Effect of steam explosion on adsorption properties of ginger fiber

Abstract: Ginger fiber(GF) is not suitable for textile due to its coarseness and it is usually disposed as wastes. This paper introduces a technology to make ginger fiber a valuable adsorbent of dyes in dyeing wastewater. The new technology is to explode the ginger fiber first by steam, and then frozen and disintegrate it to powder. We investigated the impact of a variety of factors in processing the ginger fiber on its ability to adsorb the dye RB19 in dyeing wastewater, which included the conditions under which the stream explosion was conducted, concentration of NaCl, and pH value. The surface morphologies and crystallization indexes of the ginger fiber before and after steam explosion were analyzed to elucidate the mechanisms underlying the improved adsorption of ginger fiber after steam explosion. Experimental results showed that steam explosion conducted under pressure1.9 MPa and lasting 150 s increased the adsorption from 48.8 to 115.12 mg/g. It was also found that several RB19 molecules aggregated to an ellipsoid with three axes: 33.4 ?×11.4 ?×8.8 ?. Breaking the ginger fiber surface enhanced the movement of RB19 molecules into the exploded ginger fiber powder(EGFP) and steam explosion made EGFP much richer in GF than in crystal index (CI). Increasing the pressure under which the steam explosion was conducted from 1.3 to 1.9 MPa reduced CI in EGFP from 35% to 20%, indicated that the steam explosion opened the amorphous region in the ginger fiber and that the expansion increased with pressure. As such, it enhanced the adsorption of RB19. The increased adsorption was mainly due to the broken surface. In addition, EGFP became small particles with a diameter of 80 μm, thereby enlarging the pores. Such structural changes made it easy for the dye molecules to move into the amorphous region of EGFP and improved its adsorption consequently. The steam explosion also increased the adsorbing rate, reducing the time required from the adsorption to reach equilibrium from 12 h to 8 h. The adsorption of RB 19 by the processed ginger fiber followed a second-order kinetic and the Langmuir thermodynamic model. After five cycles of adsorption-desorption, the adsorption capacity of the ginger fiber was still 80% of its original capacity. It is concluded that that steam explosion can effectively improve the adsorption capacity of ginger fiber. As a biomass adsorbent, EGFP can not only ameliorate the detrimental impact of dyeing wastewater on environmental but also turns a waste into a decontaminant amendment. It has potential applications in environmental engineering.