| The high-efficiency and ecofrienfly adsorbent can be prepared by chemical modification of Walnut Shell due to Walnut shell contains large amounts of cellulose and lignin. In this study, the samples of acrylic acid modified Walnut Shell (AA-WNS) and acrylic acid modified NaOH-treated Walnut Shell (MWNS) were prepared by using acrylic acid as monomer and potassium permanganate as initiator.The optimal synthesis conditions obtained by single factor tests is as follow:initiator concentration is 16mmol·L-1, initiation time is 30min, acrylic monomer concentration is 1.08mmol·L-1, reaction temperature is 69℃, reaction time is 90min, the graft yield of AA-WNS is up to 19.02%. The sample of AA-WNS was characterized by FTIR, XPS, SEM and EDS. The effects of graft yield, adsorbent dose, pH, contact time and temperature on the adsorption of Pb2+were studied by static adsorption experiments.The adsorption equilibrium and kinetics of the removal of Pb2+ from aqueous solution by AA-WNS and MWNS was investigated in the temperature range of 288-308 K. The adsorption kinetic data were well correlated by pseudo-second-order model. The adsorption isotherm data were better interpreted by Langmuir isotherm model, and the maximum adsorption capacity of AA-WNS and MWNS for Pb2+ was 203.65mg·g-1 and 238.65mg·g-1 at 308 K. The adsorption rates of AA-WNS and MWNS were mainly governed by film diffusion. The thermodynamic parameters (ΔG, ΔH and ΔS) showed that the adsorption process to be spontaneous, endothermic in nature. The recycling property of AA-WNS and MWNS were studied, and the results showed that there were not apparent loss in equilibrium adsorption capacities during four adsorption times, and adsorption capacities for AA-WNS and MWNS were larger than 89%. |
PDF Full Text Request