In this work, preparation, characterization and nitrate removal ability of a chemically modified cellulose nanocrystal (CPTMS/CNC) were investigated for the first time. The FTIR, FESEM, EDX and TG analyses confirmed the successful modification of the cellulose nanocrystal (CNC) by 3-chloro propyl trimethoxysilane (CPTMS) and the thermal stability of CPTMS/CNC. The optimum removal efficiency (86.5%) occurred at initial pH of 7 and room temperature (~25°C) with an initial nitrate concentration of 20 mg/L, contact time of 10 min and CPTMS/CNC dosage of 3 g/L. The nitrate adsorption dropped noticeably in the presence of sulphate, followed by bicarbonate, chloride and phosphate, respectively. The kinetic adsorption data were fitted well with the pseudo-second-order kinetic model and the adsorption process involved two stages. The equilibrium adsorption data obeyed the Freundlich isotherm model. Thermodynamic analysis suggested a spontaneous and exothermic adsorption process with a decrease in random collisions at the solid-solution interface.

This study represents the first attempt to chemically modify wheat straw (WS) using 3-chloropropyltrimethoxysilane (CPTMS) and (1,4-diazabicyclo[2.2.2]octane) (DABCO). Field emission scanning electron micrographs (FESEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectra confirmed the successful morphological and structural modification of WS and the thermal stability of the modified WS (MWS). The MWS was used to remove nitrate from water. The optimum conditions of nitrate adsorption onto MWS were examined by conducting batch experiments. The results indicated that 85% of nitrate was removed under the conditions of initial nitrate concentration = 20 mg L−1, initial solution pH = 7, contact time = 10 min, MWS dosage = 2 g L−1 and temperature ≈ 25 °C. The kinetic adsorption data were best fitted to the general order model and the adsorption process occurred in three distinct stages. The equilibrium adsorption data were well described by the Langmuir isotherm. Additionally, separation factor values were smaller than 1, implying that the adsorption process was favorable. The presence of competing anions impeded the nitrate adsorption in the order of sulfate > chloride > bicarbonate> phosphate. Thermodynamic parameters suggested that the adsorption process was exothermic, feasible and spontaneous in nature. Overall, the MWS could achieve efficient removal of nitrate under the simplest operating conditions.

No abstract