Modified Biosorbents For Adsorption Of Basic Magenta And Regeneration

In this study, the surface of beer yeast and bagasse were modified with achemical modification reagent, pyromellitic dianhydride （PMDA）, whichenhance their adsorption capacities for dye: basic magenta （BM）. In order tosolve the problems that the small particles of beer yeast were hard to recycle,the small ball embedded with calcium alginate was prepared. To decreasethe secondary pollution caused by the dye in the eluent, the in-situ methodwas used to prepare the magnetic P25photocatalyst which provided withgood photocatalytic activity and could be separated and recover fromsolution easily. The main results are as follow:1．For basic magenta the adsorption capacities of beer yeast and bagassewere improved after modifying with PMDA. FTIR demonstrated that a largenumber of carboxyl groups （–COO-） were introduced on the surface ofbiosorbents. The adsorption capacities of the modified beer yeast andbagasse for basic magenta were588.1and833.3mg·g^-1, respectively, whichwere1.8and6.7times than the unmodified ones. The kinetics of adsorptionwas fast, reaching equilibrium within630min for the modified beer yeastand645min for the modified bagasse. Ion strength experiments showed thatit had comparatively little effects on the adsorption capabilities of themodified adsorbents when the concentration of co-ion （K+） was lower than0.1mol·L^-1. The desorption experiments indicated that the modified beeryeast was regenerated with a desorption ratio of94.8%using0.1mol·L^-1HCl， while the modified bagasse was89.9%using HCl: EtOH （1:4）solution. After elution the adsorbents could be used repeatedly.2．The Langmuir isotherm model could well fit the adsorption processof the modified beer yeast and bagasse to basic magenta that demonstratethe adsorption took place in the monolayer form. The whole adsorptionprocess of basic magenta with the modified beer yeast and bagasse fitted the pseudo-second-order model better than the pseudo-first-order andintra-particle model. It indicated that the adsorption rate of the modifiedadsorbents was controlled mainly by the concentration of basic magenta andthe active sites on the surface of the adsorbents.3．The small ball embedded with calcium alginate was prepared. Theadsorption capacities of the small ball embedded the modified beer yeastwith calcium alginate were384.6mg·g^-1which were1.8times than the onesembedded the unmodified beer yeast. The Langmuir and Temkin modelisotherm models could well fit the adsorption process of the small ball tobasic magenta. Meanwhile, the whole adsorption process of basic magentawith the small ball embedded the modified beer yeast with calcium alginatefitted the intra-particle model that illustrated the adsorption of the embeddedball was controlled by the internal diffusion. The pH experiments showedthat the excessive acidic or alkaline were not good for the adsorption of thesmall ball embedded the modified beer yeast with calcium alginate to basicmagenta, and pH of the solution was near5which benefited for itsadsorption.To decrease the secondary pollution caused by the dye in the eluent, thewas used to which4．The magnetic P25photocatalyst prepared with the in-situ methodhad good photocatalytic activity and could be separated and recover fromsolution easily. The photodegradation experiments of the eluent containingBM showed that the magnetic P25was provided with good photocatalyticactivity and the degradation process fitted the pseudo-first-order model. Theapplication of magnetic photocatalyst in dealing with the eluent could avoidthe secondary pollution caused by the emission of the eluent.