Abstract
A coagulation/flocculation process using a selection of biopolymers (chitosan and tannin) was used to treat an ink-containing effluent generated in the processing of packaging. The efficiency of the process was investigated in terms of the influence of pH, coagulant and flocculant concentrations, as well as chitosan characteristics (especially the molecular weight). The process was particularly efficient under acidic solutions: the amount of coagulant and flocculant to be used were significantly reduced by limiting the pH to 5. Optimum conditions for colour abatement (measured at 528 nm) were obtained at pH 5 using the most viscous chitosan (highest molecular weight) at a concentration close to 20 mg·ℓ-1 and a concentration of tannin close to 70-100 mg·ℓ-1.. Water SA Vol.31 (3) 2005: pp.369-376
Highlights
The packaging industry frequently uses dyes, pigments and inks for the conditioning of cardboard boxes and the printing of advertisements
While an increase of tannin concentration improved the efficiency of the process for chitosan B1, the optimum efficiency was obtained at an intermediary concentration of tannins for chitosan B6 (i.e. 1 320 mg·l-1)
In high molecular weight chitosan at neutral pH amine groups may be involved in hydrogen bonds that cause polymer coiling and reduce the availability of amino groups
Summary
The packaging industry frequently uses dyes, pigments and inks for the conditioning of cardboard boxes and the printing of advertisements. Polyacrylamide is the basis of many flocculants and its discharge in the environment is considered hazardous due to the possible release of monomers that could enter in the food chain, with potential impact on health (carcinogenic effect) For these reasons, the research recently focused on the use of bio-coagulants and bio-flocculants (Chen et al, 2003; Strand et al, 2003; Tripathy et al, 2001). Tannins (polyphenolic products of plant origin) have recently received attention for their potential application in coagulation and flocculation due to their anionic behaviour in solution (Özacar and Sengil, 2000; 2003) These polymers are divided into two groups, namely, the condensed tannins which are derivatives of flavanols, and the hydrolysable tannins, which are esters of a sugar, usually glucose (Özacar and Sengil, 2003).
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