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Mature fine tailings need to be dewatered to reduce the environmental impact caused by oil sands extraction. Polymer flocculants are commonly used to accelerate this process. In this work, we modified chitosan, a naturally occurring biopolymer, with 3-chloro-2-hydroxypropyl­trimethyl­ammonium chloride (Chito-CTA) and also grafted polyacrylamide to chitosan (Chito-g-PAM). We compared the dewatering performance of these two flocculants with that of a commercial cationic polyacrylamide (C-PAM). Chito-CTA and Chito-g-PAM dewatered tailings at rates of 18.27 and 20.72 m/h, respectively. The dewatering ability of Chito-CTA and Chito-g-PAM, measured in terms of capillary suction time (CST), was below 10 s, whereas the value for C-PAM was 82.3 s at optimum dosage. The turbidity of the supernatant obtained after flocculation with Chito-CTA or Chito-g-PAM was below 10 NTU, while C-PAM produced turbid supernatants. We studied the effect of flocculant microstructure on the specific resistance to filtration of the sediments. Chito-g-PAM produced sediments with the lowest resistance, 2.99 × 1012 m/kg, while C-PAM’s sediments had a much higher resistance of 40.26 × 1012 m/kg. We also used the focused beam reflectance measurement technique to determine floc size evolution, floc stability, and time required to induce floc formation. Our results indicate that chitosan-based polymers may be successfully used to treat oil sands mature fine tailings.

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Empty fruit bunch (EFB), an underutilized waste product of oil palm processing, was studied as a substrate for the production of humic acids (HA) by a Trichoderma reesei strain by solid-state fermentation (SSF) in Raimbault columns. HA have attracted the attention of many investigators due to their applications in agriculture, industry, the environment, and biomedicine. Commercial HA are currently chemically extracted from peat and coal, which are nonrenewable carbon sources. Biotechnological processes are important for their sustainable and controlled production, with SSF being especially promising for mimicking the natural habitat of fungi. Trichoderma sporulation and HA production are related, and the results of this study showed that SSF stimulated fast sporulation. The productivity related to HA was much higher than that of the biomass, indicating an efficient utilization of EFB. These findings, added to the low cost of EFB, make SSF an attractive process for HA production.

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The novelty of this study was to produce humic acids by submerged fermentation of empty fruit bunch (EFB) with Trichoderma viride and to investigate the effects of the cellulosic substrates and the organic sources of nitrogen on the biotechnological production of these acids. The results obtained indicate the potential application of EFB, a waste of oil palm processing, for humic acids production. Because EFB contains cellulose, hemicellulose and lignin, fermentations were also performed using these polymers as carbon sources, separately or in combination. After 120 h of fermentation, significant production of humic acids was observed only in cultures containing either EFB or a mixture of the three polymers. Use of either potato peptone or yeast extract as a nitrogen source yielded nearly identical patterns of fungal growth and production of humic acids. The data obtained from microscopic imaging of T. viride growth and sporulation in EFB, coupled with the determined rates of production of humic acids indicated that the production of these acids is related to T. viride sporulation.