Facile Synthesis of the Polyaniline@Waste Cellulosic Nanocomposite for the Efficient Decontamination of Copper(II) and Phenol from Wastewater

**Background:** Wastewater contaminated with heavy metals and organic pollutants such as copper and phenol poses serious risks to human health and ecosystems. Copper is toxic and carcinogenic, accumulating in the liver and causing organ damage, while phenol is highly toxic to aquatic life and humans. Among various remediation technologies, adsorption is considered cost-effective and practical. Cellulose-based materials like waste tissue paper (WTP) are abundant and low-cost but suffer from high hydrophilicity, limiting pollutant uptake. Polyaniline (PANI) offers amine and imine functional groups suitable for pollutant binding but has poor processability. This study aimed to combine PANI with WTP to create a nanocomposite with enhanced adsorption capacity for Cu(II) and phenol.

**Methods:** Waste tissue paper was collected, sterilized, washed, dried, and exfoliated into fibers. The PANI@WTP nanocomposite was synthesized via single-step in situ oxidative polymerization: 1 g of exfoliated WTP was suspended in ethanol, sonicated, and mixed with aniline in HCl. Ammonium persulfate was added dropwise as an oxidant, and the mixture was stirred for 18 h in an ice bath. The resulting blue-green composite was filtered, washed, and dried. Characterization was performed using XRD, TEM, and FTIR. Batch adsorption experiments were conducted with 0.02 g of adsorbent in 20 mL of Cu(II) or phenol solutions at varying concentrations (10–800 mg/L), contact times (0–480 min), and pH (2–9). Residual concentrations were analyzed using a DR/6000 UV-visible spectrophotometer. Desorption and regeneration were tested over five cycles using 0.1 M NaOH and 0.1 M HCl. The adsorbent was also tested on synthetic tap and groundwater samples at 20 mg/L and 100 mg/L concentrations.

**Key Results:** The PANI@WTP nanocomposite showed significantly higher adsorption than WTP or PANI alone: 96.23 mg/g vs. 46 and 38 mg/g for Cu(II), and 74.3 mg/g vs. 30 and 38 mg/g for phenol at 100 mg/L. The point of zero charge (PZC) was 9.76. Optimal pH was 5.2 for Cu(II) and 3 for phenol. Adsorption capacity increased with initial concentration, reaching 397 mg/g for Cu(II) and 320 mg/g for phenol at 500 mg/L. Kinetic modeling showed that Cu(II) adsorption best fit the Elovich model (R² = 0.9485), while phenol adsorption best fit the pseudo-second-order model (R² = 0.9746). The calculated qe from pseudo-second-order was 396.41 mg/g for Cu(II) (experimental: 397 mg/g) and 328.37 mg/g for phenol (experimental: 320 mg/g). Isotherm modeling revealed that the Langmuir model best described both Cu(II) (R² = 0.9436, qm = 605.20 mg/g) and phenol (R² = 0.9647, qm = 501.23 mg/g) adsorption. The Freundlich n values were 2.2012 for Cu(II) and 1.8580 for phenol. Regeneration studies showed the adsorbent could be reused for five cycles with slight loss in capacity. In synthetic tap and groundwater tests at 20 mg/L, Cu(II) adsorption was 11.3 mg/g (tap) and 14 mg/g (groundwater); phenol adsorption was 5.14 mg/g (tap) and 5.19 mg/g (groundwater). At 100 mg/L, Cu(II) adsorption was 21 mg/g (tap) and 43.23 mg/g (groundwater); phenol adsorption was 27 mg/g (tap) and 13.23 mg/g (groundwater).

**Clinical Implications:** This study is not a clinical investigation. However, the findings have environmental health relevance: the PANI@WTP nanocomposite offers a low-cost, recyclable adsorbent for removing copper and phenol from contaminated water sources, potentially reducing human exposure to these toxic pollutants. The material's high adsorption capacity and reusability support its application in water treatment systems, particularly in resource-limited settings.