Arsenic (III) oxidation of water applying a combination of hydrogen peroxide and UVC radiation

Abstract

Arsenic is toxic to both plants and animals and inorganic arsenicals are proven carcinogens in humans. The oxidation of As(III) to As(v) is desirable for enhancing the immobilization of arsenic and is required for most arsenic removal technologies. The main objective of this research is to apply an Advanced Oxidation Process that combines ultraviolet radiation and hydrogen peroxide (UVC/H(2)O(2)) for oxidizing aqueous solutions of As(III). For that purpose, a discontinuous photochemical reactor (laboratory scale) was built with two 40 W tubular germicidal lamps (λ = 253.7 nm) operating inside a recycling system. The study was made beginning with a concentration of 200 μg L(-1) of As(III), changing the H(2)O(2) concentration and the spectral fluence rate on the reactor windows. Based on references in the literature on the photolysis of hydrogen peroxide, arsenic oxidation and our experimental results, a complete reaction scheme, apt for reaction kinetics mathematical modelling, is proposed. In addition, the effectiveness of arsenic oxidation was evaluated using a raw groundwater sample. It is concluded that the photochemical treatment of As(III) using H(2)O(2) and UVC radiation is a simple and feasible technique for the oxidation of As(III) to As(v).

Arsenic removal from water employing a combined system: photooxidation and adsorption

“…Prior to the As (III) determination, a speciation process was performed employing solid phase extraction (SPE) in order to separate As (III) and As (V) species. The technique was applied and detailed in a previous work (Lescano et al 2011). Thus, the concentration of As (V) was calculated from the difference between the As (III) concentration at time t and As (III) initial concentration (measured at t=0).…”

“…The dosage of hydrogen peroxide employed for all the experiences were adopted according to a previous work, which includes the study of the optimal H 2 O 2 concentration for this process (Lescano et al 2011). Each experiment was repeated two times.…”

“…Taking into account the oxidation process previously studied (Lescano et al 2011) and the experiences performed by mini fixed column assays (Lescano 2013), an adsorption column is designed in order to be connected to the annular reactor above described. The dimensions of the column and the employed flow rate were calculated from the empty bed residence time (EBRT) and the bed volume desired.…”

“…They were designed taking into account the oxidation process previously 4.8 mg L −1 Total arsenic (As) 50 μg L −1 Fig. 1 Photography of the reactor studied (Lescano et al 2011) and the experiences performed by mini fixed column assays (Lescano 2013). More details can be found in the "Adsorption column" section.…”

“…According to the literature found, the UV/H 2 O 2 is the least AOPs studied to transform As (III) into As (V) and can be suitable to apply when pollutants are in low concentrations, such as arsenic, since in this case, it is not necessary to use high concentrations of hydrogen peroxide. Due to this fact, first of all, the authors have been studying the efficiency and kinetics of the UV/H 2 O 2 process for arsenic oxidation (Lescano et al 2011(Lescano et al , 2012. Then, the adsorption process was studied because of its simple operation and relative low cost for arsenic removal.…”