ALTERNATIVES OF WASTE VALORISATION OF A SULPHITE PULP MILL IN CONSTRUCTION MATERIALS

Cellulose, which is found in the wall of cell plants, is the most abundant raw material and carbon source on Earth1,2. This, along with its low cost has increased the interest of valorising a whole variety of products, from... [ view full abstract ]

Cellulose, which is found in the wall of cell plants, is the most abundant raw material and carbon source on Earth^1,2. This, along with its low cost has increased the interest of valorising a whole variety of products, from bio-based polymers to energy. One of the main products is dissolving pulp, which can be obtained mainly in pulp and paper mills (about 85%) from woody biomass³.

Lignocellulosic materials have attracted a lot of attention to be used as a reinforcement material⁴. Not only because of the advantages shown before but also because of their recyclability, low cost, biodegradability and mechanical performance. In addition, they are non-toxic and non-abrasive⁴.

The two major processes to produce dissolving pulp are prehydrolysis kraft (PHK)  and acid sulphite (AS)⁵. The latter representing the 42% of the world production⁶.  AS dissolving pulp is obtained by the reaction of wood chips with a cooking liquor (H₂SO₃– HSO₃^-) under determined conditions to extract the cellulose from the  pulp. As a result, two main streams are obtained: (i) crude pulp, which needs  further purifications steps to obtain the final product, and (ii) spent sulphite liquor  (SSL) as by-product⁷, rich in lignosulphonates (LS) and sugars. In this work, a  review to obtain the main valorisation options of both streams in construction was  carried out. On the other hand, in order to assess the availability of SSL and  dissolving pulp to be used for the purpose mentioned above, a characterisation of  both streams was done in terms of: physico-chemical properties, composition,  morphology and thermal behaviour. As a result, it was determined that dissolving pulp could be used as a filler to produce light-weight ceramic materials, due to its thermal properties, and SSL (in the form of LS) to be used as plasticiser in  cements and mortar, in order to decrease their fragility. Future experiments will be carried out in order to study these alternatives.

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