The application of polyaniline (PANI) in flexible electronic devices has received increased attention due to its environmental stability, electrical conducting properties, and ease of production. While the electrical conductivity of a PANI film can be altered by modifying the number of PANI layers, this study aims to compare two techniques, namely ex-situ and in-situ, for the fabrication of PANI multilayer film. For the ex-situ technique, PANI was formed separately before being drop-casted on a filter paper; on the other hand, for the in-situ technique, polymerization of aniline into PANI and attachment of PANI on a filter paper was allowed to occur simultaneously. In both techniques, humic acid was used as the bridging agent. Results showed that the in-situ direct growth technique produced PANI multilayer film with good uniformity, lesser cracking, and detachment. On the other hand, the ex-situ drop-casting technique resulted in PANI film with very poor uniformity, irregular thickness, and severe detachment.

Adsorption has been a feasible process to remove dye molecules from water resources. However, some of the proposed adsorbents required high temperature to be synthesized or hard to be separated towards the end of their applications. Realizing this, this study aims to fabricate Fe3O4-decorated sand that does not require high temperature in production. More importantly, the attached Fe3O4 nanoparticles provide intrinsic magnetic properties to ease the subsequent separation. The ability of this adsorbent to remove methylene blue (cationic dye), tartrazine (anionic dye), and disperse yellow 3 (non-ionic dye) at different medium pHs were investigated. Results showed that the Fe3O4-decorated sand performed better in dye removal as compared to the pure sand counterpart. In specific, sand doped with 5000 mg/L of Fe3O4 successfully removed 75.01 % of methylene blue, as compared to the 68.01 % achieved by using pure sand alone. It was also found that the effectiveness of dye adsorption and desorption strongly depends on the medium pH mostly due to the amphoteric nature of the Fe3O4 nanoparticles. The desorption of methylene blue, tartrazine, and disperse yellow 3 from the adsorbent best to be done using 30 % v/v acetone, 0.1 M NaOH, and 30 % v/v ethanol, respectively. Additionally, it was found that this adsorbent can be effectively separated using either high or low gradient magnetic fields.

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