Effectiveness of Cupressus sempervirens cones as biosorbent for the removal of basic dyes from aqueous solutions in batch and dynamic modes.

The feasibility of using cypress cone chips from Cupressus sempervirens as a low-cost biosorbent for the removal of two representative basic dyes, methylene blue (MB) and rhodamine B (RhB), from aqueous solutions was investigated in batch and continuous modes. Dyes biosorption was strongly dependent on the solution's pH. Sorption kinetics was determined and properly described by the pseudo-second-order rate model. Experimental equilibrium isotherms fitted the Langmuir model, showing maximum biosorption capacities of 0.62 mmol/g for MB and 0.24 mmol/g for RhB. Competitive experiments from a binary solution of the dyes demonstrated the preference of the cone chips for biosorbing MB. Very low desorption efficiencies were obtained for both dyes. Dynamic experiments showed that the breakthrough time was three times higher for MB biosorption than for RhB for the same conditions. Breakthrough curves were properly represented by a mathematical model.