Browsing by Author "Rolence, Cecilia"

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An eco-friendly tanning method using plant barks and their combination with aluminium sulphate from kaolin for leather industry
(NM-AIST, 2021-02) Rolence, Cecilia
Chrome tanning has remained the most preferred tanning method worldwide in the leather industry because it produces leather of a high quality with all the desired features. However, environmental concerns of chromium shifted the focus of current research to chrome-free and greener chemical processing options. When used in combination with some eco-friendly metal salts, vegetable tannins are environmentally safe and manageable, while producing excellent quality leather, bearing shrinkage temperature above 100 °C as that of chromium tanned leather. As such, shortage of vegetable tannin supply requires characterization of non-commercialized sources locally available in Tanzania for cottage tanneries. In the present work, vegetable tannins from the stem barks of local plants namely Acacia mearnsii (A. mearnsii), Acacia xanthophloea (A. xanthophloea), Euclea divinorum (E. divinorum) and root barks of Euclea racemosa (E. racemosa) were prepared using a simple extraction technique at 30-80 °C. Extract yield, tannin, total flavonoid and phenolic content, cross-linking ability as well as properties of the tanned leather were determined. Results indicated that even at low temperature (50 °C) the barks yield vegetable tannins with features similar to that of a commercialized source of tannin. Euclea racemosa extract had low tannin, phenolic and flavonoid content and its crosslinking ability was poor; hence, was determined as an un-suitable tannin source. Despite recording less extract yield, tannin and other contents than that of A. mearnsii, the extract from E. divinorum bark demonstrated a substantial tanning ability, which is attributable to its high tannin strength. However, a broad interval between T onset and T peak of treated hide powder necessitated combination tanning with aluminium sulphate [Al 2 (SO 4 ) 3 ] to lower the interval. About 2% (w/v) aluminium oxide (Al 2 O 3 ) equivalent is an optimal dose of Al 2 (SO 4 ) 3 for extract pre-treatment. Since the main source of Al 2 (SO 4 ) 3 , bauxite, is diminishing in the world, an alternative source of Al 2 (SO 4 ) 3 was explored. The Al 2 (SO 4 ) 3 was prepared from Kaolin of Pugu hill in Tanzania and applied for combination tanning. The study has proven the suitability of kaolin as an alternative source of Al 2 (SO 4 ) 3 for combination tanning with vegetable tannins. Leather tanned with the combination of the prepared Al 2 (SO 4 ) 3 and vegetable tannin exhibited the shrinkage temperature of up to 118 °C as compared to vegetable tannins alone that showed the average of 80 °C. Mechanical strength characteristics met the standard norms. Fiber separation was good as confirmed through microscopic studies. The study provides useful information and new insights on accomplishing self-sustenance through available resources and an eco-friendly manufacturing system for leather industries in Tanzania and beyond.
Potentials of agric wastes activated carbons for water softening
(Research Journal in Engineering and Applied Sciences, 2014) Rolence, Cecilia; Machunda, Revocatus; Njau, Karoli
Various studies have been conducted to address softening of hard water. Ion exchange, electro-based techniques, membrane filtration and adsorption are the most reported techniques in softening hard water. In the present work, performances of these techniques are reviewed and discussed. Likewise, adsorbents that have so far been used in water softening, their efficiencies and drawbacks have been reported. Best adsorbent has been proposed based on optimum pH and local availability. In addition to the review of existing work on hardness removal, we have performed some preliminary experiments to study the performance of adsorbents, namely coconut and cashewnut shell activated carbons. The results are presented in here and it was found that, both adsorbents perform better in water softening but cashewnut shell activated carbon performs the best. These adsorbents are cheaply and locally available, which makes their integration into the softening systems low cost and highly performing owing to their chemical contents and subsequent activations.
Water hardness removal by coconut shell activated carbon
(Science Publishing Group, 2014-08-30) Rolence, Cecilia; Machunda, Revocatus; Njau, Karoli
The present study reports the water softening by adsorption of hardness ions onto Coconut Shell Activated Carbons (CSAC). Characterization of CSAC was identified by FT-IR and SEM techniques. Batch experiments were carried out to determine the effect of various adsorbent factors such as adsorbent dose, initial pH, contact time, and temperature, on the adsorption process using synthetic and field collected water samples. Removal efficiency at nearly neutral pH of 6.3 for both synthetic and field collected water samples were 60% and 55% respectively. Temperature study (303 K-333 K) shows that the softening process in synthetic and field hard water is endothermic as removal efficiency was increasing from 40% and 29% at 303 K to 47% and 38% at 333 K respectively. Removal efficiency increases with the increase in contact time and adsorbent dose until 15 hours and 0.24g/cm 3 respectively, for both field and synthetic hard water, which was considered to be maximum. Equilibrium isotherms have been analyzed using Langmuir and Freundlich isotherm models, and both Freundlich and Langmuir isotherm models fit to explain the adsorption behavior of hardness ions onto CSAC.