MS was put in work for identification and titration of RDX, HMX and the two dinitrophenols in a complex natural matrix. Then, the UV/TiO2 treatment was investigated for pollutants removal. Dinitrophenolic compoundswere significantly degraded after a 8-h-exposition of the wastewater/TiO2 suspension, whereas RDX and HMX were poorly affected

Kinetic study of adsorption and photo-decolorization of Reactive Red 198 on TiO2 surface

Recycling and reuse of wastewater after purification will reduce the environmental pollution as well as fulfill the increasing demand of water. Adsorption-based water treatment process is very popular for dye-house wastewater treatment. The present study deals with treatment of wastewater contaminated by reactive dye. TiO2 is used as adsorbent and the spent adsorbent has been regenerated by Advanced Oxidation Process (AOP), without using any other chemicals. TiO2 adsorbs dye molecules and then those dye molecules have been oxidized via a photocatalytic reaction in presence of UV irradiation. Kinetics of dye adsorption and photocatalytic oxidation reaction has been developed in this study. Photocatalyst adsorbent (TiO2) has been reused several times after regeneration. The activity of catalyst decreases after each cycle; due to poisoning cause by intermediate by-products. Kinetic of this catalyst deactivation has been incorporated with L–H model to develop the photocatalytic reaction kinetic model

Wastewater Treatment by Advanced Oxidation Process and Their Worldwide Research Trends

Background: Water is a scarce resource and is considered a fundamental pillar of sustainable development. The modern development of society requires more and more drinking water. For this cleaner wastewater, treatments are key factors. Among those that exist, advanced oxidation processes are being researched as one of the sustainable solutions. The main objective of this manuscript is to show the scientific advances in this field. Methods: In this paper, a systematic analysis of all the existing scientific works was carried out to verify the evolution of this line of research. Results: It was observed that the three main countries researching this field are China, Spain, and the USA. Regarding the scientific collaboration between countries, three clusters were detected—one of Spain, one of China and the USA, and one of Italy and France. The publications are grouped around three types of water: industrial, urban, and drinking. Regarding the research, 15 clusters identified from the keywords analyzed the advanced oxidation process (alone or combined with biological oxidation) with the type of wastewater and the target pollutant, removal of which is intended. Finally, the most important scientific communities or clusters detected in terms of the number of published articles were those related to the elimination of pollutants of biological origin, such as bacteria, and of industrial nature, such as pesticides or pharmaceutical products

UV/TiO2 photocatalytic degradation of xanthene dyes

UV/titanium dioxide (TiO2) degradation of two xanthene dyes, erythrosine B (Ery) and eosin Y (Eos), was studied in a photocatalytic reactor. Photocatalysis was able to degrade 98% of Ery and 73% of Eos and led to 65% of chemical oxygen demand removal. Experiments in buffered solutions at different initial pH values reveal the pH dependence of the process, with better results obtained under acidic conditions due to the electrostatic attraction caused by the opposite charges of TiO2 (positive) and of anionic dyes (negative). Batch activity tests under methanogenic conditions showed the high toxicity exerted by the dyes even at low concentrations (~85% with initial concentration of 0.3 mmol L 1), but the end products of photocatalytic treatment were much less toxic toward methanogenic bacteria, as detoxification of 85 ± 5% for Eos and 64 ± 7% for Ery were obtained. In contrast, the dyes had no inhibitory effect on the biogeniccarbon biodegradation activity of aerobic biomass, obtained by respirometry. The results demonstrate that photocatalysis combining UV/TiO2 as a pretreatment followed by an anaerobic biological process may be promising for the treatment of wastewaters produced by many industries.This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS UEFISCDI, project PN-II-ID-PCE-2011-3-0559, contract 265/2011, and the PTDC/AMB/69335/2006 project grants. Luciana Pereira holds a Pos-Doc fellowship (SFRH/BPD/80941/2011), Raquel Pereira holds a fellowship (SFRH/BPD/39086/2007) and Catarina S. Oliveira holds a PhD fellowship (SFRH/BD/32289/2006) from Fundacao para a Ciencia e Tecnologia

Degrading Endocrine Disrupting Chemicals fromWastewater by TiO2 Photocatalysis: A Review

Widespread concerns continue to be raised about the impacts of exposure to chemical compounds with endocrine disrupting activities. To date, the percolation of endocrine disrupting chemical (EDC) effluent into the aquatic system remains an intricate challenge abroad the nations. With the innovation of advanced oxidation processes (AOPs), there has been a consistent growing interest in this research field. Hence, the aim of this paper is to focus one such method within the AOPs, namely, heterogeneous photocatalysis and how it is used on the abatement of EDCs, phthalates, bisphenol A and chlorophenols in particular, using TiO2-based catalysts. Degradation mechanisms, pathways, and intermediate products of various EDCs for TiO2 photocatalysis are described in detail. The effect of key operational parameters on TiO2 photocatalytic degradation of various EDCs is then specifically covered. Finally, the future prospects together with the challenges for the TiO2 photocatalysis on EDCs degradation are summarized and discussed

Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a $^{60}$Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO$_2$ was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments.Comment: 25 pages, 7 figure

UV/Tio2 photocatalytic reactor for real textile wastewaters treatment

Textile dye wastewaters are characterized by strong colour, salts and other additives, high pH, temperature, chemical oxygen demand (COD) and biodegradable materials. Being aesthetically and environmentally unacceptable, these wastewaters need to be treated before their discharge. Anaerobic bioprocesses have been proposed as being environmentally friendly and relatively cheap; however, when applied to real effluent with a complex composition, they can fail. In this study, a photoreactor combining UV light and TiO2, immobilized in cellulosic fabric, was applied for the treatment of two industrial textile wastewaters. High colour and COD removal, and detoxification, were achieved for both wastewaters, at controlled pH of 5.5. Effluents showed very poor biodegradability due to their complex composition; thus, the proposed process is an efficient alternative