Effect of total aluminum concentration on the formation and transformation of nanosized Al13 and Al30 in hydrolytic polymeric aluminum aqueous solutions

Influence of total aluminum concentration （CAIT） on the generation and transformation of nanosized AI13 and AI30 in hydrolytic polyaluminum aqueous solutions was investigated using high field 27AI NMR and time-developed AI-Ferron complex colorimetry. When prepared at the optimal basicity （B） of Al13 generation and 80℃, the All3 species in polyaluminum solution tends to further polymerize and convert to AI30 and higher polymers when CAI; 〉0.2 mol· L^-1, but Al13 does not convert to AI30 quantificationally, as the formation of Alu from Al13 and AI30 is accelerated in the same way. The conversion rate of All3 is accelerated by the increase in CAIT. When CAlT 〉0.75 mol·.L^-1, Al13 content decreases rapidly, and AI30 content increases continuously and becomes the dominant nanometer polynuclear aluminum species. AIm is one of prerequisites of Al13 conversion to AI30. When CAI; increases and B reduces, the polymerization rate between Al13 and Aim increases, and at the same time, the dissociation reaction rate of All3 and AI30 by H^＋ also increases. The latter becomes the dominant reaction in polyaluminum solution with low B value, so AI30 decreases with the increasing CAlT. The hydrolytic polyaluminum solution with Al13 content beyond 80% can only be prepared under the condition of CAlT〈0.5 mol· L^-1 and optimal B value.

Effect of total aluminum concentration on the formation and transformation of nanosized Al13 and Al30 in hydrolytic polymeric aluminum aqueous solutions

Influence of total aluminum concentration (C_AlT) on the generation and transformation of nanosized Al₁₃ and Al₃₀ in hydrolytic polyaluminum aqueous solutions was investigated using high field ²⁷Al NMR and time-developed Al-Ferron complex colorimetry. When prepared at the optimal basicity (B) of Al₁₃ generation and 80℃, the Al₁₃ species in polyaluminum solution tends to further polymerize and convert to Al₃₀ and higher polymers when C_AlT >0.2 mol·L^&#8722;1, but Al₁₃ does not convert to Al₃₀ quantificationally, as the formation of Al_u from Al₁₃ and Al₃₀ is accelerated in the same way. The conversion rate of Al¹³ is accelerated by the increase in C_AlT. When C_AlT >0.75 mol·L^&#8722;1, Al₁₃ content decreases rapidly, and Al₃₀ content increases continuously and becomes the dominant nanometer polynuclear aluminum species. Al_m is one of prerequisites of Al₁₃ conversion to Al₃₀. When C_AlT increases and B reduces, the polymerization rate between Al₁₃ and Al_m increases, and at the same time, the dissociation reaction rate of Al₁₃ and Al₃₀ by H⁺ also increases. The latter becomes the dominant reaction in polyaluminum solution with low B value, so Al₃₀ decreases with the increasing C_AlT. The hydrolytic polyaluminum solution with Al₁₃ content beyond 80% can only be prepared under the condition of C_AlT<0.5 mol·L^&#8722;1 and optimal B value.