Microcrystalline cellulose (MCC) was functionalized with quaternary amine groups for use as an adsorbent to remove Congo Red dye (CR) from aqueous solution. The ultrasonic pretreatment of MCC was investigated during its functionalization. Characterization was conducted using infrared spectroscopy (FT-IR). X-ray photoelectron spectroscopy (XPS). https://chefesquipmenters.shop/product-category/accessories-toilet-and-urinal-parts/