Kunquan Li

Equilibrium, kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre.

Activated carbon prepared from cotton stalk fibre has been utilized as an adsorbent for the removal of 2-nitroaniline from aqueous solutions. The influence of adsorbent mass, contact time and temperature on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data at different temperatures were fitted with the Langmuir, Freundlich, Tempkin, Redlich-Peterson and Langmuir-Freundlich models. The Langmuir-Freundlich isotherm was found to best describe the experimental data. The adsorption amount increased with increasing temperature. The maximum adsorption capacity of 2-nitroaniline was found to be 383 mg/g for initial 2-nitroaniline concentration of 200mg/L at 45 degrees C. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and Elovich models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption, and intraparticle diffusion was the rate-limiting step at the first 30 min for the temperatures of 25, 35 and 45 degrees C. FTIR and (13)C NMR study revealed that the amino and isocyanate groups present on the surface of the adsorbent were involved in chemical interaction with 2-nitroaniline. The negative change in free energy (Delta G degrees) and positive change in enthalpy (Delta H degrees) indicated that the adsorption was a spontaneous and endothermic process.

Adsorption of p-nitroaniline from aqueous solutions onto activated carbon fiber prepared from cotton stalk.

Activated carbon fiber prepared from cotton stalk was used as an adsorbent for the removal of p-nitroaniline (PNA) from aqueous solutions. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. The effect of experimental parameters such as pH, salinity and temperature on the adsorption was studied. The obtained experimental data were then fitted with the Langmuir, Freundlich and Redlich-Peterson models to describe the equilibrium isotherms. The kinetics rates were modeled by using the pseudo-first-order and pseudo-second-order equations. The results indicated that cotton stalk activated carbon fiber (CS-ACF) is an effective adsorbent for the removal of PNA from aqueous solutions. The maximum adsorption capacity of 406 mg g(-1) was achieved at the initial PNA concentration of 200 mg L(-1). The optimum pH for the removal of PNA was found to be 7.6. The presence of ammonium chloride proved to be favorable for the process of adsorption. The adsorption amount decreased with increasing temperature. The Redlich-Peterson model was found to best represent the equilibrium data. The kinetic data followed closely the pseudo-second-order equation. Thermodynamic study showed the adsorption was a spontaneous exothermic physical process.

Gas-liquid hybrid discharge-induced degradation of diuron in aqueous solution.

Degradation of diuron in aqueous solution by gas-liquid hybrid discharge was investigated for the first time. The effect of output power intensity, pH value, Fe(2+) concentration, Cu(2+) concentration, initial conductivity and air flow rate on the degradation efficiency of diuron was examined. The results showed that the degradation efficiency of diuron increased with increasing output power intensity and increased with decreasing pH values. In the presence of Fe(2+), the degradation efficiency of diuron increased with increasing Fe(2+) concentration. The degradation efficiency of diuron was decreased during the first 4 min and increased during the last 10 min with adding of Cu(2+). Decreasing the initial conductivity and increasing the air flow rate were favorable for the degradation of diuron. Degradation of diuron by gas-liquid hybrid discharge fitted first-order kinetics. The pH value of the solution decreased during the reaction process. Total organic carbon removal rate increased in the presence of Fe(2+) or Cu(2+). The generated Cl(-1), NH(4)(+), NO(3)(-), oxalic acid, acetic acid and formic acid during the degradation process were also detected. Based on the detected Cl(-1) and other intermediates, a possible degradation pathway of diuron was proposed.