| Diverse of wastewater discharged from industries contained heavy metals came into notice due to their toxic effect to human beings and other living things. Dealing with wastewater is of great concern. In this paper, we mainly researched the preparation of cellulose/collagen beads, and its adsorption ability to heavy metals, such as Cu(Ⅱ), Pb(Ⅱ), Ni(Ⅱ), Zn(Ⅱ) and Cr(Ⅲ).Firstly, we selected ionic liquids as solvent to prepare cellulose/collagen air-dried beads (CCB) with the mass ratio1/1,3/1,6/1, and then researched its adsorption ability of Cu(Ⅱ). Results revealed that when the mass ratio is1, the amount of adsorption was maximum, valued0.51mmol/g. The favorite condition is pH4.8,30min. Desorption with0.1mol/L HCl, almost all of the Cu(Ⅱ)can be desorbed from adsorbents. However, the fast rate of losing water in air which contributes to the denser structure, thus, the amount of adsorption in practice is lower as0.081mmol/g.Hydrogel is a three-dimensionally crosslinked network with hydrophilic network. Therefore, hydrogel bead with greater specific surface area, are the most promising materials to remove heavy metals. Biodegradable collagen/cellulose hydrogel beads (CCHB), was prepared by reconstitution from a1-butyl,3-methylimidazolium chloride ([C4mim]Cl) solution. The adsorption properties of the CCHB for Cu(Ⅱ) ion or Pb(Ⅱ) ion removal from aqueous solutions were investigated and compared with those of cellulose hydrogel beads (CHB). The effect of initial pH, contact time, initial heavy metal ions concentration, solutions temperature, co-anions in solution and different heavy metals at a constant of shaking speed and adsorption beads size was studied. The CCHB have a three-dimensional macroporous structure whose amino groups are believed to be the main active binding sites of heavy metal ions. The equilibrium adsorption capacity (qe) of the CCHB is greatly influenced by the collagen/cellulose mass ratio, and steeply increases until the collagen/cellulose mass ratio exceeds2/1. The maximum adsorption is obtained at pH6,240min for Cu(Ⅱ), pH4.2,360min for Pb(Ⅱ). The qe increases with increased initial concentration of the solution. Results suggest that the equilibrium adsorption was described by the Langmuir model. Based on Langmuir isotherms, the maximum adsorption capacity (qm) of CCHB3(collagen/cellulose mass ratio of3/1) is1.06mmol/g for Cu(Ⅱ),1.598mmol/g for Pb(Ⅱ) at293K. The CCHBs maintain good adsorption properties after the fourth cycle of adsorption-desorption. Co-anions has little effect on the adsorption of Pb(Ⅱ), the selectivity of Pb(Ⅱ) was much higher than other heavy metals studied. The kinetic processes of adsorption onto CCHB were described in order to provide a more clear interpretation of the adsorption rate and uptake mechanism. The overall kinetic data was acceptably explained by a pseudo second-order rate model. We also researched thermodynamics to evaluate the thermodynamic property of the adsorption, ΔG0and ΔH0specify the spontaneous and endothermic nature of the reaction. The adsorption takes place with an increase in entropy. Nevertheless, these materials still existed more or less defects such as poor mechanical strength, and poor acidic resistance which may limit to its application.Chitosan is a kind of very good biological crosslinking agent. Chitosan blended cellulose/collagen hydrogel beads have been prepared by a simple method. It was found that chitosan crosslinked cellulose/collagen/chitosan hydrogel beads (CCHB-CS) had better acid assistant in lower pH solutions even0.1mol/L HCl and higher mechanical strength than cellulose/collagen hydrogel beads (CCHB) without crosslinked agent chitosan, and cellulose/chitosan hydrogel beads (CCSHB). Moreover, the adsorption capacity for the hydrogel beads showed pH dependent. Furthermore, the adsorption isotherms of the hydrogel beads were better fitted for Langmuir equation than Freundlich equation. |
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