Study On The Adsorption Of Chromium (Ⅵ) In Wastewater By Peanut Shell

It is very expensive and ineffective to remove metalions from wastewaters using conventional methods when the initial concentration is low(＜100 mg/l).The use of adsorption is becoming research hot spot in recent years due to its low cost and convenient.It studies the static adsorption function of peanut shell over hexavalent chromium from simulative wastewater.in this paper.Peanut shell is a kind of agriculture waste with large quantities in our country. Making full use of their low heavy metal adsorption cost,we can get rid of the pollutant with those wastes without causing seond-time pollution.In this paper,the effects on Cr(Ⅵ) adsorption of pH,temperature,Cr(Ⅵ) initial concentration, dosage,time,ionic strength were studied.The equilibrium data were fitted into the Langmuir and the Freundlich isotherm models and the correlated coefficients were gained from the models.From the aspect of adsorptive kinetics,this paper also describes adosption behaviors of peanut shell on Cr(Ⅵ).The experimental result indicates the following:(1) pH value is the main factor affecting the adsorption effects.Increasing the adsorbent dosage,temperature and prolonging adsorb time within some extent can improve adsorption capacity,however,its influence on adsorption effects is relatively smaller.Common coexisting anion have little effect on adsorption of Cr(Ⅵ),but the influence of ionic strength on adsorption is very obvious.Removal of Cr(Ⅵ) decreased with ionic strength.Peanut shell can be reused many times.It isn't obvious modified peanut shell improves removal of Cr(Ⅵ).(2) The kinetic studies showed that Cr(Ⅵ) adsorption onto peanut shell accords with the second order model.The initial stage of the adsorption was controlled by interfacial diffusion.The adsorption can be followed by intraparticle diffusion model after 180min.(3) Thermodynamical isotherm for the adsorption of on the peanut shell were developed and equilibrium data were found to be fitted well to the Langmuir and the Freundlich isotherm models.From the parameters of Langmuir and Freundlich models,we can learn that the maximum uptake is 6.25mg/g and constant n is larger than 1,which shows it is favorable character.This study can provide some academic references for the treatment of wastewater containing hexavalent chromium.