Alternative methods of aqueous chromium removal have been of great research interest in recent years

Overview

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Key numbers

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• drinking water is only 0.1 ppm. Cr can be found in many oxidation forms; Cr (VI) being the most toxic and solu-
• (<45 µm) purchased from Sigma Aldrich. Polymeric materials, CS (low molecular weight), PEI (50% (wt/wt%)
• in water, avg. MW 750,000), and crosslinking agent GLA (25% (w/w%) in water) were purchased from Sigma
• Aldrich. To prepare the solutions containing Cr (VI), we used potassium dichromate (K2Cr2O7, crystals, 99.8%
• sodium hydroxide (NaOH, ACS reagent, ≥ 97% assay, pellets) and hydrochloric acid (HCl, ACS reagent, 37%
• position suggested by Perez et al.3. Briefly, a solution of CS-PEI-GO containing 2.0% CS, 2.0% PEI and 1500 ppm
• the pH became neutral. Then, the CS-PEI-GO beads were crosslinked with 2.08% glutaraldehyde (GLA) for
• were measured with 100 mg/L of each sample in DI water at pH 3.
• and used for the batch treatment with 50 mL of 100 ppm Cr (VI) solution (pH~3). The natural pH of the Cr (VI)
• concentration of 100 ppm to account for the amount of GO in the actual beads. After 24 hours of dynamic contact
• In the present study, after successful synthesis of the nanomaterials, they were exposed to 100 ppm Cr(VI)
• Cr (VI) solution. Experiments were performed at pH~3 with 100 ppm Cr (VI).
• Cr (VI) 70% 46% 77% 41%
• Cr (III) 30% 54% 23% 59%
• Table 1. Percentage abundance of Cr (VI) and Cr (III) based on the area of the fitted XPS peaks.
• for adsorption of Chromium17–19. Using a higher initial concentration of Cr(VI) (100 ppm) allowed us to achieve
• the XPS peak. Based on Table 1, the type of materials influenced the abundance of Cr (III) produced. The reduc-
• chromium (Figure S3). The different chemical species range from CrO4 2− at pH above 6 through HCrO4 − and
• ymer beads. For the unused beads in DI water, we can see positive surface charge density, as shown in Table S1.
• groups available on CS beads and the changes in the abundance of functional groups (Table 1), the following
• does not seem to be affected by the Cr adsorption. Table 2 shows the % of the different functional groups involved
• -OH peak in CS reduced to 46%, the peak attributing to the C=O, which is at 288.2 eV, increased from 5% to 10%
• Experiments were performed at pH~3 with 100 ppm Cr (VI).
• Ultimately, this led to a higher Cr (VI) signal, as shown in Table 1. This observation also agrees with the more sig-
• Table 2. Percentage abundance of different bonds based on the area of the fitted XPS peaks for the unused and
• performed at pH~3 with 100 ppm Cr(VI).
• seen by the more pronounced Cr (III) signals in the CS-PEI-GO as shown in Table 1, which clearly indicates the
• as shown in Fig. 2 and Table 2. Compared to CS and CS-PEI, the peak at 288.3 eV, which was attributed to C=O,
• 286.7 eV as shown in Fig. 2 and Table 2 compared to the control beads. As presented in Table 1 and Eqs. (7–9), the
• diagram for chromium, Table S1 showed the ζ-potential measurements, Figures S4 and S5 showed the ATR-FTIR

Methods (brief)

• in the NaOH bath and collected after about 30 minutes. The beads were washed several times with DI water until
• were performed in a Zetasizer Nano (Malvern) using the zeta potential transfer standard DTS 1235. The samples
• were measured with 100 mg/L of each sample in DI water at pH 3.
• in the redox mechanisms. As it is observed for all the samples, a conversion from –OH to carbonyl group is
• Sample Condition C-OH C=O C-C/ C=C C-NH2

Implications

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Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Shellfish (shrimp, crab, lobster, clams, oysters, mussels)
• Cadmium
• Chromium

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Update history

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