Competitive removal of textile dyes from solution by pine bark-compost in batch and fixed bed column experiments

Abstract

Compost from pine bark has been previously suggested as an effective low-cost biosorbent for different classes of textile dyes, although the existing studies have been performed in non-competitive batch conditions, so the effect of competition or adsorption in continuous-flow conditions has not been assessed. In this work, the removal of Basic Violet 10 (BV10) and Direct Blue 151 (DB151) by pine bark compost from single and bi-solute mixtures has been studied in batch and fixed-bed column experiments. Adsorption capacity of pine bark compost was three times higher for BV10 than for DB151 in batch conditions, where competition reduced the uptake of both dyes, with competition factors of 0.63 for DB151 and 0.82 for BV10. Dye adsorption capacity was lower in column than in batch tests, with 112.6 and 34.7 mg g−1 for BV10 and DB151, respectively, versus 127.1 and 42.1 mg g−1 in batch conditions. The presence of both dyes in solution also reduced their affinities with respect to non-competitive conditions in column tests, with saturation capacities of 71.6 mg g−1 for BV10 and 16.8 mg g−1 for DB151. The effect of competition between dyes was higher in columns than in batch conditions, with competition factors of 0.76 for BV10 and 0.59 for DB151. The column biosorbent was effectively regenerated using ethanol, thus enabling reuse in the practical application of compost for textile dye removal. The concentration of dyes in the eluted ethanol was higher than the influent concentration, what would give compost value for pre-concentration of textile dyes