Adsorption of phosphate at the aluminum (hydr)oxides–water interface: Role of the surface acid–base properties

Abstract

In this paper, the adsorption of phosphate on two crystallized aluminum oxides, pseudo-boehmite (pseudo-␥-AlOOH) and ␣-Al 2 O 3 , was studied. The adsorption experiments were carried out in 0.01 M KNO 3 solutions at pH 4 and 6, respectively. Adsorption densities were calculated to evaluate the phosphate adsorption affinity for the two aluminum oxides. To better understand the effect of surface properties on the adsorption behavior of phosphate, the surface structure and properties were investigated with X-ray diffraction, N 2 adsorption-desorption, electron microscope observation and surface acid-base titrations. The results from adsorption isotherms showed that at both pH 4 and 6, pseudo-␥-AlOOH exhibited greater adsorption capacity than ␣-Al 2 O 3 . For both pseudo-␥-AlOOH and ␣-Al 2 O 3 , the adsorbed amount of phosphate at pH 4 was higher than that at pH 6. Adsorption density calculation indicated that ␣-Al 2 O 3 had greater affinity for phosphate than pseudo-␥-AlOOH. Information gained from examinations of surface properties revealed that the specific surface area played an important role on adsorption capacity, while the acidity of surface aluminol groups evaluated from acid-base titration curves contributed more to adsorption affinity and consequently the adsorption density.

Defluoridation performance and mechanism of nano‐scale aluminum oxide hydroxide in aqueous solution

“…Figure 1 shows the XRD results of the sample. The main diffraction peaks can be indexed as boehmite AlOOH 22, 23. The very sharp peaks indicate high crystallinity of the synthesized product.…”

Enhancing phosphate adsorption by Mg/Al layered double hydroxide functionalized biochar with different Mg/Al ratios

“…It was found that, for three different Mg/Al-LDHs biochar composites, the equilibrium pH of each composite-related filtrate was higher than the initial pH from 3 to 9, and lower than the pH from 9 to 11. This can be attributed to the acid-base properties of hydroxyl groups on adsorbent surface, which resulted in the protonation or deprotonation of its structure (Lǚ et al, 2013;Yang et al, 2007). The positively protonated Mg/Al-LDHs surface was favored for phosphate adsorption.…”

Phosphate adsorption onto thermally dehydrated aluminate cement granules

“…making them harder to react with phosphate. 14,35 Hence, the phosphate adsorption on T600 was better under neutral and acidic conditions.…”