A neutral deinking agent was applied for the deinking of laser printed papers under neutral or near-neutral conditions of pH. The results showed that a deinking efficiency of 93% could be achieved with a laboratory-made neutral deinking agent under optimum conditions. This neutral deinking agent, tagged as GWT, consists of anionic and nonionic surfactant, inorganic salt, etc. Optimum conditions were: GWT dosage of 2% (for dry recovered paper); pulping concentration of 10%similar to 20%; pulping temperature of 60 degrees C; pulping time of 25 min; conditioning time of 20 min; flotation concentration of 0.8%; and flotation time of 10 min. The neutral deinking technology is beneficial for the reuse of recovered paper due to its lower wastewater chemical oxygen demand (COD) and other chemical loads, thus resulting in lower treatment cost and environmental pollution compared with the regular alkali deinking process.
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