Article pubs.acs.org/IECR
Effective Lifetime Study of Commercial Reverse Osmosis Membranes for Optimal Hydrogen Peroxide Ultrapurification Processes Ricardo Abejón,* Aurora Garea, and Angel Irabien Departamento de Ingenierías Química y Biomolecular, Universidad de Cantabria, Avda. Los Castros s/n, 39005 Santander, Cantabria, Spain S Supporting Information *
ABSTRACT: The present work is focused on the effective lifetime of reverse osmosis membranes when they are applied to the ultrapurification of aqueous hydrogen peroxide solutions, considering the very exigent purity requirements in such an oxidant medium. The comparison of commercial polyamide and cellulose acetate membranes was performed from experimental data of permeate flows and solute rejections. The obtained experimental results were adjusted to the Kedem−Katchalsky membrane transport model. The analysis of the time behavior of the membranes and the effective lifetime determination are essential in the evaluation of the economic aspects of the industrial scale installation as these properties determine the replacement rate of the membrane modules, especially for resulting extremely short effective lifetimes (only a few days). A logistic decay model was proposed for the description of the rejection coefficients of solutes as functions of the operating time. Lastly, an optimization routine was carried out to obtain optimum values for operation variables to maximize the economics of the hydrogen peroxide ultrapurification process.
1. INTRODUCTION Electronic chemicals (chemicals and materials used to manufacture and package semiconductors and printed circuit boards) are required to contain an extreme low content of metallic impurities to avoid reliability problems attributed to loss of oxide integrity or shortening of minority carrier lifetime. Hydrogen peroxide is one of the most consumed wet electronic chemicals. Hydrogen peroxide is useful for removing photoresists and cleaning silicon surfaces. It is present in several mixtures employed in the silicon wafer cleaning sequence to eliminate organic matter, particulate contamination, and metallic impurities. As a consequence of the direct contact between hydrogen peroxide and silicon surfaces, high purity requirements are imposed on hydrogen peroxide for it to be accepted as an electronic chemical. SEMI, the Semiconductor Equipment and Materials International Association, is the entity serving the manufacturing supply chains for the microelectronic, display, and photovoltaic industries. SEMI assists the worldwide development of the most respected technical standards in this technological sector. Among all the topics regulated, some refer to the electronic chemicals characteristics. For the particular case of hydrogen peroxide, the SEMI C30-1110 document defines the requirements the chemical must fulfill to be considered as an electronic grade chemical.1 As seen in Table 1, which shows the limits imposed by the SEMI document to hydrogen peroxide as function of the five defined quality grades, the metallic content is limited from several ppb in the least strict electronic grade 1 to just 10 ppt in the most exigent electronic grade 5. Several metallic elements present as impurities in technical grade hydrogen peroxide exceed the limits fixed by the SEMI document. Consequently, ultrapurification processes are needed to achieve electronic grade requirements. Distillation, © XXXX American Chemical Society
adsorption, ion exchange, and membranes technologies are the most relevant techniques when electronic grade chemical is desired. The requirement of inert columns made of fluoropolymers (poor heat conductors) stresses the energy demand of distillation. Maximum efficiencies by adsorption processes are not comparable with results by ion exchange or membranes technologies. Regeneration of exhausted ion exchange resins implies waste streams and use of hazardous chemicals (strong acids and bases). Therefore, membrane technologies (mainly reverse osmosis) emerge as the most desirable ultrapurification option according to environmentally friendly criteria. Auxiliary chemicals are not needed, and zero effluent generation can be achieved since the retentate stream can be commercialized as nonelectronic grade for other industrial uses. However, the hydrogen peroxide ultrapurification process can be considered as a very demanding challenge for reverse osmosis membranes, because such an oxidant medium could promote the degradation of the polymeric membranes. In any case, the membrane sector has acquired important experience about oxidative degradation as a consequence of the common use of oxidant chemicals (typically chlorine) to avoid biofouling.2−9 Degradation of reverse osmosis membranes and membrane modules after contact with chemicals can take many forms, such as oxidation or hydrolysis of the membrane, and peeling off of the membrane structure in the module itself .10 Cleaving of hydrogen bonds between polymer chains and cleaving of the polymer chains themselves are the two main mechanisms by Received: September 3, 2013 Revised: November 6, 2013 Accepted: November 7, 2013
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dx.doi.org/10.1021/ie402895p | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Industrial & Engineering Chemistry Research
Article
Table 1. Impurity Limits and Other Requirements for Electronic Grade Hydrogen Peroxide According to the SEMI C30-1110 Standard SEMI electronic grade
assay (H2O2)
1 2 3 4 5
30−32% 30−32% 30−32% 30−32% 30−32%
total oxidizable carbon (TOC) limit 20 20 20 10 10
ppm ppm ppm ppm ppm
anion limit range
cation limit range
2−5 ppm 200−400 ppb 200−400 ppb 30 ppb 30 ppb
10−1000 ppb 5−10 ppb 1 ppb 100 ppt 10 ppt
Table 2. Characterization of Technical Grade H2O2 by ICP−MS element
concentration (ppb)
element
concentration (ppb)
element
concentration (ppb)
Li B Na Mg Al K Ca
