Enhanced removal of hazardous dye form aqueous solutions and real textile wastewater using bifunctional chitin/lignin biosorbent

A new biomaterial based on chitin and lignin was prepared and applied for the removal of hazardous dye C.I. Direct Blue 71 (DB71) from aqueous solutions and wastewaters. The dye sorption on the chitin/lignin biosorbent (Ch/L) was examined depending on the initial dye concentration (50-200 mg/L), phase contact time (1-1440 min), kind of auxiliaries (NaCl, Na2SO4, anionic surfactant SDS) and their concentrations (1-20 g/L salts, 0.1-0.75 g/L SDS), initial solution pH as well as temperature (20-50 °C). The equilibrium and kinetic characteristics of C.I. Direct Blue 71 uptake by chitin/lignin followed by the Freundlich isotherm model and the pseudo-second order model rather than the Langmuir, Tempkin models, and pseudo-first order model. C.I. Direct Blue 71 adsorption on chitin/lignin was spontaneous (−2.86 to −8.14 kJ/mol) and endothermic (60.1 kJ/mol). The possibilities of dye elution and reuse by means of the batch method were investigated and as follows the chemical reaction is an inseparable sorption mechanism. Purification of wastewaters containing direct dyes was made with 91% efficiency after 1 h of phase contact time. For comparison, data obtained or obtained results in the DB71-chitin (Ch) system were also presented.