Abstract
Spent pulping chemicals along with liberated lignin called black liquor are a major liquid waste stream from wood digestion process. For wastewater quality improvement, lignin residue could be isolated via various techniques. According to difference in chemical pulping process (kraft and soda), variations of organic and inorganic substance were suspended in waste stream. This research aims to investigate the effects of the cooking chemical on organic waste (lignin) in black liquor. Organic waste in black liquor was isolated as soda lignin (SL) from soda black liquor (SBL) and kraft lignin (KL) from kraft black liquor (KBL) by acidic precipitation. In addition, lignin model compound (LMC) was used to establish base case measurement. The elemental analysis revealed the similarity of C, H, and O content of samples in range of 32-33%, 3-4%, and 35-38%, respectively. FTIR results showed that structures of lignin, functional group and guaiacyl to syringyl ratio were vary depended on type of chemical pulping with β-O-4 as the primary composition of the samples. Moreover, Py-GC/MS technique was applied for analyzing the degradation products in order to corroborate the result with the structure and thermal behavior analysis. The TGA results showed high stability of lignin up to around 400°C. Main degraded compounds of all samples were phenol, vanillin, catechol, and guaiacol. This finding suggested that not only lignin which caused high BOD and COD could potentially be isolated for value added product but also the discharge quality could be improved. In addition, different chemical processes effect residual lignin in black liquor and underscore the importance of lignin in black liquor as a potential material for renewable energy and chemical production.
Highlights
The important necessity for human living and environmental balance is water controlled by natural influences e.g. geological, hydrological and climatic
This study focused on industrial black liquor and extracted lignin isolated from these samples
Black liquor from pulping industries has a potential for being the lignin source for production of fuel and chemicals normally derived from petroleum-based process
Summary
The important necessity for human living and environmental balance is water controlled by natural influences e.g. geological, hydrological and climatic. The anthropogenic activities have influenced the water quality [1], [2], especially the surface waters which are threatened with the pollution from domestic, agricultural, and industrial wastes. Is the essential water resource for any creature existing, discharges from their processes have been released into the natural water bodies. As the global competition and society pressure, emission reduction managements, especially the industry sector, are the requirement for sustainable development. [3] In Thailand, zero discharge is the measurement for industrial wastewater management to enforce the factory drainage quality. The treated wastewater met the standard requirement are lawful release, there are difficulty to limit the amount due to the specific process of each industrial type, e.g. pulp and paper industry.
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