High performance on the moisture reduction in waste oils by a bentonite-based adsorption process

ABSTRACT

In this work, the reduction of the moisture content from waste oils by a bentonite-based adsorption process was investigated as an alternative for reuse in energy production. Waste cooking oil (WCO) and waste poultry fat (WPF) were characterised (moisture and viscosity, values of acidity, saponification, and peroxide), as well as bentonite clay adsorbent. The response surface methodology (RSM) was applied to define the best moisture adsorption condition by bentonite-based adsorbent regarding a full factorial experimental design (FFED). In the framework of RSM, the adsorbent mass, oil acidity, and agitation speed were varied in three levels in the range of 1.5–3.0 g, 1–38 mg_KOH g_oil⁻¹, and 50–150 rpm, respectively, while the adsorption time was fixed in 24 h. Under the best moisture adsorption condition, kinetic tests were performed in a 1–24 h contact time range, besides performing equilibrium adsorption tests at 5 h contact time. Around 90% moisture removal was attained with 1.5 g adsorbent, acidity value of 1 mg_KOH g_oil^−1, and 50 rpm agitation speed, achieving the equilibrium in 5 h. A multilayer adsorption process, as described by the BET isotherm model, was acting in dried bentonite clay, allowing getting excellent moisture adsorption capacity (∼200 mg_water g_Bent⁻¹). Therefore, moisture removal from waste oils by a bentonite clay-based adsorption process has provided results that are suitable and recommendable for economically viable biodiesel production.

GRAPHICAL ABSTRACT

KEYWORDS:

• Waste oils
• moisture removal
• bentonite clay
• adsorption process
• experimental planning

Acknowledgments

F.R. Espinoza-Quiñones thanks the Fundação Araucária (protocol 009/15, project 43897) and Coordination for the Improvement of Higher Education Personnel (CAPES) and National Council for Scientific and Technological Development (CNPq, grant number 455954/2014-3) for financial support. Juliana Dotto thanks the Fundação Araucária for the award of the Ph.D scholarship.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Fernando Rodolfo Espinoza-Quiñones http://orcid.org/0000-0001-9012-0978

Helton José Alves http://orcid.org/0000-0001-6942-1020

Additional information

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico [grant number 455954/2014-3]; Fundação Araucária [grant number 43897].