Production of a biodegradable flocculant from cotton and evaluation of its performance in coagulation-flocculation of kaolin clay suspension: Optimization through response surface methodology (RSM)

Abstract

Flocculants are widely used along with coagulant to increase the efficiency of coagulation-flocculation process for removal of colloidal particles from wastewaters. The most widely used flocculants are synthetic which have some problems such as non-biodegradability and release of toxic residual monomers. The main aim of this study is to evaluate the performance of cellulose sulfate (CS), which was synthesized through sulfonation of cotton, as a biodegradable and natural-based flocculant. Reaction time as an important factor in the sulfonation reaction was optimized for obtaining CS with high charge density and suitable fiber size. The sulfate content, charge density (CD) and morphology of each CS were determined to investigate and select the best CS for the flocculation process. A suspension containing kaolin clay was used as a colloidal test solution and coagulation was performed using alum (as a coagulant) and CS (as a flocculant). Optimization was performed using response surface methodology (RSM). The optimization results showed that CS had a good performance in turbidity reduction in coagulation-flocculation treatment and maximum turbidity reduction (98.9 %) was obtained at alum dosage of 23.1 mg/L, CS dosage of 7.2 mg/L and pH = 6.2. The results showed that the pH variation had insignificant effect on the CS dosage. Zeta potential measurements and microscopic photos of flocs confirm charge neutralization and bridge formation in flocculation using cellulose sulfate, respectively. Also, the total chemical consumption reduced compared with the use of alum alone. As a consequence, CS can be considered as a suitable alternative for conventional flocculants.

Optimization of coag-flocculation processes of a newly synthesized quaternized oil palm empty fruit bunch cellulose by response surface methodology toward drinking water treatment process application

“…The exact optimum settings to get the maximum e t ([99 %) were: coag-flocculant dosage, 60.19 mg/L; pH 6.5; and kaolin concentration, 1557.57 mg/L. Similar results were found by Nourani et al (2016) who used anionic cotton cellulose as a flocculant in removing positively charged kaolin suspension. The increased dosage and pH to a certain amount increased the removal turbidity to the maximum and then decreased at further increment.…”

“…Insufficient dosing resulted in inadequate cationic charge for the neutralization process causing an ineffective agglomeration of the particles (low e t ). However, an excess addition of coagulant and flocculant would initiate floc breakup due to charge reversal (Nourani et al 2016). The high turbidity removal at a high kaolin concentration was due to the increased amount of available suspended particles for adsorption and bridging formation.…”

“…Dicarboxyl cellulose from bamboo was synthesized via the Schiff base route which simplifies the complexity and heterogeneity of the traditional two-step method. Cellulose from cotton was also hydrolyzed and sulfonated with chlorosulfonic acid in dimethylformamide to obtain anionic flocculant for turbidity removal of kaolin suspension (Nourani et al 2016). Although many reports on natural compounds in water and wastewater treatment can be found, there are very limited reports on the application of the cellulose-based coag-flocculants for the drinking water treatment process.…”

Clarification of Pharmaceutical Wastewater with Moringa Oleifera: Optimization Through Response Surface Methodology

“…Since different variables are usually expressed in different units and/or have different limits of variation, the importance of their effect on the reponse can only be compared after they are coded (Nourani, 2016). Input variable pointed into a code as x = (x 1 ,..x k ).…”

“…RSM consists of statistical and mathematic techniques which provide comprehension in mathematic correlation between effective factors. Thus, the RSM methodology will be effectively used to optimize coagulation-flocculation process in wastewater treatment system (Harfouchi et al 2016;Nourani et al 2016).…”