Abstract
This work deals with the use of carnauba wax as an expansion and hydrophobicity agent for vermiculite, to be utilized in the sorption process of oil in water. Evaluation of the system (oil-water-hydrophobic vermiculite) submersion percentage was considered in assessing the performance of vermiculite in comparison to a Mexican turf. Carnauba wax seems to be more efficient in both fresh and salt waters.
Hydrophobic agent; carnauba wax; vermiculite
CARNAUBA WAX USED AS AN HYDROPHOBIC AGENT FOR EXPANDED VERMICULITE
M.A.F. Melo, D.M.A. Melo and C.H.C. Pinto
Universidade Federal do Rio Grande do Norte - Centro de Tecnologia -
Departamento de Engenharia Química
Fone: 084-215.3826 CEP:59078-970 - Natal - RN - e-mail: dulce@quimica.ufrn.br
(Received: February 13, 1997; Accepted: September 8, 1997)
Abstract - This work deals with the use of carnauba wax as an expansion and hydrophobicity agent for vermiculite, to be utilized in the sorption process of oil in water. Evaluation of the system (oil-water-hydrophobic vermiculite) submersion percentage was considered in assessing the performance of vermiculite in comparison to a Mexican turf. Carnauba wax seems to be more efficient in both fresh and salt waters.
Keywords: Hydrophobic agent, carnauba wax, vermiculite.
INTRODUCTION
The Northeast region of Brazil is the major producer and exporter of carnauba wax, with 73% of the total regional production being exported., Since 1981 there has been a deterioration in this sector due to the low prices on the international market. As a result, carnauba plantations have been replaced by other types of forming. The physical and chemical characteristics of carnauba wax make it suitable for use as an auxiliary in various industrial processes mainly in the textile, food, paper and cosmetic industries. The chemical composition of the wax depends on the plant from which it is extracted, though esters represent the highest percentage at to 80-90%. Other chemical compounds include alcohol, glycol, hydrocarbons, ash and water, each of these at a percentage of about 10%. Some of its physical properties, such as the freezing point (82.8 - 85.2)oC, saponification index (70 - 84), acidity index (1.0 - 5.0) and iodine index (8.5 - 10.7) also depend on the plant species[2].
The mineral argil vermiculite is made up of hydrated aluminium silicate, showing negative charge deficiencies due to the naturally occurring substitutions in the tetrahedral layer. These charge deficiencies are normally neutralized by magnesium surrounded by water. These interlamelar waters can be extracted by a heating process thus causing an expansion in the mineral argil and a subsequent reduction in its apparent density. The resulting product could be used in the manufacture of light wood ply, for thermal and acoustic isolation, as an absorbent for residual water purification, for removal of polluting oil layers on the sea surface water etc[5]. Expanded vermiculite is used commercially in its granulometric form with a retention of 2.5 (8.0 mm) and 32 (0.5 mm) in the TYLER strainers. Vermiculites commercial value also depends on the type, quality of the commercialized form and the proposed final use. The existing supplies in Brazil could last for a long production period, which attests to the viability of projects in this field of work[1].
Expanded vermiculite made hydrophobic with carnauba wax could help fight pollution caused by accidental oil spillage in water, thus contributing to minimize the effects of this type of pollution, to improve the mechanical processes of oil recovery and finally to increase the value of the vermiculite processing industries, as well as industrialization of carnauba wax[3-4].
METHODOLOGY
Samples of raw vermiculite characterized by means of microgranulometry as micro (0.5 mm), superfine (1.0 mm), fine (2.0 mm), medium (4.0 mm) and large (8.0 mm), were provided by EUCATEX Mineral Ltda, situated in Paulistana, PI, and their characteristics are shown in Table 1.
The carnauba wax was provided by Machado S.A. Comércio e Indústria of Fortaleza, CE. The oil was obtained from Petrobrás, specifically from the Região de Produção do Nordeste Setentrional (RPNS), the Ubarana field in the State of Rio Grande do Norte. Its chromatographic profile shows high contents of normal paraffin (with a maximun of C8) and smaller quantities of branched nafthenic and aromatic isomers. Characterization of these products is shown in tables 3 and 4.
The expansion process consists of sample heating, and in this study raw vermiculite characterized as superfine (0.595 - 1.00 mm) was used. The sample was heated to 800oC for 2 minutes. The expansion was confirmed by apparent density measurement. The same sample was then used in the hydrophobic process with the agent already mentioned.
