Color removal of an aqueous solution containing water-based inks, a mixture of resins, pigments, and dyes, was investigated by using metal hydroxide sludge, which is a waste from the electroplating industry by Netpradit et al. [310]. The maximum adsorption capacity for the red ink was reported as 34.48 mg/g of metal hydroxide sludge. Waste metal hydroxide sludge was used as low-cost adsorbent for removing a reactive textile dye (Remazol Brilliant Blue) by Santos et al. [311]. The maximum adsorption capacity of 91.0 mg/g was found at 25 °C and pH 7.