Two kinds of cotton linter-based adsorbents were synthesized by grafting dimethylaminoethyl methacrylate (DMAEMA) on cotton linter via radiation grafting polymerization, followed by further quaternization (QCL) or protonation (PCL). The effect of radiation dose and monomer concentration on grafting yield was optimized. The synthesized adsorbents were characterized by Fourier transform infrared spectrometry (FT-IR), Thermogravimetric Analysis (TGA), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The adsorption behaviors of the two adsorbents toward humic acid (HA) were investigated and discussed. pH effect studies showed that QCL was pH-independent, whereas PCL was just suitable for HA adsorption with pH < 6. The adsorption kinetics of the PCL and QCL adsorbent for HA removal were better described by pseudo-second-order kinetic mode and reached equilibrium in 40 min. The adsorption isotherms of the PCL and QCL adsorbent were well fitted with both Langmuir and Freundlich isotherm models, for which adsorption capacity reached 250 mg/g and 333 mg/g at pH 6, respectively. XPS analysis revealed the ratio of two amino group species at different pH, suggesting that the interaction mechanism of the adsorbent and HA was electrostatic adsorption.Keywords:cotton linter;humic acid;adsorption;radiation grafting
The complex and diverse forms of boron in aqueous solutions have presented a major challenge for boron separation. Boron can be chemically complexed with polyols to achieve the purpose of separation. It is of great significance to clarify the mechanism of polyol ligand capturing boron anion for optimizing the best ligand. The facile environmentally friendly functionalization of cotton linter polymer with amino-polyol was successfully demonstrated and resulted in essential polyhydroxy ligands containing amines for strong interactions with boron. The adsorption capacity of the boron adsorbents with the most –OH and N is up to 27.88 mg/g. The presence of the N, high vicinal diol content, and the branched structure all have a positive effect on the complexation efficiency. Optimization of the ligand structure is helpful to increase the boron uptake and it is of great significance to design the best adsorbent for boron separation from salt lake brine.
Quaternary ammonium salt type cotton linter (QCL) was synthesized by radiation grafting of dimethylaminoethyl methacrylate (DMAEMA) onto cotton linter and subsequent quaternization. Batch and column adsorption experiments were used to evaluate the adsorption behaviors of the QCL for phosphate. The adsorption kinetics of QCL for phosphate were well obeyed pseudo-second-order mode. The adsorption isotherms were well fitted by Langmuir, Temkin, and Dubinin–Radushkevich model. Column experiments showed that the breakthrough curves were dependent on the inlet concentration and flow rate but independent on space velocity. Moreover the QCL can be effectively regenerated for further repeated use at least 10 cycles. And QCL exhibited good selective adsorption for phosphate. Such high adsorption and desorption efficiency of QCL made it employing for phosphate adsorption in practical application.
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