Complete Removal of Organoarsenic by the UV/Permanganate Process via HO^• Oxidation and in Situ-Formed Manganese Dioxide Adsorption

Abstract

The UV/permanganate process is an innovative advanced oxidation process (AOP) that generates oxidative species, such as hydroxyl radicals (HO • ) and reactive manganese species (RMnS), and adsorptive species of in situ formed MnO 2 . The cooperation of oxidation and adsorption has the potential to remove organic metals from water. Herein, the removal of organoarsenic compounds of roxarsone and p-arsanilic acid by UV/permanganate was investigated. The pseudo-first-order reaction rate (k ox ′) of roxarsone was 0.0375 min −1 at a permanganate dose of 100 μM and pH 7.0 in the UV/ permanganate process, which was mainly attributable to HO • . The transformation of roxarsone was initiated with a HO • attack on the C−As bond, releasing As(V), which was then removed from the aqueous phase by MnO 2 adsorption. Additionally, hydroxylated products were generated by HO • oxidation and subsequently oxidized into nitro-1,4-benzoquinone and ring cleavage products. Under neutral conditions, the removal rate of total arsenic reached 73% at 20 min, 50% of roxarsone was transferred to As(V) via oxidation, and the in situ formed MnO 2 could remove 78% of the remaining roxarsone and 70% of As(V) via adsorption. With an increase in the pH from 3.0 to 9.0, the k ox ′ of oxidation decreased by 68%, whereas the removal rate of total arsenic increased from just 20% to 73%. This is the first study to use the UV/permanganate process to completely remove organic heavy metals with the combination of oxidative and adsorptive species, which demonstrates that this process is promising in water treatment.

Efficient Inactivation and Removal of a Harmful Marine Algae—Heterosigma akashiwo—By UV-Assisted Permanganate Oxidation

“…The UV/KMnO 4 process is known as an emerging technology that can enhance the oxidation of micropollutants and organic metals by producing hydroxyl radicals (•OH) and active manganese species (RMnS) [18,19]. As documented previously, •OH shows great efficiency in inactivating algal cells [20,21].…”

The removal of Cd(ii) by the UV/permanganate process: role of continuously in situ formed MnO2 and reactive species

“…6,7 Simultaneously, manganese dioxide (MnO 2 ) is formed in situ as the final product of permanganate reduction, 4,[8][9][10][11][12] which is environmentally friendly and readily removed through sedimentationfiltration process. 13 Compared with commercial and natural MnO 2 , the in situ formed MnO 2 generated via permanganate reduction exists as nano-sized MnO 2 colloids with higher specific surface areas, resulting in better adsorption capacity towards pollutants in water. [14][15][16] Nano-sized MnO 2 is reported to efficiently adsorb heavy metals in water such as Cd(II), Cu(II), Pb(II) and Tl(I) 12,17 with higher adsorption enthalpy compared with Al 2 O 3 and Fe 2 O 3 .…”

“…Recently, the UV/permanganate advanced oxidation process (AOP) has been reported to show a great performance in oxidizing organic heavy metals and organic pollutants by producing hydroxyl radicals (HO˙) and reactive manganese species (RMnS). 13,24,25 Meanwhile, the formation of in situ formed MnO 2 with nano sizes of 50-60 nm is considerable via UV irradiation. 24 After destroying the C-As bond of roxarsone by HO˙, the released negatively charged inorganic arsenic can be adsorbed by the in situ formed MnO 2 with a removal percentage of 73.0%.…”

“…24 After destroying the C-As bond of roxarsone by HO˙, the released negatively charged inorganic arsenic can be adsorbed by the in situ formed MnO 2 with a removal percentage of 73.0%. 13 Since the typical heavy metal ions are positively charged, their removal by the negatively charged in situ formed MnO 2 (ref. 19) should be more efficient than the inorganic arsenic.…”

Manipulating Excitonic Effects in Layered Bismuth Oxyhalides for Photocatalysis

“…The expansion of the world’s population and unrestrained industrial growth in the past few decades have escalated the consumption of fossil fuels (coal, petroleum, natural gas), as well as the unabated release of greenhouse gas (CO 2 ). − According to a report from Earth System Research Laboratories, the CO 2 content in the atmosphere in 2019 was much beyond preindustrial levels, which has intensified global warming and caused anomalous climate change. Meanwhile, a vast number of environmentally harmful pollutants and toxins (NO x , SO x , organic pollutants) arising from fossil fuel combustion are discharged into the air and water bodies, posing a danger to the ecosystem and contributing to pollution-related diseases. − To ensure global sustainability, developing environmentally benign and energy-efficient technologies to decrease the CO 2 concentration and eliminate environmental pollutants should therefore be our goal.…”