PROMOTION OF PHOTO-INDUCED BASED GREEN TECHNOLOGIES FOR WATER TREATMENT WITH PESTICIDES CONTENT

Project PN II – Program 4 – Partnerships in prioritised areas.

AREA OF RESEARCH – Environment

CONTRACT – 32131/01.10.2008

PERIOD: 2008 – 2011

CONSORTIUM

National Research and Development Institute for Industrial Ecology-INCD ECOIND – Coordinator

UNIVERSITY of Bucharest- Research Center for Applied Physical-Chemistry – CC CFTA  – Partner

POLYTECHNIC UNIVERSITY BUCHAREST- Applied   Inorganic Chemistry Section  – Partner

S.C. SECOM  S.A. – Partner

GENERAL  OBJECTIVE

Developmant of a technology for advanced degradation of pesticides   (maximum admitted concentrations <0.1 µg/L) from  water applying an advanced photo catalytic oxidation process, using sunlight as UV-VIS irradiance source, associated with  iron based catalyst separation by flotation and its valorization in the degradation process.

SPECIFIC OBJECTIVES

• Establishment of database regarding  the mechanisms, kinetics, performance of Fenton, photo-Fenton advanced oxidation processes on pesticides degradation and the flotation process applied for catalyst recovery;
• Definition of contaminated sites with various classes of pesticides by identifying their concentration domaines and associated pollution matrices of different water sources;
• Developing an integrated technology for both advanced degradation of pesticides, that will allows treated effluent quality complying with stringent rules imposed by national and European legislation (<0.1µg/L) in terms of pesticides content and iron separation in order to its capitalization;
• Dissemination and transfer of project results to demonstrate the functionality of the proposed treatment technology and finding potential beneficiaries.

ELEMENTS OF NOVELTY

• Ecological and modern treatment process, not approached  at national level until now;
• Use of natural source of UV-VIS radiation – sunlight;
• Minimization of waste generated from the water treatment process by valorization of iron based photo-catalyst

RESULTS / INDICATORS

• Databese establish in the frame of homogenous Fenton and photo-Fenton processes applicability in the degradation of various classes of pesticides (triazines, organochlorine, organophosphorus, carbamic) in terms of mechanisms, kinetics of pollutants degradation and the influence of operating parameters (pH, H₂O₂ concentration, Fe²⁺ concentration, pollutant concentration) on the process efficiency;

• Literature study on the separation of iron from aqueous solutions by ion flotation emphasizing the basic phenomena involved in the separation process and the influence of operating parameters on the process efficiency.

• Pesticide pollution evaluation of different water sources (industrial effluents, natural receivers);
• Evaluation of the operating parameters influence on lindane removal has revealed the positive effect of Fenton reagent concentration increasing and extended reaction time on the efficiency of pesticide degradation; even in strong operation conditions, classic Fenton process application does not assures the level of residual pesticide concentrations below the limit for surface water discharge; the disadvantage can be overcome by replacing the conventional process with the photo-Fenton one;

• Performance of photo-Fenton process is higher than Fenton classic, even when reducing the concentration of H₂O₂ and Fe²⁺, confirming the important role of  hydrocomplex Fe(OH)²⁺ reduction under UV-VIS irradiance, in • OH  radicals generating, with positive effect on pollutant degradation (η ≥ 99.94%);
• Application of photo-Fenton process leads to lindane degradation and mineralization of organic chlorine by pseudo-first order kinetics, with maximum values of rate constants higher than those recorded in the case of classical Fenton process;
• Lindane degradation mechanism in UV-VIS/H₂O₂/Fe^{2 +}system is based on •OH radical attack on the pollutant by extraction of H atom with formation of chlorinated aromatic intermediates (trichlorobenzene, hexachlorobenzene) which are turned of into corresponding hydroxo derivates; these intermediates are oxidized to C₁-C₆ carboxylic acids and even CO₂ and H₂O;
• Lindane oxidation effectiveness calculation in photo-Fenton process demonstrates process efficiency in terms of energy consumption;

• Fe^{3 +}separation from post-photo-Fenton oxidation effluent is performed in the folloing system :pH correction- collector(sodium oleate-NaOL) dosing -flotation;
• Unitary flow developed for the treatment of water containing lindan by advanced oxidation – flotation process includes:

–        Wastewater treatment line with the following sequence of operations: pretreatment by settling (optional applied), UV-VIS/H₂O₂/Fe^{2 +} advanced oxidation – Fe^{3 +}precipitation- flotation;

–        Line of Fe^{3 +}recovery (as FeCl₃) applying the following operations: centrifugation-acid solubilisation. The product obtained can be capitalized as photocatalysts in the advanced oxidation treatment phase or as coagulant for other water treatment processes.

For each proposed stages / operations the operating parameters and the consumptions of reagents were set in order to assures advanced degradation of lindane from wastewater (tens µg/L) and Fe^{3 +}separation, with the compliance of treated effluent quality with the limits for discharging into surface waters (lindane ≤ 0.02 µg/L, Σ HCH ≤ 0.042 µg/L, Fe <2 mg/L).

Dissemination of results through:

– Dedicated workshop Organizing;

– Presentation of 3 papers in scientific events with international participation;

– Publication of three articles in ISI papers.

Fig.1. Solar- photo catalytic plant (photo reactor, sun tracking system)

Fig.2. Degradation of HCH   isomers through solar-Fenton process. Influence of irradiation time on the residual concentrations of pollutants

THE MAIN BENEFICIARIES / USERS

• SMEs, active in pesticides synthesis / conditioning;
• Units of Central and Local Administration;
• Environmental Protection Agencies and water utilities
• R & D units that are interested or active in environmental protection research