Removal of arsenic from water using synthetic Fe sub(7)S sub(8) nanoparticles

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2016-04, Vol.290, p.428-437
• Main Authors: Cantu, Jesus, Gonzalez, Louis E, Goodship, Jacqueline, Contreras, Monica, Joseph, Meera, Garza, Cameron, Eubanks, T M, Parsons, J G
• Format: Article
• Language: English
• Subjects: Adsorption; Binding; Mathematical analysis; Micrographs; Nanostructure; Sorption; Spontaneous
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2016.01.053

In the present study, pyrrhotite was used to remove arsenite and arsenate from aqueous solutions. The Fe sub(7)S sub(8) was synthesized using a solvothermal synthetic method and it was characterized using XRD and SEM micrographs. Furthermore, the particle size for the nanomaterial Fe sub(7)S sub(8) was determined to be 29.86 plus or minus 0.87 nm using Scherer's equation. During the pH profile studies, the optimum pH for the binding of As(III) and As(V) was determined to be pH 4. Batch isotherm studies were performed to determine the binding capacity of As(III) and As(V), which was determined to be 14.3 mg/g and 31.3 mg/g, respectively for 25 degree C. The thermodynamic studies indicated that the Delta G for the sorption of As(III) and As(V) ranged from -115.5 kJ/mol to -0.96 kJ/mol, indicating a spontaneous process was occurring. The enthalpy indicated that an exothermic reaction was occurring during the adsorption in which the Delta H was -53.69 kJ/mol and -32.51 kJ/mol for As(III) and As(V), respectively. In addition, Delta S values for the reaction had negative values of -160.46 J/K and -99.77 J/K for the adsorption of As(III) and As(V), respectively which indicated that the reaction was spontaneous at low temperatures. Furthermore, the sorption for As(III) and As(V) was determined to follow the second order kinetics adsorption model.