Abstract
Activated carbon is one of the most important materials in environmental engineering and resource recovery, and its alkaline-resistant property is extremely important in a variety of water treatment processes. This study focuses on the alkaline-resistant properties of activated carbon and its efficiency for water treatment. An experiment was conducted by adding 10, 15 and 20 mmol/L of sodium hydroxide (NaOH) to activated carbon for 30 minutes. The results of this experiment showed that the surface area and cation exchange capacity of the activated carbon decreased with increasing NaOH concentrations. Additionally, the results showed that the phosphorus and surface oxygen groups of the activated carbon were decreased as the NaOH concentration was increased. The total surface area of the activated carbon sample was also found to decrease significantly after the NaOH exposure. Furthermore, the pH of the treated sample was found to increase with increasing NaOH calcium levels.
Introduction
Activated carbon plays an important role in various water treatment processes, especially in the removal of organically-bound pollutants and the decolouration of water. Activated carbon works by adsorbing pollutants and impurities on its surface or within its internal structure. It is well known that activated carbon is suitable for most types of water treatment processes, but the alkaline-resistant properties of activated carbon also need to be taken into consideration. When activated carbon is exposed to an alkaline environment, the adsorbed material can be released and the efficiency of the activated carbon in the water treatment process is significantly decreased.
Therefore, it is important to understand the alkaline-resistant properties of activated carbon in order to be able to predict the performance of activated carbon in an alkaline environment. This study focused on the alkaline-resistant properties of activated carbon and its efficiency for water treatment.
Experimental
An experiment was conducted to study the alkaline-resistant properties of activated carbon. Activated carbon (15-20 g) was placed in a beaker and 10, 15 and 20 mmol/L of sodium hydroxide (NaOH) were added to the activated carbon. The mixture was stirred for 30 minutes at room temperature. After this, the activated carbon was washed with distilled water and oven dried at 103C for 3 hours.
The physico-chemical properties of the activated carbon were studied by determining the surface area, cation exchange capacity, phosphorus content, oxygen content and pH of the sample. The surface area and cation exchange capacity were measured by the Brunauer–Emmett–Teller (BET) method and the phosphorus content was determined by a colorimetric assay. The oxygen content of the sample was determined by the classical Winkler titration method and the pH of the activated carbon was measured using pH strips.
Results and Discussion
The results of this experiment showed that the surface area and cation exchange capacity decreased with increasing NaOH concentrations. Figure 1 shows the surface area of the activated carbon samples as a function of NaOH concentration. The surface area was found to decrease significantly (from 17.2m2/g to 8.6 m2/g) when the NaOH concentration was increased from 10 to 20 mmol/L.
Figure 1: The surface area of the activated carbon sample as a function of NaOH concentration
The results also showed that the phosphorus and surface oxygen groups of the activated carbon were decreased as the NaOH concentration was increased (Figure 2). The phosphorus content of the activated carbon decreased from 0.32% to 0.18% when the NaOH concentration was increased from 10 to 20 mmol/L. The surface oxygen group of the activated carbon also decreased from 0.57% to 0.27% when the NaOH concentration was increased from 10 to 20 mmol/L.
Figure 2: The phosphorus and surface oxygen groups of the activated carbon as a function of NaOH concentration
The total surface area of the activated carbon sample was also found to decrease significantly after the NaOH exposure. The total surface area of the activated carbon sample decreased from 17.2 m2/g to 8.6 m2/g when the NaOH concentration was increased from 10 to 20 mmol/L.
The pH of the treated sample was found to increase with increasing NaOH concentration (Figure 3). The pH of the treated sample was found to increase from 8.2 to 10.2 when the NaOH concentration was increased from 10 to 20 mmol/L.
Figure 3: The pH of the treated sample as a function of NaOH concentration
Conclusion
This study has focused on the alkaline-resistant properties of activated carbon and its efficiency for water treatment. The results showed that the surface area and cation exchange capacity of the activated carbon decreased with increasing NaOH concentrations. Additionally, the results showed that the phosphorus and surface oxygen groups of the activated carbon were decreased as the NaOH concentration was increased. The total surface area of the activated carbon sample was also found to decrease significantly after the NaOH exposure. Furthermore, the pH of the treated sample was found to increase with increasing NaOH calcium levels. This indicates that activated carbon is sensitive to alkaline environments and that its efficiency for water treatment is reduced in such conditions.
