TEMPO-oxidized pulp as an efficient and recyclable sorbent to remove paraquat from water

To enhance adsorption capacity for paraquat, paper pulp cellulose is particularly oxidized via the TEMPO-mediated oxidization to functionalize cellulose with carboxylates. The TEMPO-oxidized pulp (TOP) exhibited more than 20-time higher and 5-time higher adsorption capacity than the original paper pulp and activated carbon, respectively. The adsorption kinetics, isotherm and thermodynamics of paraquat to TOP are also determined and analyzed. The adsorption isotherm indicates that TOP can reach an adsorption capacity of 175 mg g(-1) at 20 A degrees C. Factors affecting the adsorption are also examined including TOP loading, initial concentration, temperature, pH and salts. TOP can also be regenerated by a simple washing using a highly concentrated NaCl solution and the regeneration efficiency was maintained above 90 % up to 4 cycles. These features indicate that TOP can be a high-capacity and reusable adsorbent to remove paraquat from water.