Adsorption behavior of three-dimensional bio-adsorbent from maize stalk pith for methylene blue

Abstract

To realize the comprehensive and convenient utilization of the whole biopolymers and the natural biological structure of agro-residual stalks during the dye-wastewater treatment, we reported a simple and effective strategy to directly convert corn stalk pith (CSP) into a three-dimensional bio-adsorption material (DCSP) by degreasing treatment for purification of methylene blue (MB) wastewater by filtration. The unique anisotropic structure of DCSP provided well-developed channels and pores for mass transfer; Removal of lipids from parenchyma and vessel cells of CSP led to a larger specific surface area, promoting the exposure of adsorption sites. Due to these structural advantages, the DCSP column with 3 cm length could adsorb MB from water as high as 99.1% under the batch condition of 9 mL/min filtration rate, 5 mg/L MB solution with initial pH 6.5 at 35 ℃. As demonstrated by adsorption kinetics, isotherms and thermodynamics, this adsorption process was chemisorbed, multilayer, endothermic, spontaneous and random. According to breakthrough investigation, the prominent features like volume of MB solution at the breakthrough point, adsorbent exhaustion rate and column capacity were 3000 mL, 0.70 g/L and 7.33 mg/g, respectively, when the biofilter height was 45 cm. Its performances of adsorption capacity (7.0809 mg/g) and MB removal efficiency (0.1811 g/mg/min) during continuous process were superior to other biomass-based adsorbents previously reported. This approach provides an agricultural-waster stalks as efficient filters for dye remediation. • The defatted corn stalk pith (DCSP) acted as an excellent three-dimensional filter. • Porous structure with rich biopolymer promoted DCSP to adsorb methylene blue (MB). • The filter removed MB more than 99.0% in the batch adsorption system. • Filter had a low adsorbent exhaustion rate (0.70 g/L) via breakthrough analysis. • The adsorption rate constants of MB by DCSP was up to 0.1811 g/mg/min.