Mucilage Extracted from Dragon Fruit Peel (Hylocereus undatus) as Flocculant for Treatment of Dye Wastewater by Coagulation and Flocculation Process

Abstract

Dye wastewater from textile industries shows very low biodegradability due to high molecular weight and complex structures of dyes. So far, the most simple method for treatment of this type of wastewater has been coagulation and flocculation. This study determined the removal of turbidity and other pollutants from dye wastewater by mucilage extracted from the peel of dragon fruit (Hylocereus undatus) and its effect in reducing synthetic chemical polyaluminum chloride (PACl) used in coagulation and flocculation (CF) process. The removal of turbidity in a sequent CF process using PACl and dragon fruit mucilage was investigated based on Jar tests. Maximum coagulation efficiencies of PACl were typically observed at pH 4.0-6.0 and PACl concentrations of about 100-150 mg/L depending on types of wastewater, whereas optimal settling times were 30-60 minutes, respectively. The addition of dragon fruit mucilage (0.5-50 mg/L) after PACl (75-245 mg/L) resulted in turbidity removal efficiencies up to 95%. The addition of mucilage extracted from dragon fruit peels was proven to increase turbidity removal efficiency and decrease PACl use. The increase of turbidity removal was often estimated at 10-32%, whereas PACl used was about 3-10% less compared to total PACl needed for obtaining comparable efficiency when used alone. The flocculation activity of mucilage was also compared to polyacrylamide (PAM)—a synthetically organic flocculant. Since the peel of a dragon fruit is an abundant agriculture waste in Vietnam, using its extracted mucilage as a flocculant is an environmentally friendly method.

Removal of Pollutants From Disperse Black Dye Wastewater by Mucilage From Dragon Fruit Peel

“…This result matches with the researches of Lin & Peng [15] and Islam & Mostafa [16] in treating dye wastewater. Compared to research on three types of neutral dye wastewater of Le et al [13], the effective pH range of PAC was larger. This could be explained by more protons added in pH adjustment process, which supplemented more positive charges and increased the charge neutralization capacity of PAC.…”

“…The extraction process followed the steps presented in Le et al [13]. Dragon fruit peels were collected, washed and chopped to about 5 mm size and then dried at a temperature of 50 °C until constant weight.…”

“…Appropriate PAC dosage for treatment of textile wastewater in general and dye wastewater in particular is usually high. This ranged in 150-300 mg/L in Freitas et al, 100-400 mg/L in Islam & Mostafa, and 100 -150 mg/L in Le et al [13,16,23]. Optimal dosage is the most important factor for determining coagulation performance and computing the treatment cost.…”

“…galacturonic acid) and proteins in dragon fruit provide active sites at polymeric chain for particle adsorption and encourage coagulation process [8,11,12]. Mucilage extracted from Hylocereus undatus peel has been reported working effectively in the role of flocculant for treatment of different dye wastewater [13].…”

Biopolymer-based flocculants: a review of recent technologies

“…Besides, some researchers extracted mucilage from the peel of dragon fruit, and used it with polyaluminum chloride for turbidity removal. The results show that this kind of mucilage can reduce the dosage of polyaluminum chloride, and improve the removal rate of turbidity (Le et al 2020 ).…”