Preparation and characterization of radiation grafted fibrous adsorbent containing N-methyl-D-glucamine for boron removal

Abstract

Water contamination with boron is currently increasing due to its multiple uses in various chemical industries and this poses threats to the environment and human health. Removal of boron by ion exchange resin is the most suitable technology but it is challenged by high cost of resins and slow kinetics. To overcome this problem, a new fibrous adsorbent containing glucamine for removal of boron from solutions was prepared by radiation induced graft copolymerization (RIGC) of vinylbenzyl chloride (VBC) onto nylon-6 fibers followed by functionalisation with N-methyl-D-glucamine (NMDG). The best combination of grafting parameters required for achieving the highest degree of grafting (DG) was determined. The density of glucamine loaded in the adsorbent was tuned by optimisation of the reaction parameters using response surface methodology (RSM) employing Box–Behnken design (BBD). The obtained adsorbent was characterized using various materials and analytical research techniques (scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical tester) to confirm the incorporation of poly(VBC) and glucamine groups and to evaluate the impact of preparation procedure on the adsorbent’s physico-mechanical properties. The performance of the fibrous adsorbent under various conditions pertaining to equilibrium isotherms, kinetics and thermodynamics of boron adsorption from aqueous solutions were evaluated using relevant models. The DG was found to be a function of reaction parameters and could be tuned to 130% at 20 wt% VBC concentration in methanol, 300 kGy absorbed dose, 30 °C and 3 h. The optimum parameters for achieving a glucamine density of 1.7 mmol/g in the adsorbent are 10.6%, 81 oC, 47 min and 121% for NMDG concentration, reaction temperature, reaction time and DG, respectively. The deviation between the optimum experimental and predicted glucamine density is found to be 1.2% suggesting the reliability of RSM in predicting the yield and optimising the functionalisation reaction parameters. The boron adsorption equilibrium followed Redlich-Peterson isotherm. Moreover, the adsorption is governed by a film diffusion mechanism and occurs spontaneously. The results of this study suggest that a new fibrous adsorbent having a higher adsorption capacity and faster kinetics than commercial granular resin is obtained and has the potential application in boron removal from aqueous solutions.