ADSORPTION OF ARSENIC (V) FROM AQUEOUS SOLUTIONS BY GOETHITE-COATED SILICA NANOPARTICLES

Silica nanoparticles were synthesized and modified by coating the nanoparticles with goethite for the removal of arsenic (V) from aqueous solutions. We used scanning electron microscopy (SEM), fourier transformed infrared spectrometry (FT-IR) and zetasizer to characterize particle size, surface morphology, functional groups and surface charge of the synthesized and modified nanoparticles. Scanning Electron Microscopy results showed that the size of the synthesized silica nanoparticles ranged from 100-150 nm. Batch sorption studies were carried out on the adsorption of arsenic (V) as a function of pH, contact time, initial concentration, temperature and ionic strength. The results showed that maximum adsorption occurred at pH 3.0. Kinetics study revealed that adsorption of arsenic (V) by goethite-coated silica nanoparticles was rapid and equilibrium was reached in 120 min. The maximum adsorption capacity of the goethite-coated silica nanoparticles for arsenic (V) from Langmuir isotherm was 32.40 mg/g. The adsorbent had high efficiency in removing arsenic from aqueous solutions, even at low initial concentrations. The adsorption data was analyzed by both Langmuir and Freundlich isotherm models. The presence of phosphorous reduced the adsorption of arsenic on to goethite-coated silica nanoparticles.