Kinetic study of food dyes removal from aqueous solutions by solar heterogeneous photocatalysis with artificial neural networks and phytotoxicity assessment

Abstract

a b s t r a c tEffluent treatment for food industry wastewater is a subject of growing concern among the scientific community. Synthetic dyes are a major case and their presence can disturb aquatic environments and introduce highly toxic potentials to the ecosystem, even at low concentrations. In this study, the chemical kinetics of a degradation process was studied for the treatment of a Tartrazine (E102) and Brilliant Blue (E133) solution by different methods. First, the efficiency of eight advanced oxidative processes systems was investigated in their treatment. The most efficient result was obtained in a UV-solar/H 2 O 2 /TiO 2 system, which reached a degradation percentage of 99.36% in 180 min. Second, a 2 3 factorial planning was used to enhance quantitative degradation in this system and a similar result (99.21%) was reached in 90 min with the optimal conditions. The kinetics of this experiment was fitted in a pseudo-first-order model and the rate constant (k) estimated as 0.0541 min -1 . An artificial neural network was developed for the experiment to describe the degradation behaviour over time with a minimum error. Chemical oxygen demand and conductivity were estimated in order to assure the environmental quality of the samples. A Lactuca sativa bioassay revealed an upturn in LC 50 , the concentration to inhibit 50% of the organism growth, from 39.31% (v/v) to 87.73% (v/v). The result indicates a highly favourable reduction in acute phytotoxicity, that coupled with quantitative efficiency, makes the proposed use of solar light as radiation source and improvements in water quality parameters a suitable tool for large-scale synthetic dye treatment.

New aluminum mesh from recyclable material for immobilization of TiO2 in heterogeneous photocatalysis

“…No significant degradation was achieved in any of the experiments in the dark since the free radicals are not effectively formed in the absence of radiation. Do Nascimento Júnior et al [3] and Wang et al [53] found similar results for synthetic food dyes degradation applying TiO 2 photocatalysis. The direct photolysis systems did not present adequate results because the synthetic dyes are known to be stable to light.…”

“…A pseudo‐first‐order kinetic model was fitted to the degradation data for both systems. Previous reports in the literature have shown that advanced oxidation processes based on UV radiation absorption tend to follow a first‐order reaction kinetic profile . Kinetic rate constants (k/min −1 ) and half‐life reaction times (t 1/2 /min) were estimated by the modelling.…”

“…Previous reports in the literature have shown that advanced oxidation processes based on UV radiation absorption tend to follow a first-order reaction kinetic profile. [3,7] Kinetic rate constants (k/min −1 ) and half-life reaction times (t 1/2 / min) were estimated by the modelling. Five cycles were performed for 5 hours each in the batch reactor.…”

“…In addition to microorganisms, fat, sugar, and a variety of macromolecules, synthetic dyes are frequent pollutants in food industry wastewater . They are favoured in industrial processes due to their stability to light and oxygen and for granting homogenous colouration to products . The problem arises when they reach natural waters, causing several adverse effects such as bioaccumulation, toxic effects to fauna and flora, decrease of light penetration and oxygen dissolution, and inhibition in photosynthesis …”

“…[1,2] They are favoured in industrial processes due to their stability to light and oxygen and for granting homogenous colouration to products. [3] The problem arises when they reach natural waters, causing several adverse effects such as bioaccumulation, toxic effects to fauna and flora, decrease of light penetration and oxygen dissolution, and inhibition in photosynthesis. [4][5][6] Synthetic dyes, such as other emerging contaminants, are normally resistant to the conventional water treatment due to their stability properties and require alternative technologies for their elimination from water bodies.…”