A solid-phase extractant based on microemulsion modified date pits for toxic pollutants

Abstract

Application of microemulsion modified raw date pits as an inexpensive solid extractant for removing methylene blue (MB), copper ion (Cu2+) and cadmium ion (Cd2+) has been presented. The results summarised herein are also part of an investigation conducted to evaluate the adsorption capacity by taking into consideration the experimental parameters such as pH, particle size and initial solute concentration. The experimental data obtained from the adsorption isotherms studies were used to find pollutants distribution factors and modelled using both Langmuir and Freundlich equations. The modified adsorbent was more effective toward all pollutants with high removal capacities (50–350 mg/g) and with very large distribution values (9–235 L/g) which indicates the suitability of this new material for extraction organic and inorganic pollutants. After microemulsion modification, the FTIR scans of the samples show clear differences in the position and intensity the characteristics bands of the raw date pits (RDP). Three mechanisms of the MB, Cu2+ and Cd2+ adsorption onto μE-MDP are possible: (i) adsorption by an electrostatic force of the anionic head group of the surfactant and the positive charge of the dye (MB+) or the metal ions (Cu2+ or Cd2+), (ii) adsorption by tail groups of the surfactant and the hydrophobic character of the MB molecules. The MB is a basic dye and has basic characteristics and therefore is expected to interact strongly with the anionic head groups of the surfactants (RCOO–). In the contrary, the Cu2+ and Cd2+ ions are not expected to interact by the tail groups of the surfactant where the ionic radii of these ions may explain the differences between Cu2+ (0.72 Å) and Cd2+ (0.99 Å) adsorption capacities and (iii) filling the channel (pores) of the RDP by dissolving in the microemulsion micelles.