Single-step preparation of copper nanoparticle-enhanced activated carbon for anionic dye adsorption

Abstract

The utilization of zero-valent metals@activated carbon composites as adsorbents has shown significant potential. In this study, a one-step pyrolysis method using copper acetate and pomegranate peel waste in presence potassium hydroxide was used to prepare nanoscale copper supported on biomass-derived porous activated carbon (ZVCu@PAC) to apply as a promising adsorbent. ZVCu@PAC exhibited promising characteristics, boasting a high specific surface area (1211 m²/g), large total pore volume (0.547 cm³/g), and hierarchical porosity with uniformly dispersed nanoscale copper particles (4.52 nm). The adsorption capacity of ZVCu@PAC for anionic dyes exceeds that for cationic dyes. Naphthol blue black (NBB) as anionic dye was used as a model to examine the effects of pH, concentration, time, and temperature on the adsorption process. The kinetic and isotherm studies indicated that the pseudo-first-order and Freundlich models best-described adsorption onto PAC, while the Elovich and Langmuir models were more suitable for ZVCu@PAC. The Langmuir isotherm model revealed a significant enhancement in the maximum adsorption capacity of ZVCu@PAC, reaching 520.03 mg/g versus 311.45 mg/g for unmodified PAC. Through thermodynamic analysis, it was determined that the adsorption process is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0), indicating that it is driven by an increase in entropy and requires an input of energy. The ZVCu@PAC exhibited excellent reusability, maintaining its adsorption capacity for six consecutive cycles. It also demonstrated a high efficiency in removing mixtures of anionic/cationic dyes. This study demonstrates a simple method for improving activated carbon adsorption with metals nanoparticles, promoting progress in dye-contaminated water treatment.