Optimization of coagulation-flocculation process for colour removal from Azo dye using natural polymers: response surface methodological approach

Abstract

The ability of organic polymer rich coagulants for colour removal from acid dye was studied. An improved method for the extraction of the active coagulant agent from the seeds was employed. The effects of four variables including pH, coagulant dosage, dye concentration and time were analyzed. Response surface methodology (RSM) using face-centered central composite design (FCCD) was used to optimize the four variables. Increase in the colour removal efficiency was higher in acidic solution pH. Accurate control of coagulant dosages gave optimum destabilization of charged particles and re-stabilization occurred at above 800mg/L dosages. Polymer performances were measured through time-dependent decrease in particle concentrations following aggregates growth. The verification experiment agreed with the predicted values having less than 4% standard error. Overlay contour plot was used to establish an optimum condition for the multiple responses studied. The response surface approach was appropriate for optimizing the coagulation-flocculation process while minimizing the number of experiments. Coagulants studied should be considered as an alternative for conventional coagulants that are widely used in dye wastewater treatment plants.

Multi-response optimization of the coagulation process of real textile wastewater using a natural coagulant

“…Dotto et al (Dotto et al, 2019) obtained similar results (pH ¼ 2) when studying the colour removal using NaCl-extracted MO, verifying the cationic protein nature of the MO, which can improve the coagulant activity at low pH values. Furthermore, at high pH values a competition between OHand the negatively charged contaminants may occur for polymer hydrolysis products (Obiora-Okafo & Onukwuli, 2017). Similar results were reported by Moghaddam et al (Sadri Moghaddam, Alavi Moghaddam, & Arami, 2010).…”

“…Peaks for maximum colour removal are clearly observed at low coagulant dosage. This confirms that the charge-neutralization and adsorption were the predominant mechanisms for the colour removal, since these mechanisms are usually dominant at low coagulant dosage (Obiora-Okafo & Onukwuli, 2017). Baptista et al verified that the highest removal rates in colour and turbidity were obtained when the lowest concentrations of MO coagulant were used.…”

“…Most of the coagulation studies using natural coagulants were conducted on synthetic textile waste (Kristianto et al, 2018;Suresh et al, 2019;Obiora-Okafo & Onukwuli, 2017;Onukwuli, Obiora-Okafo, & Omotioma, 2019;Dalvand et al, 2016) or surface water (Adesina, Abdulkareem, Yusuff, Lala, & Okewale, 2019), yet little attention was given to real waste samples. Until recently, the new trends in the field were directed towards investigating the performance of these natural coagulants on real waste samples for the purpose of finding better alternatives for industrial applications (Dotto et al, 2019;Rambe, 2018;Dos Santos, 2018).…”

“…Ahmad et al (Ahmad, 2018) utilized the Taguchi design of experiments and observed that temperature, pH and coagulant dosage were the most significant parameters affecting the coagulation process. Similarly, Obiora-Okafo and Onukwuli employed Response Surface Methodology (RSM) to optimize the coagulation process of different natural coagulants, including MO, for colour removal of Acid Red 101 in synthesized solution (Obiora-Okafo & Onukwuli, 2017). Optimum operating conditions were determined for each coagulant and the colour removal efficiency was observed to increase in acidic solution.…”

Acid Dye Removal from Aqueous Solution by Using Neodymium(III) Oxide Nanoadsorbents

“…Therefore, wastewaters containing this type of dyes were highlighted as one of the most important threatening factors in environmental and public health [2,5]. Different studies have reported that there are several methods for removing dyes from textile wastewaters, including the application of photodecomposition [6], electrolysis [7,8], adsorption [9][10][11][12][13][14][15][16][17][18], oxidation [19], biodegradation [20], combined sonochemical and adsorption [21], coagulation-flocculation [22,23], etc.…”