Abstract
Spent alkaline solutions produced in the extraction cycle of cellulose fibers from Spanish broom (Spartium junceum L.) pose serious problems of environmental impact due to their high polluting load. A rationalization of the whole extraction cycle could be obtained through the recycling, purification and reuse of the extracting solutions with significant reduction of the polluting load.In this work the use of ceramic microfiltration (MF) and ultrafiltration (UF) membranes in tubular configuration was investigated for the treatment of spent alkaline solutions coming from the extraction of cellulose fibers in order to obtain a suitable solution reusable for new extraction cycles. For UF membranes with molecular weight cut-off of 1 and 3kDa, the effect of transmembrane pressure (TMP) and cross flow velocity (CFV) on the permeate flux, total organic carbon (TOC) and lignin content was investigated.An integrated membrane process was proposed on the basis of experimental results. It includes a preliminary treatment of MF devoted to the removal of suspended solids from the spent solution, followed by a UF treatment of the microfiltered solution with 1kDa tubular membranes. In optimized operating conditions (TMP, 4.5bar; CFV, 8.0m/s; temperature, 25°C) the UF membrane showed a rejection toward TOC and lignin of 68.9% and 86.8%, respectively, and a steady-state permeate flux of about 12kg/m2h. The integrated process permitted to reduce the initial TOC of the spent solution of 80%, producing a final permeate stream that can be reused for new extraction cycles.
Published Version
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