Study On Dyes Adsorption Properties Of Magnesium Hydroxide-modified Diatomite

In this paper, basing on the structure characteristics of diatomite, the adsorbentof modified diatomite were developed with the method of activated and combined thesecond composition, decoloration of the dyes was studied using magnesiumhydroxide modified diatomite. The main achievements are as follows:1. Magnesium hydroxide modified diatomite was prepared by solid phasegrinding method using MgCl₂, NaOH and activated diatomite as the starting materialsafter activation conditions were investigated. The samples were characterized by XRD,SEM, EDX and N2adsorption desorption method.2. The adsorption property of dyes which includes acid fuchsine, reactive redand methylene blue in aqueous solution by modified diatomite were studied withspectrophotometry. The effects of absorbent dose, adsorption time, pH, adsiorptiontemperature and NaCl concentration were investigated. The results showed that asacid fuchsine the decolorization rate could reach up to95%when absorbent dose is6g/L, adsorption time is1h, pH is6.0, temperature is25℃and NaCl concentration is1.2mol/L; as reactive red, the decolorization rate could reach up to97%whenabsorbent dose is4g/L, adsorption time is1h, pH value is6.0, temperature is35℃and NaCl concentration is4mol/L.3. Adsorption coverage over the surface of modified diatomite was studied usingLangmuir isotherm, Freundlich isotherm．The model parameters showed that as acidfuchsine Freundlich model was better in simulation of the adsorption isotherm andLangmuir model is better in simulation of the adsorption isotherm. The adsorptionprocedure is an exothermic and physical process.4.The kinetics model of dyes onto modified diatomite were investigated. Theadsorption process of dyes can be better described by the pseudo second order model.There are two factors influencing the adsorption rate may be the dye concentrationand adsorbent properties, or the square of dyes concentration.