Fig. 4.

Effect of sulfite on (a) TCE degradation and (b) •OH radical accumulation. The degradation conditions for (a) are based on 198 μM initial TCE concentration, pH 4, 13.7 mg/L Fe²⁺, 1 g/L Pd/Al₂O₃ and 10 mM Na₂SO₄ background electrolyte. The reaction conditions for (b) are the same as for (a) except that no TCE was included. Lines and curves in (a) refer to pseudo-zero-order and pseudo-first-order kintic fittings, respectively. Pseudo-zero-order reaction kinetics is given by C_t = C₀−k₀t, where t is the reaction time (min), k₀ is the zero-order rate constant (μM/min), and c₀ and c_t are the concentrations (μM) at times of t = 0 and t = t, respectively. Pseudo-first-order reaction kinetics is expressed as ln(C_t/C₀) = k₁t + b, where b is a constant and k₁ is the first-order rate constant (min⁻¹).