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Applications of Polymer, Composite, and Coating Materials
Use of response surface methodology to develop and optimize the composition of a chitosan-polyethyleneimine-graphene oxide nanocomposite membrane coating to more effectively remove Cr(VI) and Cu(II) from water Pasan Chinthana Bandara, Enrico Tapire Nadres, and Debora F. Rodrigues ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b03601 • Publication Date (Web): 19 Apr 2019 Downloaded from http://pubs.acs.org on April 19, 2019
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ACS Applied Materials & Interfaces
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Use of response surface methodology to develop and
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optimize the composition of a chitosan-
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polyethyleneimine-graphene oxide nanocomposite
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membrane coating to more effectively remove
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Cr(VI) and Cu(II) from water
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Pasan C. Bandara†, Enrico T. Nadres†, Debora F. Rodrigues†*
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Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204-4003. Email:
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ABSTRACT
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Response surface methodology (RSM) was successfully used to optimize the amounts of chitosan
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(CS), polyethyleneimine (PEI), graphene oxide (GO), and glutaraldehyde (GLA) to produce a
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multifunctional nanocomposite membrane coating able to remove positively and negatively
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charged heavy metals, such as Cr(VI) and Cu(II). Batch experiments with different concentrations
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of the four coating components (GO, CS, PEI and GLA) on cellulose membranes were carried out
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with solutions containing 10 ppm Cr(VI) and Cu(II) ions. Reduced quadratic equations for the
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Cr(VI) and Cu(II) removals were obtained based on the observed results of the batch experiments.
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The numerical analysis resulted in an optimized solution of 30-min soaking in CS, 1.95% PEI,
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1000 ppm GO and 1.68% GLA with predicted removals of 90±10 % and 30±3% for Cr(VI) and
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Cu(II), respectively, with a desirability of 0.99. This mathematically optimized solution for the
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coating was experimentally validated. To determine the best membrane material for the coating,
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stability of the nanocomposite coating was determined using attenuated total reflectance - infrared
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(ATR-IR) spectroscopy in eight membrane materials before and after exposure to four solutions
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with different water chemistries. The glass microfiber (GMF) membranes were determined to be
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one of the best materials to receive the coating. Then, the coated GMF filter was further
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investigated for the removal of Cr(VI) and Cu(II) in single and binary component solutions.
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Results showed that the coatings were able to remove successfully both heavy metal ions,
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suggesting its ability to remove positively and negatively charged ions from water.
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Keywords: Chromium, Copper, graphene-oxide, nanocomposite, chitosan, water treatment,
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response surface methodology
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1. INTRODUCTION
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Recently, indirect potable reuse (IPR) has gained attention as an important sustainable
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water management process.1 For communities with limited water resources available, IPR seems
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to be a promising water management option in terms of water sustainability. IPR can achieve high-
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quality recycled water in compliance with the drinking water standards. Recycling efforts,
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however, need to be completed with the continuous evaluation of the potential health effects of
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treated recycled water for drinking purposes, since based on the origin of the wastewater, it could
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still contain very low hazardous contaminant concentrations after treatment. 1-3
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One group of contaminants that can be hazardous even at low concentrations is heavy
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metals. Among the heavy metal removal techniques, there are electrodialysis4, coagulation,
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flotation5, activated carbon adsorption6, ion exchange, reverse osmosis, and chemical reduction
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and precipitation.7 From these, efficiency of the chemical precipitation technique depends on
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different factors, such as pH adjustment, flocculation, and the concentrations of the ions involved.8-
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generate hazardous wastes. The other methods usually require long contact times. Thus, the
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production of potable water with the current methods can be expensive, and time-consuming.
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Therefore, it is important to search for alternative water treatment methods that are economical,
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efficient for the removal of different water contaminants. In search of such alternatives, many
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recent studies have shown potential use of nanotechnology and nanomaterials to remove numerous
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toxic contaminants efficiently and effectively from different contaminated water sources via
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adsorption.10 Among other advantages, nanomaterials do not generate brines or other disinfectant
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byproducts during the adsorption processes and has been considered as an economically viable
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technology for wastewater and water treatment.11
Even though chemical precipitation is used widely, this technique requires chemicals and
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Graphene and its derivatives have been more recently widely investigated for water
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treatment purposes as they provide the potential for the modification or functionalization of its
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carbon backbone for better removal of contaminants.12-13 Graphene oxide (GO) is a chemically
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modified version of graphene that has been highlighted as a promising counterpart for diverse
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applications.14-17 GO has shown excellent antimicrobial properties against bacteria.17-20 In
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addition, GO can adsorb a vast range of cationic and anionic contaminants such as heavy metals
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and industrial cationic dyes.10, 21 These removal capabilities are due to the physical properties of
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GO and the functional groups in GO such as -OH and -COOH, which can uptake positively and
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negatively charged particles via a process of chemical uptake and adsorption.20-21
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Furthermore, GO is cost-effective and can be used in large-scale production of graphene-
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based materials or composites.14,
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incorporating such nanomaterials with polymeric substances to provide functional variety,
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structural strength, and stability. Research in the synthesis of nanocomposites for water treatment
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is favored by the fact that the properties of GO or graphene-based nanomaterials in general can be
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enhanced by the polymers. Adsorption capacity, selectivity, lowering life-cycle cost, improved
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design flexibility, and potential for large-scale fabrication are some of the advantages of
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incorporating GO into polymeric matrices.23-24 In the present study, a combination of selected
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polymers with graphene oxide was used to develop and optimize a more efficient, effective, and
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multi-functional class of nanocomposite adsorbent for indirect potable water reuse treatment using
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the response surface methodology (RSM). RSM is considered as an effective method to understand
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the relationships between several independent variables and one or more response variables. The
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RSM was utilized in the present study for the optimization of the composite since it allows reduced
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number of experimental runs and easy control of factors.21, 25 Furthermore, it has been extensively
Recently, the direction of research has moved toward
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used in the experimental design and optimization processes of polymeric matrices where responses
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can be linked mathematically and statistically to the material composition.21, 25-26
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This study aims to find the optimum conditions to incorporate GO into a polymeric matrix
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composed by chitosan (CS) and polyethyleneimine (PEI), and crosslinked with glutaraldehyde
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(GLA). Compositions of GO and PEI, amounts of GLA and dip coating time in the CS solution
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were optimized based on two response variables, namely % Cr(VI) and % Cu(II) removals. An
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experimental matrix was generated based on an I-optimal design to establish the working region
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of the RSM. Obtained results were fitted into model equations in the form of quadratic equations.
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The statistical treatment based on residual and error analysis were carried to obtain significant
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models for Cr(VI) and Cu(II) removals. Numerically optimized coating parameters were
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experimentally validated and used to coat different commercially available filter matrices to select
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the most suitable filter platform for the coating. Based on the integrity of the coating when exposed
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to different water chemistries potential membrane filter materials were selected. The resulting
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coating was characterized and further tested for Cr(VI) and Cu(II) removals. The potential uptake
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mechanisms of the coating was also investigated.
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2. EXPERIMENTAL PROCEDURES
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2.1 Materials. GO used for the coating was synthesized using the modified Hummer’s
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method27 starting from graphite (
