Adsorption performance and mechanism of methyl orange by layered zinc hydroxide nitrate improved through flame spray pyrolysis method

Abstract

To adsorb methyl orange (MO) pollutant in wastewater, zinc hydroxide nitrate (ZHN) was synthesized by commonly-used chemical coprecipitation method (CCM) and the flame spray pyrolysis (FSP) method in this work. ZHN can efficiently adsorb MO pollutant. Specially, the adsorption capacity per unit mass of ZHN synthesized by FSP and CCM can reach 732.72 mg/g and 611.76 mg/g. ZHN synthesized by FSP possesses faster initial adsorption rate, larger adsorption capacity per unit mass and better adsorption characteristics for MO solution which may be due to the more voids between the lamellar of ZHN synthesized by FSP and the fact that the grain size, lamina thickness, and specific surface area of ZHN synthesized by FSP are 1/2, 1/6 and 4 times of those of ZHN synthesized by CCM, respectively. The adsorption kinetics of ZHN on MO is conformed to the pseudo-second-order kinetic equations. Moreover, at a low equilibrium concentration of MO, the adsorption behavior of ZHN is closer to the monolayer surface adsorption. When the adsorption on the ZHN surface tends gradually to the saturation with the increase of the equilibrium concentration, it will show the characteristics of interlayer adsorption.