Raman spectroscopy of hydrotalcites with phosphate in the interlayer: implications for the removal of phosphate from water

Abstract

Hydrotalcites with phosphate in the interlayer were prepared at different pH values. At pH >11.0 (PO 4 ) 3− was the intercalated ionic species, whereas at pH < 11.0 a mixture of (PO 4 ) 3− and (HPO 4 ) 2− ions was intercalated. Powder X-ray diffraction shows that the hydrotalcite formed at pH 9.5 is poorly diffracting with a d-spacing of 11.9Å; whereas the d(003) spacing for the phosphate interlayered hydrotalcite formed at pH 11.9 and 12.5 was 8.0 and 7.9Å respectively. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. Raman spectroscopy of the phosphate interlayered hydrotalcites shows that the interlayered anion is pH dependent and only above pH 11.9 is the orthophosphate anion intercalated. At lower pH, the monohydrogen phosphate anion is intercalated. Raman spectroscopy shows that upon addition of the thermally activated hydrotalcite to an aqueous phosphate solution, results in the uptake of phosphate anion from the solution.

Thermal analysis of smithsonite and hydrozincite

“…Raman spectroscopy has proven very useful for the study of minerals [11][12][13]. Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as carbonates and hydroxycarbonate [14][15][16][17][18].…”

“…Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as carbonates and hydroxycarbonate [14][15][16][17][18]. Some previous studies have been undertaken by the authors using Raman spectroscopy to study complex secondary minerals formed by crystallisation from concentrated sulphate solutions [12][13][14][15][16][17][18][19][20][21]. Further hot stage Raman spectroscopy is most useful for the study of the thermal decomposition of minerals [22][23][24][25][26][27].…”

Natural halotrichites—an EDX and Raman spectroscopic study

“…Raman spectroscopy has proven very useful for the study of minerals [14][15][16] . Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as sulphates, alums and halotrichites [17][18][19][20][21] .…”

“…Indeed Raman spectroscopy has proven most useful for the study of diagenetically related minerals such as sulphates, alums and halotrichites [17][18][19][20][21] . Some previous studies have been undertaken by the authors using Raman spectroscopy to study complex secondary minerals formed by crystallisation from concentrated sulphate solutions [15][16][17][18][19][20][21][22][23][24] . In this work we extend this research by using Raman spectroscopy to study four natural halotrichites and compare the spectra with that of the natural minerals.…”

Raman spectroscopic study of the uranyl carbonate mineral voglite

“…[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Raman spectroscopy has proven most useful for the study of diagentically related minerals as often occurs with carbonate minerals. [30][31][32][34][35][36][37] No detailed Raman spectroscopic studies of the uranyl mineral voglite has been forth coming.…”