In the hydrophobic processing, 10g of the material were heated at 200oC, stirring constantly for a period of two minutes while the hydrophobic agent was slowly added. After the material became hydrophobic it was cooled to room temperature and placed into a glass container. Hydrophobic vermiculite was then sent for sorption testing of the oil in fresh water and in salt water and its performance was assessed by measurement of its sorption capacity and the sinking percentage of the oil / vermiculite hydrophobic system in water.
The method used consists of the preparation of a water / oil mixture with a 20 g/l concentration in a 600 ml beaker, using 300 ml of water (either fresh or salt), while the sorption factor is qualitatively measured with a quick stirring after 4 hours of contact. It can be classified as very good, good, and bad. The sorption factor (Sf/Fs) was considered very good whenever the hydrophobic vermiculite absorbed all the oil, including the supernatant monolayer; good when only the supernatant layer remained and bad whenever oil was found after the process, thus showing the inefficiency of the hydrophobic agent. In order to assess the sinking percentage of the oil/hydrophobic vermiculite; a 10% parameter was established during a 30 day period of contact. Figure 1 shows a generic flow chart of the hydrophobic process of vermiculite at the laboratory level[3-4].
RESULTS AND DISCUSSION
In this work a superfine granulometric vermiculite (0.5 - 1.0mm) as specified by Eucatex Mineral Ltda, (Table 1), was used. Chemical analyses and DRX show an unitary cell, (Mg,Ca, K, Fe++)3 ( Si, Al, Fe+++)4 O10 (OH)2 4H2O compatible with results.
The hydrophobic vermiculite sorption factors and those of the Mexican turf were regarded as very good since both materials adsorbed all the supernatant oil, including that of the supernatant monolayer, thus confirming the efficiency of the hydrophobic agent.
The values for the sinking percentage are shown in Table 3 and Figure 2. The results suggest that the sinking percentage for samples A and B does not exceed the 10% parameter during the 30 day contact, proving that both the hydrophobic vermiculite using carnauba wax and the turf could be used to fight pollution caused by oil spillage in water, but that the first (sample "A") proved to be ten times more efficient in fresh and salt water. This confirms the importance of the nature of the hydrophobic agent and that the ionic concentration has some influence on the sinking percentage.
CONCLUSION
The study showed that it is possible to develop alternative processes which can be competitive in efficacy and price to fight pollution caused by the spillage of oil in water, and that both the hydrophobic vermiculite using carnauba wax, as well as the imported product (Mexican turf), proved to be efficient, and that this efficacy depends on the hydrophobic agent, specific area to be covered, thermal treatment and eletrolytic concentration of the medium.
The application of hydrophobic vermiculite on waters polluted by oil can be done using low pressure jet equipment such as sand jets. It is of the utmost importance to keep a strategic stock at the location at risk, in order to facilitate quick action, since oil emulsifies a few minutes after spillage, of in moving bodies water.
(*) Note: varies with granulometry and density - SOURCE: Eucatex Mineral Ltda.
SOURCE: Petrobrás - S.A.
Descending percentage and apparent density for the hydrated oil / water / vermiculite system
A = Hydrated sample with carnauba wax, d = 0.30 g/cm3
B = Mexican turf
- Anuário Mineral Brasileiro, Departamento Nacional da Produçăo Mineral, Índice Acumulado 1983-1989 (1990).
- Brito, W.M.L., Contribuiçăo ao estudo da cera de carnaúba e suas aplicaçőes tecnológicas. Emulsőes, Masters thesis, Chemical Engineering, Federal University of Rio Grande do Norte (1992).
- Melo, M.A.F. et al, Processos de hidrofobizaçăo de vermiculita expandida, COBRASP, Maringá - PR (1995).
- Pinto, C.H.C., Vermiculita hidrofobizada como agente adsorvente de óleo em águas, Natal - RN, Masters thesis, Chemical Engineering, Federal University of Rio Grande do Norte (1994).
- Santos, P.S., Cięncia e Tecnologia de Argilas, 2d ed., Săo Paulo: Edgar Blucher Ltda (1992).
Publication Dates
-
Publication in this collection
09 Oct 1998 -
Date of issue
Mar 1998
History
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Accepted
08 Sept 1997 -
Received
13 Feb 1997
