title: TiO2/Ag modified penta-bismuth hepta-oxide nitrate and its adsorption performance for azo dye removal.
abstract: A modified hydrophilic penta-bismuth hepta-oxide nitrate (Bi5O7NO3) surface was synthesized via a precipitation method using TiO2 and Ag as modified agents. The synthesized product was characterized by different analytical techniques. The removal efficiency was evaluated using mono- and di-sulphonated azo dyes as model pollutants. Different kinetic, isotherm and diffusion models were chosen to describe the adsorption process. X-ray photoelectron spectroscopy (XPS) results revealed no noticeable differences in the chemical states of modified adsorbent when compared to pure Bi5O7NO3; however, the presence of hydrophilic centres such as TiO2 and Ag developed positively charged surface groups and improved its adsorption performance to a wide range of azo dyes. Dyes removal was found to be a function of adsorbent dosage, initial dye concentration, solution pH and temperature. The reduction of Langmuir 1,2-mixed order kinetics to the second or first-order kinetics could be successfully used to describe the adsorption of dyes onto the modified adsorbent. Mass transfer can be described by intra-particle diffusion at a certain stage, but it was not the rate limiting step that controlled the adsorption process. Homogenous behavior of adsorbent surface can be explored by applying Langmuir isotherm to fit the adsorption data.
authors.affiliation: Advanced Material and Nanotechnology Laboratory, Institute ofAdvanced Technology, Universiti Putra Malaysia, 43400, UPM Serdang, Selangor, Malaysia. yemenahmed2009@gmail.com
authors.forename: Eshraq Ahmed
authors.initials: EA
authors.lastname: Abdullah
authors.forename: Abdul Halim
authors.initials: AH
authors.lastname: Abdullah
authors.forename: Zulkarnain
authors.initials: Z
authors.lastname: Zainal
authors.forename: Mohd Zobir
authors.initials: MZ
authors.lastname: Hussein
authors.forename: Tan Kar
authors.initials: TK
authors.lastname: Ban
mesh_terms: D000327:Adsorption; D001391:Azo Compounds / Q000737:chemistry*; D001729:Bismuth / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D012834:Silver; D013818:Thermogravimetry; D013997:Time Factors; D014025:Titanium; D014865:Waste Disposal, Fluid / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D009566:Nitrates; C573451:penta-bismuth hepta-oxide nitrate; C009495:titanium dioxide; D012834:Silver; D014025:Titanium; D001729:Bismuth