Effect of enzyme type on the control of fluorescent whitening agents during recycling

The goal of this study was to develop an eco-friendly removal technology for fluorescent whitening agents (FWAs) using enzymes suitable for each type of FWA. Internally treated paper with internal FWA (D-FWA) and surface-sized paper with surface-sizing FWA (T-FWA) were made as model papers in a laboratory. The enzymatic treatments were applied to the stock prepared using these model papers by disintegration. Cellulase and (alpha-) amylase treatments were performed at 50 °C under the conditions of pH 3 to 4 and pH 7 to 8, respectively. After disintegration and enzymatic treatments, handsheets were made, and the fluorescence index and FWA reduction of these handsheets were determined for evaluating FWA removal during recycling. Because D-FWA gets strongly attached to cellulosic fibers, it could not be easily separated from the internally treated paper by disintegration. Up to 8.1% of D-FWA was removed by enzymatic treatment with high-activity cellulase. Amylase could not separate D-FWA from cellulosic fibers. In the case of T-FWA, ca. 41% was separated by disintegration, and an additional 24% was detached from surface-sized papers by high-activity amylase treatment. Therefore, cellulase was effective in removing internal FWA (D-FWA), and amylase was required for removing surface-sizing FWA (T-FWA) during recycling.