Biosorption of Rhodamine 6G from aqueous solutions onto almond shell (Prunus dulcis) as a low cost biosorbent

This work presents an alternative methodology for removal of a dyestuff, Rhodamine 6G (R6G), from aqueous solutions by using a new biosorbent, almond shell (Prunus dulcis), in a batch biosorption technique. The characterization of the biosorbent was performed by using FTIR and SEM techniques. The biosorption characteristics of R6G onto almond shell (AS) was investigated with respect to the changes in initial pH of dye solutions, contact time, initial R6G concentration, AS concentration, temperature etc. The influences of ionic strength on the biosorption process were also investigated. The biosorption kinetics was followed by pseudo-second-order model for all investigated initial R6G concentrations. Experimental data showed a good fit with both the Langmuir and Freundlich isotherm models. The monolayer biosorption capacity of AS was found to be 32.6 mg g− 1 by using Langmuir model equations. Thermodynamic parameters including the Gibbs free energy (∆Gº), enthalpy (∆Hº), and entropy (∆Sº) changes indicated that the biosorption of R6G onto AS was feasible, spontaneous and endothermic in the temperature range of 0–40 °C.