Onion membrane: an efficient adsorbent for decoloring of wastewater

Background: recently, researchers have tried to design synthetic materials by replicating natural materials as anadsorbent for removing various types of environmental pollutants, which have reached to the risky levels in naturefor many countries in the world. in this research, the potential of onion membrane obtained from intermediate ofonion shells for adsorption of methylene blue (mb) as a model cationic dye was exhibited.methods: before and after adsorption, the membrane was characterized by fourier transform infrared spectroscopy(ftir) and optical and scanning electron microscopy in order to prove its dye adsorption capability. the variousexperimental conditions affecting dye adsorption were explored to achieve maximum adsorption capacity.results: the dye adsorption capacity of the membrane was found to be 1.055 g.g?1 with 84.45% efficiency afterone hour and 1.202 g.g?1 with 96.20% efficiency after eight hours in contact with the dye solution (0.3 g.l?1).moreover, the kinetic, thermodynamic and adsorption isotherm models were employed to described the mbadsorption processes. the results show that the data for adsorption of mb onto the membrane fitted well with thefreundlich isotherm and pseudo-second-order kinetic models. in addition, the mb adsorption from roomtemperature to ~50°c is spontaneous and thermodynamically favorable.conclusions: evidently, the high efficiency and fast removal of methylene blue using onion membrane suggest thesynthesis of polymer-based membranes with similar physical and chemical properties of onion membrane as avaluable and promising wastewater decoloring agents in water treatment.