Porous magnetic resin-g-chitosan beads for adsorptive removal of phenolic compounds.

In this study, porous magnetic resin grafted chitosan (R-g-Ch) beads were prepared for removal of 4-chlorophenol and phenol from aqueous solutions. The R-g-Ch beads were characterized by vibrating sample magnetometer, Fourier-transform infrared spectroscopy, scanning electron microscopy and thermogravimetry methods. The removal of the phenolic compounds was optimized by varying the experimental conditions. Results herein are well fitted to the pseudo-second order kinetic and Langmuir isotherm. The maximum adsorption capacity of phenol and 4-chlorophenol were found to be 188.6 and 99 mg/g, respectively. The thermodynamic studies suggested that the adsorption process was exothermic, irreversible and feasible within the range of 298-318 K.

Onion membrane: an efficient adsorbent for decoloring of wastewater.

BACKGROUND: Recently, researchers have tried to design synthetic materials by replicating natural materials as an adsorbent for removing various types of environmental pollutants, which have reached to the risky levels in nature for many countries in the world. In this research, the potential of onion membrane obtained from intermediate of onion 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 various experimental 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 after one 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 MB adsorption processes. The results show that the data for adsorption of MB onto the membrane fitted well with the Freundlich isotherm and pseudo-second-order kinetic models. In addition, the MB adsorption from room temperature to ~50°C is spontaneous and thermodynamically favorable. CONCLUSIONS: Evidently, the high efficiency and fast removal of methylene blue using onion membrane suggest the synthesis of polymer-based membranes with similar physical and chemical properties of onion membrane as a valuable and promising wastewater decoloring agents in water treatment.