This thesis investigates the optimization of washing techniques before bleaching a pulp produced using ionic liquids. One pulp is from softwood and the other from wheat straw. Through experiments with varied temperatures and concentrations, the effectiveness of different washing conditions was evaluated, focusing on their impact on kappa number, viscosity, yield and reject amount for the softwood pulp. The wheat straw pulp was studied using the same optimal washing conditions that gave the best results for the softwood pulp. The results showed that washing at 75°C with 1.5% NaOH was the most effective. After washing, the softwood pulp had a kappa number of 20.0 and a viscosity of 162 mL/g. For the wheat straw pulp, the best result was a wash with 1.5% NaOH at 75°C, resulting in a kappa number of 16.2 and a viscosity of 446 mL/g. The washing process proved effective on a laboratory scale and the next step will be to conduct pilot-scale trials. The trials so far show that there is potential to scale up the washing of pulp produced by ionic liquid-based cooking. After washing, bleaching was performed using sodium chlorite. This method was suitable for laboratory-scale experiments, leading to a kappa number reduction from 20.0 down to 0.39 for the softwood pulp, with a viscosity loss from 162 mg/L down to 152 mL/g and a brightness of ISO 85%. For the wheat straw pulp, the kappa number decreased from 16.2 down to 0.62, the viscosity fall to 272 mL/g from 446 mg/L and the brightness reached ISO 76%. The study demonstrates that washing parameters can be optimized to achieve high brightness of the final bleached pulp without significantly altering its physical properties. The kappa number decreases while the viscosity remains relatively stable for the soft wood pulp, indicating that the process can consistently produce the same results. The wheat straw pulp lost viscosity from a high level. Loss of viscosity must be expected in some extent. The insights from this study reveal that pulp produced with ionic liquids can be washed and bleached effectively under control. The control of loss of viscosity is crucial for industrial applications. Future process development will require efficient chemical recovery. It is not possible to have wastes out of the process. It will be essential to close the process and it will ensure the sustainability of the process.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kau-100766 |
| Date | January 2024 |
| Creators | Hashemi, Soraia |
| Publisher | Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf, application/pdf |
| Rights | info:eu-repo/semantics/openAccess, info:eu-repo/semantics/openAccess |
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