Biosorption of Chromium from Aqueous Solution Using Chitosan

Adsorption experiment from aqueous solutions containing known amount of Cr （chromium） using chitosan was explored to evaluate the efficiency of chitosan as sorbent for Cr. Some variable parameters such as pH, reaction time and chitosan dosage were optimized. Under the optimum experiment condition, the effect of common ions on the adsorption of Cr （i.e., Na^＋, K^＋, Mg^2＋, Ca^2＋ for Cr（Ⅲ）, and Cl^-, NO3^-, SO4^2- for Cr（Ⅵ）） was also investigated. Furthermore, the sorption mechanism of Cr by chitosan was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained. In addition, to confirm the characteristics of the chitosan, the surface morphology of the biomass was determined by SEM （scanning electron microscope） and specific surface area analyzer （N2-BET （Brunaeur, Emmet and Teller））. Consequently, the following matters have been mainly clarified： （1） chitosan can be an efficient sorbent for Cr （both Cr（Ⅲ） and Cr（Ⅵ））; （2） the effect of common ions on the adsorption ofCr （Cr（Ⅲ） and Cr（Ⅵ）） was not significant under this experimental conditions; （3） adsorption isotherms using the chitosan can be generally described by Langmuir isotherm more satisfactorily for Cr. The adsorption may have occurred mainly by monolayer reaction; （4） the rates of adsorption were found to conform to pseudo-second order kinetics.

Removal of Chromium from Aqueous Solution Using Hybrid Membrane of Chitosan and Silicon Dioxide

Adsorption experiment from aqueous solutions containing known amount of chromium （Cr） using hybrid membrane of chitosan and silicon dioxide was explored to evaluate the efficiency of the membrane as sorbent for Cr（VI）. Some variable parameters such as pH, contact time and the dosage of the membrane were optimized. Adsorption isotherms of Cr（VI） onto the hybrid membrane were measured with varying initial concentrations under optimized condition. Furthermore, the sorption mechanism of Cr by the membrane was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained. The surface morphology of the membrane was determined by SEM （scanning electron microscope） for material characterization. The concentrations of Cr in solution are determined by ICP-MS （inductively coupled plasma mass spectrometry）. Hybrid membrane of chitosan and silicon dioxide can be an efficient sorbent for Cr（VI）.

Study on Removal of Cr(VI)from Aqueous Solution by Cross-Linked Chitosan

In this paper,the adsorbent for the removal of hexavalent Cr(Chromium)from aqueous solutions has been prepared by modifying chitosan composite with EP(Epichlorohydrin)or GA(Glutaraldehyde).The modified cross-linked chitosan was characterized by SEM(Scanning Electron Microscopy)and FT-IR(Fourier Transform Infrared Spectroscopy).Batch adsorption experiments were carried out to evaluate the adsorption of Cr(VI)by the cross-linked chitosan under different conditions.Furthermore,the sorption mechanism of Cr(VI)by the cross-linked chitosan was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained.The concentration of Cr in solution was determined by ICP-MS(Inductively Coupled Plasma Mass Spectrometry).The cross-linked chitosan can be an efficient sorbent for Cr(VI).

Contact parameter analysis and calibration in discrete element simulation of rice straw

Discrete element method was used to study and analyze the interaction between rice straws and between rice straw and agricultural machinery parts,thereby providing a scientific basis for post-harvest paddy field processing.Calibrations of rice straw-rice straw,rice straw-agricultural machinery part contact parameters(collision recovery coefficient,static friction coefficient and rolling friction coefficient)constitute an important prerequisite for the discrete element research process.In this study,the collision recovery coefficients of rice straw-steel and rice straw-rice straw were 0.230 and 0.357,respectively,which were calibrated by the collision method.The static friction coefficient and rolling friction coefficient of rice straw-steel were 0.363 and 0.208 respectively,which were calibrated by the inclined plate method and the slope method.The static friction coefficient and rolling friction coefficient of rice straw-rice straw were 0.44 and 0.07,respectively,which were calibrated by the split cylinder method.The paired t-test showed insignificant differences between calibration parameter simulation results and the physical test values(p>0.05).Taking the angle of repose that reflecting rice straw flow and friction characteristics as the evaluation index,the verification tests of the above calibration values indicated that the simulated angle of repose has no significant difference from the physical test value(p>0.05).The side plate lifting test on rice straw of different lengths showed no significant difference between the simulated angle of repose and the physical test value(p>0.05).This study can provide a basis for contact parameters choice in discrete element simulation analysis with rice straw-rice straw and rice straw-agricultural machinery parts as the research object.The calibration method can provide a reference for the contact parameter calibration of other crop straws.