| Phenols are toxic to humans and aquatic life;they create an oxygen demand in receiving waters.By increasing the industrial wastewaters,the demand for removal of organic compounds including phenol has been increased.Adsorption of phenol by different adsorbents has been investigated to find the relation between adsorption capacity and adsorbent characteristics such as surface area,and pore size distribution for separation applications in the drinking water concentration range.In this project,the adsorption and desorption behavior of phenol that existed in aqueous solutions,were determined using four commercial polymeric resins featuring aminofunctionalized groups fixed on their polystyrene-divinylbenzene matrix.These polymeric resins are named Lewatit VP OC 1065,D308,Purolite A110,and JT002.Furthermore,the application of high-pressure C02 as a solvent regenerant was studied.The amino-functionalized groups attached in the matrix of Lewatit VP OC 1065 displayed higher adsorption capacity and chemical affinity with phenol due to electrostatic attraction forming ionic bonding,giving a maximum adsorption capacity of 4ยท0.49 mg/g and removal efficiency of 95.46%.Regardless of D308,Purolite A110,and JT002 also possess amino-functionalized groups in less quantity,the adsorption capacities of phenol that these three resins showcased were 29.02 mg/g,22.61 mg/g,and 14.27 mg/g,respectively.Adsorption equilibrium results for phenol removal evaluated by Lewatit VP OC 1065,D308,Purolite A110,and JT002 have mostly suited well to the Langmuir isotherm model,interpreted that the current adsorption of phenol forms a monolayer coat around the surface of the matrix.Corresponding to the kinetic data results,the removal of phenol was acquired faster for Lewatit VP OC 1065 due to the larger quantity of aminofunctionalized groups present in its matrix.The results of the kinetic investigation manifested that the adsorption kinetics fit better the pseudosecond order kinetic model,indicating that between the amino-functionalized groups and phenol there is chemical adsorption.This phenomenon was similar for phenol removal using all four types of adsorbents.The desorption process using high-pressure CO2 was studied using 3 different pressures and 4 temperatures.It was determined that at a higher pressure and temperature,faster desorption occurred.During the desorption process,increasing the pressure can be interpreted as increasing the density of the gas,allowing more CO2 molecules to interact with the aminofunctionalized groups in the resin replacing the already adsorbed phenol.At the same time,increasing the temperature of the system produces a weakening between the amino-functionalized groups and phenol molecules producing a more efficient replacement of phenol by C02.The amino-functionalized groups in the resin have more selectivity for more acidic compounds,therefore C02 molecules are adsorbed by the resin,and phenol is dislodged in the wet system.The thermodynamics for the adsorption indicate a spontaneous,feasible,and endothermic process.Moreover,7 adsorption/desorption cycles were tested for Lewatit VP OC 1065 performing great stability.During the adsorption/desorption cycles,it is possible to observe a small decrease in the adsorption capacity of the resin.C02 molecules and amino compounds,at high temperatures,can react creating irreversible urea molecules((NH2)2CO),producing an inactivation of some amino-functionalized active sites. |
