Abstract
Magnetic sodium alginate(SA)-based biogel composite Fe-SA-Y@Fe3O4 macroparticles were synthesized by co-crosslinking of Y(III) and Fe(III) ions according to the optimized preparation conditions and characterized by various modern analytical techniques. The results show that the macrogel beads have unique cauliflower-shaped surface and sensitive magnetic response. Fe-SA-Y@Fe3O4 composite was used for the removal of Direct Red 13 (DR 13) and Direct Black 19 (DB 19) dyes from water. The adsorption capacities and removal efficiency can reach 2487 mg/g and 99.5% for DR-13 and 2992 mg/g and 99.7% for DB-19 respectively within the equilibrium time of 60 min at 298 K and pH 2.0, and decrease slightly with pH up to 10.0. The kinetic and equilibrium adsorption data followed the Pseudo-second-order rate model and Langmuir isothermal model well, respectively. Electrostatic adsorption, various H-bonding and complexation were largely involved in dye adsorption processes with spontaneous and exothermic character by macrogel beads, which were explained by thermodynamic studies, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), respectively. Fe-SA-Y@Fe3O4 composite with ultrahigh adsorption capacity and fast magnetic separation property will be a promising eco-friendly bio-based adsorbent for the superefficient purification of practical azo-dye effluents.
Highlights
One of the main causes of environmental water pollution and harm to human health is the discharge of a large number of organic dyestuff wastewater produced in various industrial processes without treatment or incomplete pretreatment [1]
When the concentrations of SA solution and mixed solution of Fe(III) and Y(III) ions were fixed at 16 and 10 g/L respectively, mixed solutions with different ion mass ratios were used for the synthesis of Fe-SA-Y polymer at room temperature, and the obtained polymer was further applied to the adsorption of Direct Red 13 (DR 13) and Direct Black 19 (DB 19) dyes respectively
The dye adsorption amounts and removal rates reached the maximum values with 1247 mg/g and 95.9% for DR 13 and 1371 mg/g and 97.9% for DB 19 respectively when the dual-ion mass ratio was 2:1, indicating that the Fe-SA-Y polymer prepared by dual-ion cocrosslinking SA has extremely significant improvement on the adsorption efficiency of azo dyes from the water
Summary
One of the main causes of environmental water pollution and harm to human health is the discharge of a large number of organic dyestuff wastewater produced in various industrial processes without treatment or incomplete pretreatment [1]. Direct Red 13 (DR 13) and Direct Black 19 (DB 19), belonging to disazo and polyazo dyes, are often directly used for dyeing in producing industries of cellulose fibers, cotton, silk, leather, viscose and paper owing to their cheapness, good water solubility, color diversity, simplicity and directness of dyeing by H-bonding interaction and Van der Waals force [6]. These dyes are difficult to discolor, weakly biodegradable and potentially toxic due to their complex aromatic ring structures. Developing low-cost, eco-friendly, high-capacity and swift-separation adsorbents have become the key to the efficient implementation of adsorption technology [12,16]
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