Abstract
This work studied the removal of phenol from industrial effluents through catalytic ozonation in the presence of granular activated carbon in a continuous fixed-bed reactor. Phenol was chosen as model pollutant because of its environmental impact and high toxicity. Based on the evolution of total organic carbon (TOC) and phenol concentration, a kinetic model was proposed to study the effect of the operational variables on the combined adsorption–oxidation (Ad/Ox) process. The proposed three-phase model expressed the oxidation phenomena in the liquid and the adsorption and oxidation on the surface of the granular activated carbon in the form of two kinetic constants, k1 and k2 respectively. The interpretation of the constants allow to study the benefits and behaviour of the use of activated carbon during the ozonisation process under different conditions affecting adsorption, oxidation, and mass transfer. Additionally, the calculated kinetic parameters helped to explain the observed changes in treatment efficiency. The results showed that phenol would be completely removed at an effective contact time of 3.71 min, operating at an alkaline pH of 11.0 and an ozone gas concentration of 19.0 mg L−1. Under these conditions, a 97.0% decrease in the initial total organic carbon was observed.
Highlights
Increases in the world population and the industrial revolution have brought many advantages to humanity
In order to study the influence of granular activated carbons (GAC) on phenol removal, a preliminary experiment was performed with ozone alone in a fixed-bed reactor, with an inert material and adsorption or ozonation only in the presence of GAC, in order to evaluate the improvement achieved by activated carbon
This low degradation could be due to the oxidation potential of ozone being lower (E◦ = 2.07 V) than that of the hydroxyl radicals (E◦ = 2.80 V) generated by the indirect reactions associated with the decomposition of ozone in the presence of GAC [22]
Summary
Increases in the world population and the industrial revolution have brought many advantages to humanity. The intensive use and pollution of natural resources is leading many developed countries on the European and American continents towards an ecological deficit by the first third of the 21st century [1] For this reason, national governments are encouraging the improvement of manufacturing production processes to increase the efficiency of water resources, as well as raw materials, in order to minimise the environmental impact of goods produced. To safeguard the environment and public health, it is necessary the development and implementation of effective wastewater treatment that allow us to exceed the quality standards regulated by the U.S Environmental Protection Agency’s (EPA) Water Quality Standards Regulation (WQSR) [3] or the Water Framework Directive (Directive 2000/60/EC) of the European Union [4]. In 2015, the United Nations (UN) included SDG 6 on Clean
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