Hatice Gecol

Use of surfactants to remove water based inks from plastic films

Abstract Direct reuse of plastic film with printing results in a colored polymer, which is less stiff and weaker than the original plastic upon re-extrusion. There is substantial economical and environmental incentive to remove the ink (deink) from heavily printed plastic film so that it can be reused to produce clear films. In this study, a commercial polyethylene film with water-based ink printing was deinked using different surfactants under a variety of conditions. At a pH of 12, water (containing no surfactant) can achieve about 90% deinking, but less basic solutions are less effective; at a pH 10 and below, insignificant-deinking occurs. Solutions of cationic surfactant are the most effective at deinking, showing high efficiency at surfactant concentrations both above and below the critical micelle concentration (CMC) over a pH range of 5–12. Amphoteric surfactant is effective above the CMC over a wide pH range. Both anionic and nonionic surfactants are only effective at deinking above the CMC at very basic conditions, with anionic surfactant being only slightly better than just water even at these high pH levels. The cationic surfactant is most effective and the anionic surfactant is least effective, possibly because the binder is an acidic acrylate with a negative charge.

Purification of Phenolic-Laden Wastewater from the Pulp and Paper Industry by Using Colloid-Enhanced Ultrafiltration

The removal of three phenolic pollutants with variable degrees of chlorination from water was investigated: 2-monochlorophenol (MCP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP). These compounds are often found in pulp and paper mill wastewater effluent. Colloid-enhanced ultrafiltration (CEUF) techniques were investigated for wastewater purification. Pollutants can associate with colloids: surfactant micelles or surfactant–polymer complexes solubilize nonionic compounds. In this application of CEUF, the micelles or surfactant–polymer complexes are ultrafiltered from solution with solubilized chlorinated phenol pollutant. An advantage of surfactant–polymer complexes, compared to only surfactants, is reduction of surfactant monomer (unaggregated surfactant) concentration. These surfactant monomers can pass through the ultrafiltration membrane, reducing the purity of the product water. Excellent solute rejections are observed for both micelles and surfactant–polymer complexes, generally exceeding 90% for DCP and TCP, even exceeding 99% in some cases. The ratio of the solubilization constant in micelles to that in surfactant–polymer complexes varied from approximately 1 to 5. In micelles, rejection increases in the order MCP<DCP<TCP, whereas in the surfactant–polymer system, rejection of the DCP and TCP can sometimes reverse order. The surfactant monomer leakage into the permeate for the surfactant–polymer system is only about 1 to 10% of that for the surfactant micelles, down to very low concentrations approaching 1 μM. Therefore, CEUF using surfactant-only or surfactant–polymer mixtures can be a very effective separation technique to remove chlorinated phenols from wastewater. Surfactant–polymer systems result in lower surfactant leakage, but somewhat poorer rejections of the pollutant. It is anticipated that it will be more difficult to recover the colloid for reuse compared to use of a pure surfactant.