Coagulation and flocculation of dye wastewater by FeCl3 and mucilage extracted from dragon fruit peel (Hylocereus undatus) in regard of side effects caused by the use of PACl and PAM

Abstract

ABSTRACT Dye wastewater is the major and most polluted stream of wastewater generated from textile industry, which poses serious problems for the environment. Coagulation and flocculation have been the most practiced methods for dye wastewater treatment. However, the use of aluminum based coagulants and synthetic polymer are associated to human health; hence, iron based coagulants and plant-based polymers are alternatives of interest. This study determined the removal of turbidity and other pollutants from dye wastewater by a coagulation-flocculation process using FeCl 3 and mucilage extracted from the peel of dragon fruit Hylocereus undatus (DFPM) in regard to their alternative role as abovementioned. According to Jar-tests’ results, optimal coagulation conditions of FeCl 3 were typically found in pH 4.0–6.0 and settling time of 30–60 min, whereas, FeCl 3 dose varied in range of 0.15–0.26 mM depending on types of dye wastewater. The addition of DFPM (0.5–50 mg/L) after FeCl 3 (0.04–0.74 mM) resulted in turbidity removal up to 97%, corresponding to 10%–20% increase compared to those obtained with FeCl 3 alone. DFPM showed a comparable effect to the comercial flocculant – polyacrylamide (PAM) and the potential to decrease 10%–50% the amount of FeCl 3 used to obtain the similar turbidity removal. In comparison to polyaluminum chloride (PACl), FeCl 3 showed better coagulation performance on investigated dye wastewater; While achieving similar performance in turbidity, TSS, color and COD removal when combined with DFPM.

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