The ability of chitosan as an adsorbent for Cu (II) and Cr (VI) ions in aqueous solution was studied. The experiments were done as batch processes. Equilibrium studies were done on both cross-linked and non-cross-linked chitosan for both metals. Cr (VI) adsorption behaviour could be described using the Langmuir isotherm over the whole concentration range of 10 to 1000 mg·l -1 Cr. The maximum adsorption capacity for both types of chitosan was found to be 78 mg·g -1 for the non-cross-linked chitosan and 50 mg·g -1 for the cross-linked chitosan for the Cr (VI) removal. For the Cu (II) removal the Freundlich isotherm described the experimental data over the whole concentration range of 10 to 1000 mg·l -1 Cu (II). The maximum adsorption capacity for both types of chitosan can be estimated to be greater than 80 mg·g -1 . Cr (VI) removal was the highest at pH 5 but pH did not have a large influence on Cu (II). From these results it is clear that the adsorption of heavy metals is possible with chitosan, but that with this method, end concentrations of below 1 mg·l -1 can hardly be obtained.

Three commercial membranes (NF70, NF90 and TFC-SR) were firstly characterized in terms of pure water flux and the: rejection of uncharged (alcohols and sugars) compounds. Subsequently, the rejection of monovalent (sodium and chloride) and divalent (calcium and sulphate) ions in single (NaC1, CaC12 and Na2SO4) and binary (NaC1/Na2SO4, CaClJCaSO4, NaC1/CaC12 and Na2SO4/CaSO4) salt mixtures was studied. According to the pure water permeability the TFC-SR membrane is a loosely packed NF membrane (12.3 L.m-2.h-1.bar-1 ), while both NF70 and NF90 are tightly packed (2.6 and 3.6 L.m-2.h" 1.bar-I). According to the uncharged solute rejection, the MWCO~70 = 60, MWCO~9o = 200 and MWCOrFc.sR > 500. NF70 and NF90 were equally efficient in rejecting 1-2, 1-1 and 2-1 salts (>90%), while TFC-SR showed typical negatively charged surface behaviour, i.e., R (1-2) salt > R (1-1) salt > R (2-1). Sulphate rejectkm decreased in the presence of sodium chloride more significantly than in the presence of calcium chloride due to the more efficient retention of the bivalent calcium.

No abstract

No abstract

Ionic cross-linking between the SAC component and (a) F6PBI by imidazole group protonation or (b) N-methylmorpholine after quaternization.

No abstract

No abstract

No abstract