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The flocculation effects of homemade hydroxamated flocculant(HPAA)and commercially available sodium polyacrylate(PAAS)on synthetic goethite suspensions with different solid contents were studied.The adsorption mechanism of HPAA or PAAS on the surfaces of goethite was investigated.The settling rate of 50 g/L goethite suspension with HPAA(1.74 m/h)was faster than that with PAAS(0.54 m/h),which indicated that HPAA exhibits better flocculation performance than PAAS does.It could be found that the stretching vibration of carbonyl band in hydroxamic acid groups of HPAA was downshifted from 1 654 cm~(-1) to 1 645 cm~(-1) and a new adsorption band appeared at 1 455 cm-1,which demonstrated that a five-membered ring chelate may be formed among iron atoms of goethite surfaces,the hydroxyl groups and the carbonyl groups in hydroxamic acid groups of HPAA.In the case of PAAS,the separation of the asymmetric and symmetric stretches of the carboxylate groups in adsorbed PAAS was 163 cm-1,which was greater than that of unadsorbed PAAS with 157 cm~(-1).There was no indication of a contribution from the monodentate adsorption between iron atoms of goethite surfaces and carboxylate groups of PAAS,but there may exist a bi-dentate bridging structure.Compared with synthetic goethite,XPS curve fittings of Fe 2p spectra showed that the binding energies of the main Fe 2p3/2 and Fe 2p1/2 resolved peaks on HPAA-treated goethite surfaces were correspondingly decreased by 0.9 and 0.7 e V,while those on PAAS-treated goethite surfaces were correspondingly decreased by 0.7 and 0.3 e V.The characteristic N 1s peak of HPAA and C 1s peak of PAAS were correspondingly detected on HPAA-treated and PAAS-treated goethites,and a binding energy change of N 1s spectrum of adsorbed HPAA was observed.The relative atomic ratios of C/Fe,N/Fe and O/Fe on HPAA-treated and PAAS-treated goethite surfaces were increased.All the results suggested that HPAA or PAAS was adsorbed on the goethite surfaces by the chemisorption,and a stronger adsorption of HPAA on the goethite surfaces happened than that of PAAS.
The flocculation effects of homemade hydroxamated flocculant (HPAA) and commercially available sodium polyacrylate (PAAS) on synthetic goethite suspensions with different solid contents were studied. The adsorption mechanism of HPAA or PAAS on the surfaces of goethite was investigated. The settling rate of 50 g / L goethite suspension with HPAA (1.74 m / h) was faster than that with PAAS (0.54 m / h), which indicates that HPAA exhibits better flocculation performance than PAAS does. It could be found that the stretching vibration of carbonyl band in hydroxamic acid groups of HPAA was downshifted from 1 654 cm -1 to 1 645 cm -1 and a new adsorption band appeared at 1 455 cm -1, which demonstrates that a five-membered ring chelate may be formed among the iron atoms of goethite surfaces, the hydroxyl groups and the carbonyl groups in hydroxamic acid groups of HPAA. in the case of PAAS, the separation of the asymmetric and symmetric stretches of the carboxylate groups in adsorbed PAAS was 163 cm-1, which was gre ater than that of unadsorbed PAAS with 157 cm -1. There was no indication of a contribution from the monodentate adsorption between iron atoms of goethite surfaces and carboxylate groups of PAAS, but there may exist a bi-dentate bridging structure. Compared with synthetic goethite, XPS curve fittings of Fe 2p spectra showed that the binding energies of the main Fe 2p3 / 2 and Fe 2p1 / 2 resolved peaks on HPAA-treated goethite surfaces were correspondingly decreased by 0.9 and 0.7 e V, while those on PAAS -treated goethite surfaces were correspondingly decreased by 0.7 and 0.3 e V. The characteristic N 1s peak of HPAA and C 1s peak of PAAS were correspondingly detected on HPAA-treated and PAAS-treated goethites, and a binding energy change of N 1s spectrum of adsorbed HPAA was observed. The relative atomic ratios of C / Fe, N / Fe and O / Fe on HPAA-treated and PAAS-treated goethite surfaces were increased. All the results suggested that HPAA or PAAS was adsorbed on the goethite surfaces by the chemisorption, and a strengthening adsorption of HPAA on the goethite surfaces happened than that of PAAS.