Overview
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- and a constant agitation speed for all adsorbents. The maximum Cr(VI) removal by K-CNTs (83.04%)
- occurred at pH 4 and 25 °C and at a constant agitation speed. Zn-CNTs achieved up to 79% removal
- efficiency at pH 2. However, at neutral pH (8), only K-CNTs maintained a high removal capacity (97%),
- whereas the other adsorbents exhibited an approximately 53% decrease in removal efficiency. The
- Cr(VI) removal efficiency reached 95% and 32.7% after five adsorption/desorption cycle tests for K
- and Zn-CNTs, respectively, at pH = 8, and K-CNTs achieved 91% removal after six cycles, which is
- zinc (Zn), were examined33. The results suggest that the average Cr concentration is 0.153 ± 0.175 mg/L, which
- lifetime carcinogenic risk (LTCR) estimate for Cr vulnerability in infants ranged from 0 to 2.14 × 10−4, indicating
- Graphite powder (99.95% metal basis, ≥ 44 μm) and short multiwalled carbon nanotubes (CNTs) (95% metal
- functionalized CNTs. Potassium hydroxide (KOH) (M, 0.02% K) and zinc acetate (ZnAC2) were obtained from
- Laboratory (Ilorin, Nigeria). Sodium hydroxide (NaOH) (M, 0.02% K), concentrated HCl (Scharlau, 38%
- impurity), 1% H3PO4, acetone, concentrated H2SO4 and deionized water were obtained from the Industrial
- dissolved in 30 g of water to yield a 3-weight% dispersion. After 30 min of stirring, 1 g of KOH powder was added
- Previous studies on adsorbent modification revealed that impregnation at 7 wt% resulted in the best performance
- A stock solution of chromium(VI) (10 mg/L) was prepared by dissolving 0.028 g of potassium dichromate
- in 1000 mL of deionized water to yield a 10 ppm solution. First, 1 M HCL–hydrochloric acid (Scharlau, 38%
- NaOH with 200 mL of deionized water. When refrigerated, the solution was stable for one month. First, 0.5%
- A 1000 mL round-bottom flask was used to produce a 1 mg/L Cr(VI) solution. A total of 20 mL of this solution
- washed, soaked in 1% H2SO4, rinsed, and dried in an oven.
- contaminated water was used, along with initial concentrations of 0.2, 1, 5, 10, 20, 30, and 40 mg/L, to examine
- of the samples were observed via thermogravimetric analysis (TGA) at 20 mL/min, a temperature range of 25–
- A total of 100 µL of 1 M H3PO4 was added to 20 mL of the sample, followed by 400 µL of 0.5% DPC, and the
- than 20 mg, the removal efficiency gradually increased and then plateaued. This means that above a certain
- maximum removal efficiencies at all dosages. They achieved 85–90% removal at high dosages. These CNTs are
- more efficient than activated carbon materials. The CNTs exhibited good performance, achieving up to 85%
- activated carbon. AC-1 is moderately efficient, achieving up to 80% removal at high dosages, which is superior
- an average of 70–75% of the material even when higher dosages are used, reflecting a lower adsorption capacity
- adsorption is due to the interaction between ions in the mixture and the generated composite40. Cr(VI) (1 mg/L)
- Figure 5b shows that the chromium RE decreased from 89 to 74% when the pH increased from 2.0 to 8.0 for
- pH ranges (pH 2–6). CrO42+ is the main ionic species above pH 6.0. The greater chromium RE at lower pH
- The chromium (VI) adsorbent dose (50 g/20 mL), starting concentration (1–20 mg/L, pH 2 and 4.0), temperature
- At initial Cr(VI) concentrations less than or equal to 1 mg/L, the percentage removal was greater than 90%;
- excellently, with removal percentages above 70–80%. This implies that at lower contaminant levels, there are
- its efficiency is more than 70%, i.e., it has good adsorption capacity. Zn-CNTs are slightly less effective than
- Fig. 5. (a) Effect of adsorbent dosage on chromium removal. iniConc. of 1000 ppb/20 mL, a T of 25 °C, and
- ppb, pH of 2, T of 25 °C, D of 50 mg/20 mL, time of 60 min. (c) Effect of contact duration on the residual
- chromium content. iniConc. of 1000 ppb/20 mL, a T of 25 °C, and a dosage of 50 mg. (d) Effect of varying the
- The Cr(VI) removal efficiency reached 95% and 32.7% after five adsorption/desorption cycle tests for K- and Zn-
- CNTs at neutral pH, i.e., pH = 8, and K-CNTs achieved 91% removal after 6 cycles, as shown in Fig. 6, which is
- to 13% at pH = 8 after approximately two adsorption‒desorption cycles. The chemically grafted alkaline groups,
- agitation speed, initial Cr(VI) concentration of 200 ppb, and 10 mg of adsorbent at a temperature = 25 °C and
- At 25 °C, 99% of the Cr(VI) was adsorbed in just 2 min at 200 ppb, and the K-CNTs demonstrated highly
Methods (brief)
- the adsorption processes in the polluted water samples, both before and after treatment. The results
- 1Department of Civil Engineering, Landmark University, Omu-Aran, Nigeria. 2Department of Civil Engineering,
- While examining particular heavy metals (HMs) and the dangers they pose in groundwater samples in
- Landmark University’s Industrial Chemistry Department for use in the impregnation/functionalization of
- of Landmark University. Diphenylcarbazide (Merck) was purchased from the Central Research and Diagnostic
- Chemistry and Biochemistry Department of Landmark University.
- Cr(VI) solution was adjusted to 2, and 20 mL samples were added to 24 conical flasks to examine the impact of
- 25 °C (20, 40, 60, 80, 100, 120, 140, 160, 180, 200, and 240 min). The samples were subsequently collected for
- sample were studied by scanning electron microscopy (SEM S-4800, HITACHI, Japan). Additionally, the chemical
- of the samples were observed via thermogravimetric analysis (TGA) at 20 mL/min, a temperature range of 25–
- 600 °C, and a sample mass of 1 g. In addition, the chemical and electronic states of the atoms in the adsorbent,
- A total of 100 µL of 1 M H3PO4 was added to 20 mL of the sample, followed by 400 µL of 0.5% DPC, and the
- mixture was incubated for at least 5 min before measurement via a UV‒visible spectrophotometer. The sample
- a VIVOSUN digital pH meter. Briefly, 0.40 g of each adsorbent sample was added to 20 mL of distilled water
- XPS spectra collectively indicate that all the samples are carbonaceous but have undergone different surface
- on the thermal stability of each sample. The peak at approximately 300 °C suggested a significant thermal
- transition in all the samples, which could be due to desorption, decomposition, or oxidation reactions. The
- in water samples. Environ. Monit. Assess. 157 (1–4), 575–582. https://doi.org/10.1007/s10661-008-0557-2 (2009).
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