Powdered and beaded sawdust materials modified iron (III) oxide-hydroxide for adsorption of lead (II) ion and reactive blue 4 dye.

The problems of lead and reactive blue 4 (RB4) dye contamination in wastewater are concerns because of their toxicities to aquatic life and water quality, so lead and RB4 dye removals are recommended to remove from wastewater before discharging. Sawdust powder (SP), sawdust powder doped iron (III) oxide-hydroxide (SPF), sawdust beads (SPB), and sawdust powder doped iron (III) oxide-hydroxide beads (SPFB) were synthesized and characterized with various techniques, and their lead or RB4 dye removal efficiencies were investigated by batch experiments, adsorption isotherms, kinetics, and desorption experiments. SPFB demonstrated higher specific surface area (11.020 m2 g-1) and smaller pore size (3.937 nm) than other materials. SP and SPF were irregular shapes with heterogeneous structures whereas SPB and SPFB had spherical shapes with coarse surfaces. Calcium (Ca) and oxygen (O) were found in all materials whereas iron (Fe) was only found in SPF and SPFB. O-H, C-H, C=C, and C-O were detected in all materials. Their lead removal efficiencies of all materials were higher than 82%, and RB4 dye removal efficiencies of SPB and SPFB were higher than 87%. Therefore, adding iron (III) oxide-hydroxide and changing material form helped to improve material efficiencies for lead or RB4 dye adsorption. SP and SPB corresponded to Langmuir model related to a physical adsorption process whereas SPF and SPFB corresponded to the Freundlich model correlated to a chemisorption process. All materials corresponded to a pseudo-second-order kinetic model relating to the chemical adsorption process. All materials could be reused more than 5 cycles with high lead removal of 63%, and SPB and SPFB also could be reused more than 5 cycles for high RB4 dye removal of 72%. Therefore, SPFB was a potential material to apply for lead or RB4 dye removal in industrial applications.