Environmental Science and Technology p. 3647 - 3653 (1997)
Update date:2022-07-29
Topics:
Laszlo, Joseph A.
Cellulosics modified to contain quaternary ammonium groups have a strong affinity for anionic dyes. Therefore, ion exchangers based on quaternized cellulose or ligno-cellulose can be used to remove textile dyes from wastewater. However, restoration of exchanger binding capacity is poor using conventional, low-cost regenerants. Experiments were conducted with two monoazo dyes, Orange II (Acid Orange 7) and Remazol Red F3B (Reactive Red 180), to determine whether reductive cleavage of dye azo bonds improves exchanger regenerability. Treatment with the redox couple KBH4/NaHSO3 fully restored the binding capacity of Orange II-saturated quaternized cellulose. KBH4/NaHSO3 treatment of quaternized cellulose saturated with Remazol Red F3B (hydrolyzed, unreactive form) restored 74% of the exchanger binding capacity, which increased to 95% with a subsequent wash with NaOH or NaClO4. High-performance liquid chromatography was used to confirm that KBH4/NaHSO3 reductively cleaved dye azo bonds. Bisulfite was found to form a stable adduct with Orange II but to not cleave the dye's azo bond. The efficiency of dye azo bond reduction was the same for dye in solution and exchanger-bound dye. These results indicate that reduction of monoazo dyes is an efficient method by which to regenerate the dye binding capacity of quaternized cellulosics used to decolorize textile wastewater. Cellulosics modified to contain quaternary ammonium groups have a strong affinity for anionic dyes. Therefore, ion exchangers based on quaternized cellulose or ligno-cellulose can be used to remove textile dyes from wastewater. However, restoration of exchanger binding capacity is poor using conventional, low-cost regenerants. Experiments were conducted with two monoazo dyes, Orange II (Acid Orange 7) and Remazol Red F3B (Reactive Red 180), to determine whether reductive cleavage of dye azo bonds improves exchanger regenerability. Treatment with the redox couple KBH4NaHSO3 fully restored the binding capacity of Orange II-saturated quaternized cellulose. KBH4NaHSO3 treatment of quaternized cellulose saturated with Remazol Red F3B (hydrolyzed, unreactive form) restored 74% of the exchanger binding capacity, which increased to 95% with a subsequent wash with NaOH or NaClO4. High-performance liquid chromatography was used to confirm that KBH4/NaHSO3 reductively cleaved dye azo bonds. Bisulfite was found to form a stable adduct with Orange II but to not cleave the dye's azo bond. The efficiency of dye azo bond reduction was the same for dye in solution and exchanger-bound dye. These results indicate that reduction of monoazo dyes is an efficient method by which to regenerate the dye binding capacity of quaternized cellulosics used to decolorize textile wastewater.
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