화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.49, No.5, 2380-2387, 2010
Electroflotation Combined with Flotation Deinking of Flexographic Newsprint
A semicontinuous flotation cell, which incorporated an electrolytic cell, was used to collect inks from newsprint pulp slurry. In general, longer pulping time has an adverse impact on deinking of 100% flexographic old newspaper or newsprint (flexo-ONP) while temperature has a positive impact on deinking. However, the use of electric field improved deinking efficiency-measured by the percent reduction in effective residual ink concentration (ERIC)-by as much as 5% at longer pulping time (25 min compared to 5 min). Higher temperature (40 degrees C compared to 25 degrees C) combined with the use of electric field further improved deinking efficiency by 5%. Furthermore, the impact of electric field assisted flotation is discussed in the context of the following variables: alkali charge (sodium hydroxide), float consistency (percent solids in the pulp suspension), surfactant and soap concentration, and the amount of flexo newsprint in a mixture of newspaper (or furnish)-newsprint. Unlike 100% flexo-ONP, the mixture of 48% flexo-ONP, 30% offset-ONP and 22% old magazine (OMG) contains both flexographic and offset inks, which have different ink sizes and chemistries. On average, considering all the variables, the use of electric field improved deinking efficiency by 3%. The best deinking efficiency was achieved at 1% consistency, when sodium hydroxide and surfactant and soap were added, combined with electric field. The deinking efficiency was corroborated with thermogravimetric analysis (TGA). Deinking efficiency is also discussed in terms of a deinking selectivity parameter called the Z-weighted factor.