Kinetics of dodecylbenzenesulphonate mineralisation by TiO2 photocatalysis

In this work, the kinetics of mineralisation of sodium dodecylbenzenesulphonate (DBS) by TiO2 photocatalysis has been studied. Although several works have studied the kinetics of photodegradation of the primary pollutant, the formation of organic intermediates brings a worse situation when those compounds are hardly oxidised. Total mineralisation is thus the desired objective in any oxidation process, being the kinetics a good indicator of the process efficacy. Working between 50 mg L−1 and 200 mg L−1 of DBS and catalyst loadings between 0.5 g L−1 and 5 g L−1, the mineralisation kinetics of DBS degradation by TiO2 photocatalysis has been experimentally and theoretically analysed. The mineralisation kinetic curves presented two different zones with different slopes, the second one attributed to the intermediate compounds and with a lower rate. Data in the two zones fitted to second order kinetic models with different values of the kinetic parameters. Additionally, the kinetics of DBS removal has also been analysed observing that kinetic data corresponding to high surfactant concentration followed a second order trend similar to the mineralisation results.