Electrospray Ionization Time-of-Flight Mass Spectrum Analysis Method of Polyaluminum Chloride Flocculants

Abstract

Electrospray mass spectrometry has been reported as a novel technique for Al species identification, but to date, the working mechanism is not clear and no unanimous method exists for spectrum analysis of traditional Al salt flocculants, let alone for analysis of polyaluminum chloride (PAC) flocculants. Therefore, this paper introduces a novel theoretical calculation method to identify Al species from a mass spectrum, based on deducing changes in m/z (mass-to-charge ratio) and molecular formulas of oligomers in five typical PAC flocculants. The use of reference chemical species was specially proposed in the method to guarantee the uniqueness of the assigned species. The charge and mass reduction of the Al cluster was found to proceed by hydrolysis, gasification, and change of hydroxyl on the oxy bridge. The novel method was validated both qualitatively and quantitatively by comparing the results to those obtained with the (27)Al NMR spectrometry.

Speciation, stability, and coagulation mechanisms of hydroxyl aluminum clusters formed by PACl and alum: A critical review

“…Feng et al had improved the method for identification of Al species in ESI-MS spectrum [25,26]. The general formula for identification of Al species form was…”

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

“…Chen et al reported that Al 13 showed high positive charge, stable structure, and strong binding affinity, and is the most active Al species in Al salts responsible for coagulation process [25]. In addition, Al 13 also contributed most to the amount of Al species for PACl in basicity range from 1.5 to 2.5 [26,27]. Our previous study indicated that pH significantly affected the Al species distribution of AlCl 3 and preformed PACl, and in acidic or alkaline pH region the ratios of monomeric Al increased whereas polymeric and colloidal Al species decreased as compared to the near-neutral pH region [21].…”

“…In this case fluoride removal was mainly attributed to physical adsorption and ion exchange effects [4,31], and the weakly acidic and acidic pH favored its removal. In B ranges from 1.0 to 1.5, PACl includes different Al species such as Al 2 , Al 4 , Al 7 and Al 13 et al [27], the ratios of monomeric Al species were observed to increase with lowered B. In this case coagulation dominated in the removal of fluoride, and different mechanisms such as complexed precipitation, charge attraction, and ion exchanges involve in and facilitated fluoride removal accordingly [32,33].…”

Roles of coagulant species and mechanisms on floc characteristics and filterability

“…The percent concentration of each species was determined by the ratio of the peak intensity for each species to the total intensity of all of the species (Feng et al, 2015. The samples were injected into the spectrometer at a flow rate of 10 L min In this study, ultra pure water was used as the black sample, and the mass spectra of black sample is shown in S- Fig.…”

“…Recently, ESI-TOF-MS has been applied in metal ions species identification for determination of molecular mass (Feng et al, 2015;Feng et al, 2011;Bi et al, 2012). In this study, two coagulants at the same concentration of 0.2 mM were used to detect the Al species distributions.…”