equilibrium and kinetic studies of direct red 81 biosorption onto modified silk maze as an economical biosorbent

in this study, the potential of biosorbent obtained from silk maze, was investigated for the batch biosorption of direct red 81 (dr 81) in aqueous solution. the effects of temperature, biosorbent amount, contact time, initial dye concentration and ultrasonic irradiation were also evaluated. furthermore, experimental equilibrium and kinetics data were fitted by langmuir and freundlich isotherms and pseudo-first-order and pseudo-second-order kinetic models, respectively. kinetic experiments revealed that the biosorption of dr 81 onto modified silk maze can be described with a pseudo second-order model while the equilibrium isotherm data were well described by the freundlich model. the negative thermodynamic values of δh o and δg o showed that the biosorption is an endothermic process and occurs spontaneously in the nature.the results presented that this waste material may be a suitable biosorbent for removal of industrial effluents due to its low cost and high efficiency.