Use of dispersed and beads chitosan in liquid effluents treatment

Abstract

Chitosan, an amino-biopolymer, has received a great deal of attention in the last decades in the treatment of various suspensions and solutions for the removal of particulate and dissolved contaminants. The advantage of chitosan over other polysaccharides is that its polymeric structure allows specific modifications without too many difficulties. It is commonly prepared by deacetylating chitin in alkali solution. Contrarily to bibliography, two low temperatures (25 ± 2 and 30 ± 2 °C) and several days (10-15) have been chosen for deacetylation of purified chitins (chemical and biological). The aim was to produce soluble chitosan in diluted acetic acid solution (1%) and applying the chitosan in dispersed and gel beads forms for liquid effluents treatment as adsorbent for the removal of dye (Direct blue 71) from synthetic effluent (first application) and as bioflocculant for the capture of particulate suspension from drinking water plant effluent (second application) and for the improved settling of biological colloids such as bacteria from activated sludge after biological treatment of wastewaters (third application). This study demonstrated that chitosan prepared in soft deacetylation condition has conserved its high affinity for many classes of contaminants such as humic substances, inorganic matters, suspended solids, dye molecules and bacterial suspensions. Good results were obtained for the maximal reduction of turbidity and suspension matter at very lower concentration of dispersed biopolymer (1 mg/L and 1.5 mg/L in two effluents, respectively) and for the total removal of color in natural medium pH by adsorption at a ratio: 1g of beads/50ml of dye solution. Chitosans prepared in this study are all efficient if used dispersed and gels.