Pre-concentration by natural adsorbent as plausible tool for effective electro-Fenton removal of micropollutants

摘要

Nowadays, the vast majority of pollutants are found at low concentrations in water bodies and their treatment requires efficient and cost-effective strategies. This research proposes the application of two complementary treatments (physical and oxidative) for the removal of the ionic liquid 1-butyl, 2,3-dimethylimidazolium chloride ([bdmim]Cl) from aqueous medium. Initially, a quick adsorption process was set up. For that, a natural silicate, attapulgite, was used as adsorbent and an uptake of 7.3 mg g(-1) was attained. Once the viability of the adsorbent was proved, a continuous adsorption treatment, using a column, was carried out and the behaviour of the proposed system was studied using theoretical and experimental breakthrough models. Afterwards, the regeneration of the adsorbent was evaluated with different desorbing agents reaching the best results with a mixture 20/80 H2O/ACN with 0.04 M NH4Cl. Five adsorption-desorption cycles were done using the attapulgite as adsorbent without any detriment on the process performance, opening a path for future applications. After the desorption of the pollutant and the ACN recuperation, an extremely concentrated aqueous solution of the pollutant was attained (618 mg L-1 of [bdmin]Cl and 0.2 M NH4Cl) and treated by electro-Fenton process. NH4Cl showed a high detrimental effect on the electro-Fenton (EF) process and thus, it was removed. Then, the new solution was efficiently treated by EF with a low energy consumption (0.05 kWh g TOC-1) and high mineralization levels (70%) after 8 h of treatment.