title: Spectroscopic study of Se(IV) removal from water by reductive precipitation using sulfide.
abstract: This study investigates the removal of selenium (IV) from water by reductive precipitation using sodium sulfide at neutral pH. Also, it examines the application of UV light as an activating method to enhance reductive precipitation. Furthermore, this work evaluates the effects of sulfide dose and solution pH on behavior of Se(IV) reduction. Selenium was effectively removed in sulfide solution at both neutral and acidic pH. UV irradiation did not enhance removal efficiency of Se(IV) at conditions tested, but it affected solids morphology and composition. SEM/EDS and XPS results showed that selenite was reduced to elemental Se or Se-S precipitates (e.g. SenS8-n) in sulfide solution. High resolution S 2p XPS spectra suggested the presence of sulfur-containing anions (e.g. S2O3(2-), HSO3(-), etc.) or elemental S (S(0)), monosulfide (S(2-)), and polysulfides (Sn(2-)), which could be produced from sulfide photolysis or reaction with Se. In addition, large aggregates of irregular shape, which suggest Se-S precipitates or elemental sulfur, were found more prominently at pH 4 than at pH 7, and they were more noticeable in the presence of UV with longer reaction times. In addition, XRD patterns showed that gray elemental Se solids were dominant in experiments without UV, whereas Se-S precipitates (Se3S5) with an orange color were found in those with UV.
authors.affiliation: Chemical Engineering Program, Texas A&M University at Qatar, PO BOX 23874, Doha, Qatar. Electronic address: bahngmi.jung@qatar.tamu.edu.
authors.forename: Bahngmi
authors.initials: B
authors.lastname: Jung
authors.affiliation: Chemical Engineering Program, Texas A&M University at Qatar, PO BOX 23874, Doha, Qatar.
authors.forename: Aya
authors.initials: A
authors.lastname: Safan
authors.affiliation: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
authors.forename: Bill
authors.initials: B
authors.lastname: Batchelor
authors.affiliation: Chemical Engineering Program, Texas A&M University at Qatar, PO BOX 23874, Doha, Qatar; Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA. Electronic address: ahmed.abdel-wahab@qatar.tamu.edu.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Abdel-Wahab
mesh_terms: D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010782:Photolysis; D012643:Selenium / Q000032:analysis* / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry; D012996:Solutions; D013057:Spectrum Analysis; D013440:Sulfides / Q000032:analysis / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D018036:Selenium Compounds; D012996:Solutions; D013440:Sulfides; D014874:Water Pollutants, Chemical; D014867:Water; D013455:Sulfur; C032915:polysulfide; D012643:Selenium; C033479:sodium sulfide
keywords: Reductive precipitation; Selenite; Selenium removal; Sodium sulfide; Ultraviolet light