Superadsorbent aerogel based on sunflower stem pith cellulose and layered double hydroxides modified montmorillonite for methylene blue removal from water solution

Abstract

Sunflower stem pith, an agricultural residue, was used as a starting material for the preparation of bio-based products. Sunflower stem pith nanocellulose (SSP-C) was prepared by sodium hydroxide/urea from the SSP cellulose. The prepared SSP-C was typical of cellulose II. To improve the adsorption capacity of the SSP-C, a bio-based aerogel (SSP-MH) with adsorbed methylene blue (MB) was prepared by compounding layered double hydroxides modified montmorillonite (MH) with SSP-C-based adsorbent, and the chemical characteristics and topology of the adsorbent were determined. The removal performance of SSP-MH in different MB concentrations was examined. Adsorption tests showed that hydrogels containing the same content of MH had higher removal efficiency. The removal rate of MB by SSP-MH was >87.5 % in MB solution (1 g/L), and its maximum adsorption capacity was 263.3 mg/g. The kinetics studies of MB removal were well by quasi-secondary adsorption kinetic model and Langmuir isotherm model. Moreover, the standard free Gibbs energy change of adsorption (ΔG0) was <0, which was favorable for adsorption of MB. The adsorption efficiency of SSP-MH on MB was still above 95 % by the five cycles of the adsorption/desorption experiment. The prepared samples were conducive to the high-value utilization of SSP.