Abstract
A water filter was fabricated from a mixture of KMnO4 modified kapok carbon fiber, zeolite, bentonite and kaolinite clay for Fe3+ removal and water hardness treatment. The effects of amount of KMnO4 modified kapok carbon fiber (30-60 wt%), zeolite (20-40 wt%) and sintering temperature (500-700°C) on the properties of sintered products were evaluated. The best of sintered products were tested for treatment of solutions with 5 mg L-1 Fe3+ and 40-200 mg L-1 total water hardness. The results show that the physical properties of the sintered products were affected by the contents of KMnO4 modified kapok carbon fiber and sintering temperature. The linear drying shrinkages of the mixture of raw materials increase with increasing content of modified kapok carbon fiber amounts due to the effect of water amount used for mixing process. Furthermore, firing shrinkages of sintered products increased with increasing sintering temperature for the same ratio of raw materials. Finally, the firing shrinkages and density of sintered products decrease with increasing content of the modified kapok carbon fiber at constant sintering temperature. It was shown that the sintered product made with 40 wt% of KMnO4 modified kapok carbon fiber and sintered at 600°C is suitable for filter fabrication. The KMnO4 modified kapok carbon fiber filter could adsorb 5-6% more Fe3+ at equilibrium than filter made with kapok carbon fiber. The Fe3+ was removed by adsorption and precipitation processes. The Fe3+ adsorption process of modified kapok carbon fiber filter was fitted to the Langmuir model with maximum adsorption capacity of 53.76 mg g-1. For hardness removal, the Ca2+, Mg2+ and HCO3ˉ ions removal capacities from solutions of total hardness in the range 40-200 mg L-1 by modified kapok carbon fiber filter are 4.49-19.21 mg g-1 for Ca2+, 1.55- 5.31 mg g-1 for Mg2+ and 28.1-123.5 mg g-1 for HCO3ˉ, respectively.
Highlights
Porous ceramics have been widely used for separation applications where they are valued for their thermal resistance, structural stability and mechanical strength (van Garderen et al, 2011)
The firing shrinkage percentages of sintered products increase with increasing sintering temperature for the same ratio of raw materials (Table 2)
This is because the mixture of raw materials containing 60 wt% of KMnO4 modified kapok carbon fiber could not maintain the form of the sintered products as it does not have any strong binding materials in the structure (Görhan and Şimşek, 2013)
Summary
Porous ceramics have been widely used for separation applications where they are valued for their thermal resistance, structural stability and mechanical strength (van Garderen et al, 2011). Activated carbon has been widely used as an adsorbent for the removal of organic and inorganic pollutants from water and wastewater. The application of activated carbon in adsorption processes mainly depends on its surface chemistry and pore structure (Bhatnagar et al, 2013). Potassium permanganate is a substance that has been used for activation of carbon and water treatment (Han et al, 2013). Permanganate ion (MnO4-) from KMnO4 is transformed into MnO2 by the redox reaction in presence of C and water as shows in Equation 1 (Mu et al, 2015):
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