Study of Reactive Red 195 anionic dye adsorption on calcined marble powder as potential eco-friendly adsorbent

Recently, use of inexpensive and available adsorbents have been studied for removal purposes. One of main sources of environmental pollutions is uncontrolled discharge of wastewater containing synthetic dyes that may result in adverse effect on human health. At this study, removal efficiency of marble powder (MP) and calcined marble powder (CMP) as potential and low cost natural adsorbents for removal of Reactive Red 195 as anionic dye was investigated.

The adsorbents were characterized by X-Ray diffraction, Fourier Transform Infrared spectroscopy, scanning electron microscopy and zeta potential measurements. Anionic dye of Reactive Red 195 was used as adsorbate. Raw MP was collected from marble processing plant and its calcination was done at 750°C for 3 h in furnace.

Effect of variables including pH, adsorbent dose, contact time, dye concentration and temperature were studied by a batch system. Adsorption reactions at equilibrium followed Langmuir isotherm and pseudo-second order kinetic models. Maximum adsorption capacity of 103.092 mg g-1 was observed for CMP that was more than MP (1.218 mg g-1). Results showed that calcination process can significantly reduce negative charges on surface of marble powder and promote its efficiency for anionic dye removal. Thermodynamic study revealed that adsorption of Reactive Red 195 on CMP was exothermic and spontaneously. In conclusion, abundance of MP as inorganic waste and its transformation to CMP by simple calcination process makes it an efficient, available and economic candidate for water purification.