Selective separation of Light green and Safranin O from aqueous solution using Salvadora persica (Miswak) powder as a new biosorbent

In this paper a novel solid phase extraction method to remove Light green (acid dye) and Safranin O (basic dye) using Salvadora persica (Miswak) powder as a new biosorbent is described. The adsorption conditions such as contact time, initial dye concentration, pH and temperature were studied by using batch system. After optimization, Miswak showed an excellent removal rate for dyes, the extraction of the dyes was accomplished in a period range of 1-10 min. The adsorption kinetics data were in good agreement with the pseudo-second-order rate model (R2 = 0.98) and the initial sorption rate (h) was found to be 0.01 g mmol−1 min−1. The new adsorbent was found to have a maximum adsorption capacity of 17.3 mmol/g. The adsorption isotherms could be adequately described by the Freundlich equation (R2 = 0.91) and the 1/n value is 0.9, which attributed to the heterogeneous surface structure of the Miswak. Study of the variation of the sorption of the tested dyes with temperature yielded values for ΔH, ΔS, and ΔG of −21.0, −0.056.3 and −4.2 kJ mol−1, respectively.