Sorption Features of Polyurethane Foam Functionalized with Salicylate for Chlorpyrifos: Equilibrium, Kinetic Models and Thermodynamic Studies

Abstract

Commercial polyurethane foam was treated with salicylate salt to synthesize PUFSalicylate (PUFS) as a novel, promising, stable and inexpensive adsorbent for chlorpyrifos (CPF) extraction. The properties of PUFS were investigated using UV–Vis spectroscopy, apparent density, FTIR spectroscopy, pHZPC, BET surface area, elemental analysis, TGA and DTG tests. Batch experiments were performed for the sorption of CPF under different salicylate concentrations, pH, shaking time, ionic strength, agitation speed, sorbent mass, batch factor and initial concentration of CPF. The results confirmed that 97.4% of CPF in a 25 mL solution, 10 μg/L concentration, could be retained by only 0.3 mg of PUFS (1:105mass ratio of PUFS: solution). In addition, the maximum capacity of PUFS for the sorption of CPF was 1249.8 μg/mg (3.9 × 10−5 mol/g) within 180 min. The negative values of ΔH° and ΔG° indicated that the sorption of CPF onto PUFS is an exothermic spontaneous process (favorable). The calculated data from the experimental procedures fitted perfectly with Freundlich isotherm (R2 = 0.9952) and the kinetic Equation of pseudo-second order. In addition, the R2 value in the Elovich Equation recorded higher when compared to the Morris–Weber and Bangham Equations; hence, the pore diffusion is not the rate-determining step. Thus, the use of PUFSalicylate for the removal of chlorpyrifos contaminations from agriculture runoff is applicable.