Abstract
The conventional process to treat dye wastewater is the physicochemical treatment such as coagulation, flocculation and adsorption process. A new approach has been demonstrated to treat Congo red dye wastewater, which is the adsorption-coagulation hybrid process. Natural coagulant extracted from Hibiscus sabdariffa seeds is used as the coagulant while activated carbon is used as the adsorbent in this case study. The objective of this experiment is to study the significant factors that will affect the efficiency of dye removal. Then, the optimum conditions for the hybrid process is determined using Respond Surface Methodology (RSM). The variables are pH, initial dye concentration, coagulant dosage and adsorbent dosage while the response of experiment is the dye removal percentage. A three-level and four-variable Box-Behnken design (BBD) is used for the RSM. A total of 27 sets of experimental results is required to determine the optimum conditions. Jar test is used to conduct the experiment with the addition of coagulant and adsorbent simultaneously. Based on the regression model analysis and ANOVA, the highly significant factors that contribute to the dye removal efficiency through adsorption-coagulation hybrid process are pH of solution and initial dye concentration. The RSM results shows that the optimised process parameters for adsorption-coagulation hybrid process with Hibiscus sabdariffa seeds as the coagulant and activated carbon as the adsorbent are pH 2, initial dye concentration of 385 ppm, coagulant dosage of 209 mg/L and adsorbent dosage of 150 mg/L. The dye removal reaches up to 96.67% under optimum parameters.
Highlights
Synthetic dyes are commonly used in many industries, such as textile, paper, plastic, ink cartridge and paint manufacture factories
There are four variables tested in this experiment, which are pH of dye solution, initial dye concentration, coagulant dosage and adsorbent dosage
The analysis shows that the dye removal can reach up to 96.67% when the pH of CR solution is 2, initial dye concentration is 385 ppm, coagulant dosage is 209 mg/L and adsorbent dosage is 150 mg/L
Summary
Synthetic dyes are commonly used in many industries, such as textile, paper, plastic, ink cartridge and paint manufacture factories. The most conventional way of treating it is the physicochemical treatment This method involves the coagulation and flocculation process which use up various coagulants such as alum, lime and ferric [4]. The polyelectrolytes will neutralise the negatively charged dye molecules to form particle-polymer-particle complexes [4]. These contaminants will be precipitated in the form of chemical sludge when the treated water is further added with flocculants. The generated sludge contains a considerable amount of chemical residue such as iron and aluminium salts. These components are hazardous to human health and possess environmental impact. Natural coagulants possess a few crucial advantages compared to chemical coagulants, such as environmentally friendly (sustainable and biodegradable), toxic-free and safer for application
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