  This study explores a green pathway for urea synthesis using plasma-ice
interaction with gas mixtures of N2 + CO2 and NH3 + CO2. Electrical and optical
emission spectroscopy were employed to characterize the plasmas, revealing that
urea formation involves complex reactions driven by high-energy species,
producing reactive nitrogen and carbon intermediates that further react to form
urea. Physicochemical analyses of plasma-treated ice showed increased pH,
electrical conductivity (EC), and reduced oxidation-reduction potential (ORP).
Optimization of plasma process parameters (gas pressure, applied voltage, and
treatment time) was performed to enhance urea formation. Among these
parameters, plasma treatment time had the most substantial influence.
Increasing treatment time from 20 to 60 minutes significantly impacted
physicochemical properties: for N2 + CO2 plasma, pH increased by 21.05%, EC by
184.7%, and ORP decreased by 27.48%; for NH3 + CO2 plasma, pH increased by
27.37%, EC by 239.05%, and ORP decreased by 72.67%, respectively. The study
shows that NH3 + CO2 plasma produces a significantly higher concentration of
urea (7.7 mg L-1) compared to N2 + CO2 plasma (0.55 mg L-1). This is attributed
to the direct availability and reactivity of ammonia, which simplifies reaction
pathways and enhances intermediate formation. These findings highlight the
potential of plasma-ice interaction as an energy-efficient and environmentally
friendly method for urea synthesis, offering a sustainable alternative to
conventional processes.
