Purification of Industrial Wastewater from Methylene Blue (MB) Dye Using Organic and Inorganic Sol–gel Glasses

Abstract

Organic and inorganic-doped sol-gel glasses have been synthesized via thermal followed by microwave treatment. Tetramethoxysilane (TMEOS) was used as a precursor, whereas dopants used were Neodymium oxide, Urea (carbamide) or Thiourea (thiocarbamide) and the obtained formulations werereferred as Nd, U, and THU, respectively along with the undoped or plain glass (P). Colors of the as-prepared sol-gel glasses ranged from transparent colorless (P) to opaque dark purple (Nd). The latter colorcould be owed to the presence of the inorganic transition element oxide (Nd2O3).In addition, THU had the smallest particle size range (< 250 microns), whereas the other three sol-gel glasses had larger particle sizes ranging from 250- 630 microns.Thesynthesized sol-gel glasses were tested for their capacity to adsorb and remove Methylene Blue (MB) dye from aqueous solutions. Uexhibited the highestsorptioncapacitiesof 12.6 and 2.6 mg/g with removal efficiencies of 50.3 % and 83.2 %at 12 and 2 mg/L MB, respectively.These values were almost twice and 1.7 times those obtained by P at the higher and lower MB concentrations, respectively which indicates that doping with urea enhanced sorption through introducing new functional groups.Fourier transform Infrared (FTIR)spectroscopy revealed that carbonyl group on urea could be responsible for adsorption via electrostatic interaction between the negatively charged carbonyl oxygen of urea and the positively charged nitrogen or sulfur on MB, or through redox reactions between them.