# Fine Activated Carbon from Rubber Fruit Shell Prepared by Using ZnCl\({}_{2}\) and KOH Activation
## 3 Results  
### Characterization of RFSFACs  
Table 2 presents the proximate analysis results for the various RFSFAC products. As shown, the moisture content of the KOH-activated products increases from 16.76 to 23.51 wt.% as the impregnation ratio increases from 1:3 to 1:5. Similarly, the moisture content of the ZnCl\({}_{2}\)-activated products increases from 13.31 to 14.98 wt.%. Meanwhile, the fixed carbon content increases from 16.26 to 23.84 wt.% for the KOH products and 23.26 to 38.09 wt.% for the ZnCl\({}_{2}\) products. The greater moisture content of the RFSFAC products under a greater impregnation ratio implies that a stronger activator concentration is beneficial for increasing the surface area of the activated carbon, and hence for increasing the hygroscopic properties of the product [40]. Meanwhile, the higher fixed carbon content of the activated RFSFACs with a greater impregnation ratio reflects a corresponding reduction in the volatile and ash content of the products. In particular, the volatile content of the KOH-activated products reduces from 56.38 to 42.24 wt.% as the impregnation ratio increases from 1:3 to 1:5, while that of the ZnCl\({}_{2}\)-activated products reduces from 48.24 to 33.44 wt.%. The reduction in the volatile content arises since the activators degrade the surface structure of the activated carbon, and thus facilitate the easier removal of the volatile substances [41]. There is also a slight reduction in the ash level with an increasing activator concentration, i.e., from 10.59 to 10.41 wt.% for the KOH-activated products and 15.19 to 13.50 wt.% for the ZnCl\({}_{2}\) products. It is speculated that the reduction in the ash content is the result of a reaction between the activator and the minerals contained in the RFS raw material. It is noted that this inference is consistent with the findings of a previous study [41] which showed that the ash content produced during pyrolysis depends on both the amount and the composition of the mineral salts in the raw material. Referring to the EDS analysis results presented in Table 2, it can be observed that the KOH-derived RFSFAC has a carbon content from 72.29 to 78.40 at.%. By contrast, the ZnCl\({}_{2}\)-derived FAC has a higher carbon content from 65.94 to 81.83 at.%. In other words, while both RFSFACs have a high carbon content, ZnCl\({}_{2}\) yields an improved activation effect. The EDS analysis results additionally show that the RFSFACs activated using KOH contain relatively large amounts of potassium, while those activated using ZnCl\({}_{2}\) have relatively large contents of chlorine and zinc. Figure 1 shows the thermal decomposition behaviors of the carbonized RFSFC charcoal and RFSFAC products, respectively. For the RFSFC product, the mass remains approximately constant until 400 \({}^{\circ}\)C, and then rapidly decreases, almost to zero at a temperature of 650 \({}^{\circ}\)C. The rapid weight loss at temperatures from 400 to 650 \({}^{\circ}\)C is associated mainly with the formation of ash as a result of devolatilization. Comparing the weight loss behaviors of the activated RFSFAC products, it can be obsserved that the products activated using KOH (i.e., RFSFAC1-3) decompose more rapidly than those activated using ZnCl\({}_{2}\) (RFSFAC4-6). For the RFSFC activated with KOH, the mass loss can be explained as follows: A significant mass loss occurs at around 150 \({}^{\circ}\)C as a result of dehydration and moisture evaporation [42]. Then, the mass loss is around 70% of the total weight percentage at a temperature of around 450 \({}^{\circ}\)C. The weight loss is primarily attributed to the decomposition of activating agencies. [PERSON] et al. [42] explained that when the temperature is around 200 \({}^{\circ}\)C, KHCO\({}_{3}\) is rapidly decomposed to H\({}_{2}\)O and CO\({}_{2}\), leading to increased weight loss. At higher temperatures (e.g., from 700 to 900 \({}^{\circ}\)C), the mass continues to reduce due to the release of carbon oxide and potassium sublimation [43].