Optimization of vibratory nanofiltration for sustainable coffee extract concentration via response surface methodology

ABSTRACT

A vibratory nanofiltration (NF) system was investigated in the preconcentration of coffee extracts for soluble coffee production. Four different NF membranes were studied, among which the selected membrane (Trisep Microdyn TS80) rendered the highest permeate flux and rejection efficiencies. The vibratory NF operation also considerably improved permeate flux, rejection efficiencies, and reduced flux decline from those observed in crossflow (CF) operation. Further, the effects of applied transmembrane pressure (TMP) and module vibrational frequency (F) at corresponding displacement (d) were investigated via response surface methodology in conjunction with a Box-Behnken experimental design, as to their interactions on the performance of the vibratory NF operation. Mathematical models were statistically determined from multivariate regression analysis on permeate flux, maximum surface shear rate, permeate quality, and rejection efficiencies. These correlations were also used to determine optimum conditions (TMP = 3.79 MPa, F = 54.7 Hz, d = 3.18 cm) to process 25.4 g L⁻¹ coffee extracts. The observed responses from experimental verification were found to be in good agreement with the predicted values obtained by the reduced regression models.

KEYWORDS:

• Dynamic filtration
• nanofiltration
• vibratory membrane module
• soluble coffee
• design of experiments

Acknowledgements

The authors acknowledge the support of the U.S. Environmental Protection Agency through the Pollution Prevention Grant Program (NP-96271316-2). The authors also acknowledge the staff of the Department of Chemical Engineering, Rowan University: Rob McClernan and Kimberly Johnston; and Engineering Clinic students: Jacquelyn Shaeffer, Carly Jankowski, Adam Niznik, Matt Razze, and Ben Kayhart. The authors also appreciate the support of Landon Graham of New Logic Research, Inc.

Declaration of interest statement

We declare that this manuscript is original, has not been published before, and is not currently being considered for publication elsewhere. We know of no conflicts of interest associated with this publication and no significant financial support for this work that could have influenced its outcome. All named authors have read and approved the submission of the manuscript.

Additional information

Funding

This study was funded through the U.S. Environmental Protection Agency, grant NP-96271316-2.

Notes on contributors

Michael Vincent O. Laurio

Michael Vincent Laurio is a faculty member at the Department of Chemical Engineering, University of the Philippines Los Baños, Philippines, on study leave at the time of this research.