The X-ray powder diffraction pattern of ZnO:AC composite is shown in Fig. 1. The identification of crystalline phase of ZnO was accomplished by comparison with JCPDS file (PDF: 800075) and there was no change in the ZnO phase after the hydrothermal experiment. The ZnO:AC (ZnO from 0.1 g to 0.5 g) and ZnO:AC (ZnO from 0.1 g to 1 g) was considered for BET and FTIR measurements respectively. Fig. 2 shows the FTIR spectra for commercial activated carbon and reagent grade ZnO. Fig. 3 shows the FTIR spectra for ZnO:AC(ZnO=0.1 g to 1 g). The FTIR spectra of ZnO:AC (0.1 g) to ZnO:AC (0.3 g) are similar to that of untreated activated carbon and on further increasing ZnO%, ZnO:AC (0.4 to 0.5 g), the gradual shift of FTIR absorption bands in the range of 400 – 1500 cm−1 towards ZnO can be noticed, which is more dominantly seen in ZnO:AC(1 g) (Fig. 3). The possible explanation for this is, when the ZnO% is low (ZnO:AC (< 0.5 g)), most of the ZnO particulates during the impregnation enter into the pores of the activated carbon and only fewer ZnO particles are deposited on the outer surface, which is not detected by the FTIR. But when the ZnO% is increased beyond 0.5 g (ZnO:AC (> 0.5 g)), the excess of ZnO that cannot enter the activated carbon pores remains in the system, which is detected by the FTIR as can be seen in the ZnO:AC (1 g) (Fig. 3). To confirm this, AC and ZnO were thoroughly mixed in a similar proportion (AC = 1 g and ZnO = 0.2 g) and FTIR was recorded (Fig. 4) for this mixture, which resembles the ZnO pattern. The FTIR bands in the region 400–1500 cm−1 of ZnO:AC (0.2 g) mixed and ZnO:AC (0.2 g) hydrothermally treated (Fig. 4), clearly indicate that the ZnO is available in the system and impregnation cannot take place without the hydrothermal treatment. The BET surface area measurement of ZnO:AC is represented in Fig. 5. The average specific surface area of the activated carbon is strongly dependent on the weight of ZnO. It is observed that upto ZnO:AC (0.2 g), it shows only a marginal decrease in the average specific surface area, beyond which it decreases rapidly. This is because of the blocking of pores by the excess ZnO particulates. It was then considered that 0.2 g of ZnO was optimum for impregnation. From the nitrogen gas adsorption (BET) and FTIR spectroscopic studies, it can be concluded that the ZnO particles are deposited in the macro- and mesopores of activated carbon blocking the micropores, which in turn decreases the surface area. High-resolution SEM studies have shown the impregnation of the ZnO particulates onto the carbon surface. Fig. 6 shows the external morphology of the ZnO:AC composites. Figs. 6a and b clearly show the ZnO particulates deposited on the surface and much in the pores of the activated carbon particle. Fig. 6d shows the enlarged portion of the pores. Fig. 6c shows the EDX spectrum of representative parts of the Fig. 6a and b.
The X-ray powder diffraction pattern of ZnO:AC composite is shown in Fig. 1. The identification of crystalline phase of ZnO was accomplished by comparison with JCPDS file (PDF: 800075) and there was no change in the ZnO phase after the hydrothermal experiment. The ZnO:AC (ZnO from 0.1 g to 0.5 g) and ZnO:AC (ZnO from 0.1 g to 1 g) was considered for BET and FTIR measurements respectively. Fig. 2 shows the FTIR spectra for commercial activated carbon and reagent grade ZnO. Fig. 3 shows the FTIR spectra for ZnO:AC(ZnO=0.1 g to 1 g). The FTIR spectra of ZnO:AC (0.1 g) to ZnO:AC (0.3 g) are similar to that of untreated activated carbon and on further increasing ZnO%, ZnO:AC (0.4 to 0.5 g), the gradual shift of FTIR absorption bands in the range of 400 – 1500 cm−1 towards ZnO can be noticed, which is more dominantly seen in ZnO:AC(1 g) (Fig. 3). The possible explanation for this is, when the ZnO% is low (ZnO:AC (< 0.5 g)), most of the ZnO particulates during the impregnation enter into the pores of the activated carbon and only fewer ZnO particles are deposited on the outer surface, which is not detected by the FTIR. But when the ZnO% is increased beyond 0.5 g (ZnO:AC (> 0.5 g)), the excess of ZnO that cannot enter the activated carbon pores remains in the system, which is detected by the FTIR as can be seen in the ZnO:AC (1 g) (Fig. 3). To confirm this, AC and ZnO were thoroughly mixed in a similar proportion (AC = 1 g and ZnO = 0.2 g) and FTIR was recorded (Fig. 4) for this mixture, which resembles the ZnO pattern. The FTIR bands in the region 400–1500 cm−1 of ZnO:AC (0.2 g) mixed and ZnO:AC (0.2 g) hydrothermally treated (Fig. 4), clearly indicate that the ZnO is available in the system and impregnation cannot take place without the hydrothermal treatment. The BET surface area measurement of ZnO:AC is represented in Fig. 5. The average specific surface area of the activated carbon is strongly dependent on the weight of ZnO. It is observed that upto ZnO:AC (0.2 g), it shows only a marginal decrease in the average specific surface area, beyond which it decreases rapidly. This is because of the blocking of pores by the excess ZnO particulates. It was then considered that 0.2 g of ZnO was optimum for impregnation. From the nitrogen gas adsorption (BET) and FTIR spectroscopic studies, it can be concluded that the ZnO particles are deposited in the macro- and mesopores of activated carbon blocking the micropores, which in turn decreases the surface area. High-resolution SEM studies have shown the impregnation of the ZnO particulates onto the carbon surface. Fig. 6 shows the external morphology of the ZnO:AC composites. Figs. 6a and b clearly show the ZnO particulates deposited on the surface and much in the pores of the activated carbon particle. Fig. 6d shows the enlarged portion of the pores. Fig. 6c shows the EDX spectrum of representative parts of the Fig. 6a and b.
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