The Use of Coconut Shells for the Removal of Dyes from Aqueous Solutions

The main purpose of the work was to check the possibility of using coconut shells for the removal of the dyes popular in the textile industry from aqueous solutions. The sorption abilities of an unconventional sorbent were tested against four anionic dyes: Reactive Black 5, Reactive Yellow 84, Acid Yellow 23, Acid Red 18 as well as two cationic dyes: Basic Violet 10 and Basic Red 46. The scope of research included investigation pertaining to the effect of pH on the effectiveness of sorption of dyes, conducted in order to determine the time of equilibrium of sorption and determine the maximum sorption capacity of coconut shells with respect to pigments. The most favorable pH of sorption for the anionic dyes and Basic Violet 10 was pH 3 and for Basic Red 46 - pH 6. The equilibrium time of sorption was the shortest in the case of acidic dyes (Acid Yellow 23/Acid Red 18 - 45 min), while the longest in the case of alkaline dyes (Basic Red 46 - 90 min, Basic Violet 10 - 180 min). The sorption capacity of coconut shells in relation to anionic dyes was for Reactive Black 5 - 0.82 mg/g, Reactive Yellow 84 - 0.96 mg/g, Acid Yellow 23 - 0.53 mg/g and for Acid Red 18 - 0.66 mg/g. The tested sorbent showed much higher sorption capacity with respect to the cationic dyes, i. e. Basic Violet 10 (28.54 mg/g) and Basic Red 46 (68.52 mg/g).