Application of Fe(Ⅵ)in abating contaminants in water:State of art and knowledge gaps

The past two decades have witnessed the rapid development and wide application of Fe(Ⅵ)in the field of water de-contamination because of its environmentally benign character.Fe(Ⅵ)has been mainly applied as a highly efficient oxidant/disinfectant for the selective elimination of contaminants.The in situ generated iron(III)(hydr)oxides with the function of adsorption/coagulation can further increase the removal of contaminants by Fe(Ⅵ)in some cases.Because of the limitations of Fe(Ⅵ)per se,various modified methods have been developed to improve the performance of Fe(Ⅵ)oxidation technology.Based on the published literature,this paper summarized the current views on the intrinsic properties of Fe(Ⅵ)with the emphasis on the self-decay mechanism of Fe(Ⅵ).The applications of Fe(Ⅵ)as a sole oxidant for decomposing organic contaminants rich in electron-donating moieties,as a bi-functional reagent(both oxidant and coagulant)for eliminating some special contaminants,and as a disinfectant for inactivating microorganisms were systematically summarized.Moreover,the difficulties in synthesizing and preserving Fe(Ⅵ),which limits the large-scale application of Fe(Ⅵ),and the potential formation of toxic byproducts during Fe(Ⅵ)application were presented.This paper also systematically reviewed the important nodes in developing methods to improve the performance of Fe(Ⅵ)as oxidant or disinfectant in the past two decades,and proposed the future research needs for the development of Fe(Ⅵ)technologies.

The performance and mechanism of iron-mediated chemical oxidation:Advances in hydrogen peroxide,persulfate and percarbonate oxidation

Many studies have successfully built iron-mediatedmaterials to activate or catalyze Fentonlike reactions,with applications in water and wastewater treatment being investigated.However,the developed materials are rarely compared with each other regarding their performance of organic contaminant removal.In this review,the recent advances of Fentonlike processes in homogeneous and heterogeneous ways are summarized,especially the performance and mechanism of activators including ferrous iron,zero valent iron,iron oxides,iron-loaded carbon,zeolite,and metal organic framework materials.Also,this work mainly compares three O-O bond containing oxidants including hydrogen dioxide,persulfate,and percarbonate,which are environmental-friendly oxidants and feasible for in-situ chemical oxidation.The influence of reaction conditions,catalyst properties and benefits are analyzed and compared.In addition,the challenges and strategies of these oxidants in applications and the major mechanisms of the oxidation process have been discussed.This work can help understand the mechanistic insights of variable Fenton-like reactions,the role of emerging iron-based materials,and provide guidance for choosing appropriate technologies when facing real-world water and wastewater applications.

The effectiveness of bisulfite-activated permanganate technology to enhance the coagulation efficiency of Microcystis aeruginosa

The effects of bisulfite-activated permanganate technology(PM/BS)as a pre-oxidation process on enhancing Microcystis aeruginosa(M.aeruginosa)removal by post coagulation were investigated.The results demonstrated that pretreatment with PM/BS process effectively promoted the algae removal by coagulation with Al2(SO4)3 as the coagulant and this phenomenon was more obvious with the increase of water hardness.Compared to the sole coagulation,PM/BS pre-oxidation combing with coagulation could neutralize the zeta potential of algal cells effectively,decrease the algal cell size,and lead to the formation of more compact flocs due to the in-situ generated Mn02.The effect of oxidant dosages on algal organic matter(AOM)was also studied and no obvious release of macromolecular substances was observed with the dosage of KMn04 increasing from 3.0 mg/L to 7.0 mg/L,suggesting the integrity of algal cells at a high KMn04 dosage.Moreover,PM/BS pre-oxidation could lead to the decrease of most analyzed disinfection by-products(DBPs)at a Al2(SO4)3 dosage of 40.0 mg/L.The algae removal efficiency was also significantly enhanced by PM/BS pre-oxidation in the test using real algae-laden water.This study indicated that PM/BS process might be a potential assistant technology for algae removal by subsequent coagulation.