Adsorption isotherms, kinetics and thermodynamics of nitrate and phosphate in binary systems on a novel adsorbent derived from corn stalks

Novel adsorbents from raw corn stalks (RCS) were synthesised after cellulose isolation followed by modification with epichlorohydrin, N,N-dimethylformamide, pyridine and diethylamine. The MCCS (modified cellulose from corn stalks) products were characterised by thermogravimetric analysis, elemental analysis, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR); moreover, the adsorption characteristics of nitrate and phosphate on MCCS were investigated in binary systems using batch adsorption procedures. The mass loss of RCS and MCCS may be divided into three stages and the modification reaction increased the stability of samples. The surface of MCCS was rougher than that of RCS and amine groups were successfully loaded onto MCCS, as shown by elemental analysis results and FT-IR spectra. The pseudo-second order kinetics equation and Langmuir isotherm could well describe the adsorption process, and the maximum adsorption capacities (298 K) of nitrate and phosphate on MCCS as calculated from the Langmuir isotherm were 13.6054 and 22.8833 mg/g, respectively. The obtained thermodynamic parameters indicated the spontaneous and exothermic nature of adsorption.