Synthesis of powdered and granular N -(3-trimethoxysilylpropyl)diethylenetriamine-grafted mesoporous silica SBA-15 for Cr(VI) removal from industrial wastewater

Abstract In this study, both powdered and granular N-(3-trimethoxysilylpropyl)diethylenetriamine (DAEAPTS)-grafted mesoporous silica SBA-15 were synthesized for hexavalent chromium (Cr(VI)) removal from industrial wastewater. The powdered adsorbents were synthesized via grafting DAEAPTS onto SBA-15. The Cr(VI) sorption characteristics of the adsorbents were examined under batch conditions in synthetic Cr(VI) solutions. Batch experiments revealed that the Cr(VI) sorption was favorable at acidic pH conditions with the greatest sorption at pH 3. The Cr(VI) sorption was a fast process, reaching equilibrium within 10 min. The maximum Cr(VI) sorption capacity was 330.88 mg/g. To overcome limitations of the powdered adsorbents for large-scale application (hydraulic and separation problems), the spherical granular adsorbents (average size = 1.13 ± 0.09 mm) were prepared through immobilizing the powdered DAEAPTS-grafted SBA-15 into a polymer blend (poly(vinyl alcohol) and sodium alginate). The granular adsorbents were applied for Cr(VI) removal from two industrial plating wastewaters in flow-through column experiments. In the experiment with wastewater 1 (Cr(VI) concentration = 328.7 mg/L), the Cr(VI) sorption capacity of the granular adsorbents was 158.8 mg/g. In the experiment with wastewater 2 (Cr(VI) concentration = 2671.6 mg/L), the pristine and regenerated adsorbents were tested to demonstrate that the granular adsorbents could be successfully regenerated and reused for Cr(VI) removal.