Treatment of As(V) and As(III) by electrocoagulation using Al and Fe electrode

Abstract

A batch electrocoagulation (EC) process with bipolar electrode and potentiodynamic polarization tests with monopolar systems were investigated as methods to explore the effects of electrode materials and initial solution pH on the As(V) and As(III) removal. The results displayed that the system with Al electrode has higher reaction rate during the initial period from 0 to 25 minutes than that of Fe electrode for alkaline condition. The pH increased with the EC time because the As(V) and As(III) removal by either co-precipitation or adsorption resulted in that the OH positions in Al-hydroxide or Fe-hydroxide were substituted by As(V) and As(III). The pH in Fe electrode system elevate higher than that in Al electrode because the As(V) removal substitutes more OH position in Fe-hydroxide than that in Al-hydroxide. EC system with Fe electrode can successfully remove the As(III) but system with Al electrode cannot because As(III) can strongly bind to the surface of Fe-hydroxide with forming inner-sphere species but weakly adsorb to the Al-hydroxide surface with forming outer-sphere species. The acidic solution can destroy the deposited hydroxide passive film then allow the metallic ions liberate into the solution, therefore, the acidic initial solution can enhance the As(V) and As(III) removal. The over potential calculation and potentiodynamic polarization tests reveal that the Fe electrode systems possess higher over potential and pitting potential than that of Al electrode system due to the fast hydrolysis of and the occurrence of Fe-hydroxide passive film.

Arsenite removal from groundwater by aerated electrocoagulation reactor with Al ball electrodes: Human health risk assessment

“…Also, As(III) attached to the Al-hydroxide via outer-sphere complex in which reaction H þ ion (Eq. ( 12)) was released (Kuan et al, 2009). Danilenko et al (2005) indicated that As(III) in EC process is partially oxidized to As(V) in the case of using Al anodes.…”

“…The sorbent surfaces such as amorphous Al(OH) 3 and Al 2 O 3 are positively charged up to pH 7 and at this pH, As(III) species (H 3 AsO 3 below pH 9.2, but H 2 AsO À 3 above pH 9.2) are uncharged and therefore cannot be bounded to the surface by electrostatic reaction. Sweep coagulation, in which interaction occurs between arsenic species and aluminium oxyhydroxide flocs such as Al(OH) 3 , AlO(OH) and Al 2 O 3 (Kuan et al, 2009;Hernandez, 2010).…”

“…As(III) in EC process can weakly adsorb to the Al-oxyhydroxide surfaces with forming outer-sphere species. As(III) is attached to the Al-hydroxide via outer-sphere complex and released H þ ion in the reaction (Kuan et al, 2009):…”

Isolation and characterization of arsenite oxidizing Pseudomonas lubricans and its potential use in bioremediation of wastewater

“…Conventional methods for removing metals from Industrial effluents include chemical precipitation, oxidation or reduction, ion exchange, filtration, electrochemical treatment, reverse osmosis, membrane technologies and evaporation recovery (Ahluwalia and Goyal, 2007;Kuan et al, 2009;Mouedhen et al, 2009). These processes may be ineffective or extremely expensive especially when the metals in solution are in the range of 1 -100 mg l -1 (Nourbakhsh et al, 1994).…”