Removal of an anionic azo dye direct black 19 from water using white mustard seed (Semen sinapis) protein as a natural coagulant

In this study, standard jar tests were conducted using white mustard seed protein (WMSP) as a natural coagulant to remove direct black 19 (DB-19) from its aqueous solution. Comparative coagulation tests were performed using commercial polyaluminum chloride (PAC). The results showed that DB-19 removal by WMSP increased with increasing settling time and reached the maximum removal at 180 min. The DB-19 removal descended from 98.4 to 46.2% as pH increased from 4 to 10. The most effective temperature for DB-19 removal was 25 degrees C. The removal of DB-19 was weakened by the presence of Na2S2O4. Overall, WMSP was more efficient than PAC for DB-19 removal in all experiments except at pH 4 and 5. The mechanism of the removal of DB-19 by WMSP could be attributed to adsorption and charge neutralization processes.