Optimum pH for lignin separation The Kraft black liquor of Eucalyptus camaldulensis Dehn. used in this study had an initial pH of approximately 12. The Kraft lignin was precipitated after adding sulfuric acid and the percentage yield of lignin following precipitation at various pH levels (2-6) are shown in Table 1. As would be expected, the yield of lignin depended on the precipitation pH, which was consistent with other reported results (Sun et al., 1999; Garcia et al., 2009). It has been found also that decreasing the pH results in an increase in recovered lignin, indicating that a lower pH tended to favor lignin recovery from the black liquor. For instance, there was an optimal precipitation pH of 2 for the recovery of lignin from the black liquor resulting from pulping the fiber in oil palm without fruit bunches, using 20% KOH and 0.1% anthraquinone (Sun et al., 1999). Moreover, it has been reported that lignin from soda pulping black liquor (7.5% NaOH) of Miscanthus sinensis precipitated at pH 2.57 exhibited similar characteristics to commercial alkaline lignin, even though the highest yield was found at pH 4.55 (Garcia et al., 2009).