Development of novel composite from chitosan/iron oxide nanoparticle/laterite for the reduction of arsenic and synthetic dye from water

Abstract

Contaminants in surface and ground water has been a cause of serious concerns across the globe, especially for Bangladesh. Surface water is being heavily polluted by industrial discharges as well as improper use of fertilizers and pesticides resulting in the accumulation of heavy metals and carcinogenic dyes in water. The removal of contaminants from wastewater has always been a challenging task and researchers have been trying to develop improved biomaterial based adsorbents as they are biodegradable and have little associated cost in production. Due to the abundant availability of shrimp waste and laterite soil, a novel composite has been proposed in this study that is synthesized from chitosan, laterite and iron oxide nanoparticles. The composite was prepared with a view to producing a low cost, biodegradable and biocompatible material. Laterite and iron oxide nanoparticles were added to the chitosan-acetic acid solution followed by thorough mixing of the components. In the process, sodium tri-polyphosphate was used as the crosslinking agent. The removal efficiency of the composite was tested by investigating its adsorption capacity of methylene blue and arsenic in batch process. To recover the composite after adsorption, iron oxide nanoparticles were integrated so that they can be collected from the solution utilizing magnetic property. The composite was characterized using fourier-transform infrared spectroscopy, x-ray diffractometer, energy-dispersive x-ray spectroscopy, scanning and transmission electron microscopes to study chemical and the morphological changes that occurred during the composite synthesis. The results showed that the removal efficiency of contaminants was higher compared to some other composites. The removal of methylene blue dye was fast and depends heavily on the solution pH. At high pH range (11-12), the dye adsorption occurs rapidly with a maximum removal efficiency. However, the arsenic adsorption shows the opposite trend with maximum removal occurring at pH around 3. Other factors such as initial concentration, adsorbent dosage were also measured to examine their effects on adsorption. Equilibrium adsorption capacity was measured and maximum adsorption capacity was found to be 14.18 mg/g for methylene blue and 0.306 mg/g for arsenic (V). Both adsorption behaviors followed closely to Langmuir isotherm model. The adsorption rate kinetics showed well fitted to pseudo second order for both the contaminants.