| Giant reed (GR) is a well-known perennial herb, which has good resistance to environmental stress, such as drought, salinization, barrenness and so on. With the development of economy in our country, water eutrophication has become a serious environmental problem, and phosphorus is generally considered to be a limiting factor in water eutrophication. It is very important to remove phosphate for water remedation in our country.Giant reed (GR) was modified into giant reed quaternary amino anion exchanger (GR-QE) for the removal of phosphate by reacting with epichlorohydrin, ethylenediamine (EDA) and triethylamine in the presence of N, N-dimethylformamide (DMF). Factors like GR dosage, temperatures and volumes of organic liquid chemicals were used in single factor experiments and orthogonal experiments for determining optimal conditions, with phosphate removal efficiency as indicators. The results indicated that the optimal conditions obtained in the orthogonal experiments were consistent with those in the single-factor experiments. The optimal dosages of the reactants used in the preparation of GR-QE could be concluded as:GR: epichlorohydrin:DMF:EDA:triethylamine= 4 g:10 ml:5 ml:2ml:10 ml and the experimental temperature was selected at 60-70°C. The GR utilization on a large-scale was realized, and the dosage of EDA was considered as the key influential factor in the preparation of GR-QE. The physical and chemical characteristics of GR and GR-QE were examined by lots of instruments, such as scanning electronic microscope, element analysis instrument and FT-IR spectrometer. The results indicated that the physical and chemical characteristics of GR-QE had significant difference with those of GR. The surface of GR-QE was clearer and smoother in comparison with GR. IR spectrums of GR and GR-QE demonstrated an increase of amino groups in the structure of GR-QE and it was validated by the elemental analysis which indicated a significant increase of nitrogen content in GR-QE.The use of modified giant reed (MGR) as adsorbent to remove phosphate from aqueous solution was investigated. The dosage of MGR, pH of phosphate solution, thermodynamics and the effects of several factors on kinetics were studied in batch experiments. The results showed that MGR was particularly effective to remove phosphate, and that the effective pH for the phosphate removal was about 5. The adsorption capacities did not changed significantly as temperature changed so that it will be useful in the practical application. Three kinetic models have been evaluated to fit the experimental data. It was shown that the pseudo second-order model best described the adsorption kinetics of phosphate on MGR. The low activation energy of the adsorption suggested a physisorption process for phosphate adsorption. The equilibrium isotherm showed that the adsorption system was consistent with Langmuir equation. The negative values of standard free energy (△G) and enthalpy (△H) indicated that the adsorption of phosphate onto MGR was a spontaneous and exothermic process.The factors influencing dynamic adsorption and desorption were investigated and the re-adsorption effects of phosphate were tested. The results showed that the adsorption capacity of modified giant reed increased much, compared with giant reed. A shorter breakthrough time was found in a higher concentration of phosphate and the phosphate removal in solution decreased with increasing flow velocity. The effective pH for the phosphate removal was 5.0. 0.01mol/L NaCl, HC1 and NaOH solutions with 5 ml/min flow velocity had good desorption capacities and the adsorptive capacities decreased from 45.625 mg/g to 40.301 mg/g,38.197 mg/g and 35.268mg/g, respectively, after 10 dynamic desorptions. So the regenerated modified giant reed had excellent properties.
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