Enhancement of Phosphate Adsorption on Zirconium Hydroxide by Ammonium Modification

Abstract

Surface modification of adsorbents plays a crucial role in its adsorption performance. Furthermore, the most important step in modification is to design the modification groups based on target pollutants. In this study, the phosphate adsorption performance of zirconium hydroxide was enhanced by different ammonium modification as a result of increasing utilization efficiency of adsorption site. The maximum capacity is 155.04 mg/g from the zirconium hydroxide modified by dimethylamine. In comparison with undecorated zirconium hydroxide, the selectivity factors for Cl − , SO 4 2− , and NO 3 − are all raised by almost 2 times by dimethylamine modification. The mass transfer rate K 2 also increase 6 times using N-methylaniline and N-ethylmethylamine. Results from zeta-potential and FT-IR revealed that the enhanced adsorption capacity for phosphate were directly related to the inner-sphere complex and electrostatic interactions (quaternary ammonium groups and phosphate) and ligand exchange (the hydroxyl groups of zirconium hydroxide and phosphate). Moreover, the utilization ratios of hydroxyl groups on adsorbents were improved from 22.9% to 33.9% by dimethylamine modification, which is proved by XPS. At last, the modified zirconium hydroxide presents excellent performances of anti-interference in real wastewater. Overall, modified zirconium hydroxide is considered to have great potential for engineering application, and then the method of increased utilization of the adsorption site gives a new route for other adsorption systems.

Amino‐functionalized magnetic zirconium alginate beads for phosphate removal and recovery from aqueous solutions

“…Obviously, the amino groups played an important role in enhancing phosphate adsorption. When the pH value was increased from 2.0 to 10.0, q t decreased to 18.11 mg‐P/g; this may have been due to the more negatively charged surface of the adsorbent and the competition between the phosphate and hydroxyl ions in the solution for capturing the binding sites of the adsorbent at high pH . Consequently, pH 2 was chosen for further adsorption experiments:…”

“…However, q t decreased from 39.02 to 33.25 mg‐P/g with increasing concentration of from 0 to 100 mmol/L. The adsorption process, driven by outer sphere association through electrostatic forces, was very sensitive to additive electrolytes, whereas the formation of the inner sphere complex always preferred to show little effect to common anion interference . The greater effect of on the adsorption performance may have been due to the facts that (1) could associate with binding sites on the adsorbent, such as Zr 4+ , to form strong complexes and (2) the accumulation of with a higher negative charge on the surface of the adsorbent may have strengthened the formation of negatively charged surface sites and, thus, decreased q t …”

“…When the pH value was increased from 2.0 to 10.0, q t decreased to 18.11 mg-P/g; this may have been due to the more negatively charged surface of the adsorbent and the competition between the phosphate and hydroxyl ions in the solution for capturing the binding sites of the adsorbent at high pH. 11 Consequently, pH 2 was chosen for further adsorption experiments: Figure 3(a) shows that when the adsorbent dosage was increased from 1.25 to 10.00 g/L, the removal efficiency increased from 56.90 to 99.77% (presumably because of the larger amount of available adsorption sites), whereas q t decreased from 48.78 to 10.89 mg-P/g (mainly because of the unsaturated binding sites throughout the adsorption process). Figure 3(b) shows that as the initial P concentration was increased from 10 to 150 mg/L, q t increased from 4.15 to 47.07 mg-P/g; this was attributed to the increase in the driving force provided by the concentration gradient of phosphate between the aqueous and solid phases.…”

“…The adsorption process, driven by outer sphere association through electrostatic forces, was very sensitive to additive electrolytes, whereas the formation of the inner sphere complex always preferred to show little effect to common anion interference. 11 The greater effect of SO 2− 4 on the adsorption performance may have been due to the facts that (1) SO 2− 4 could associate with binding sites on the adsorbent, such as Zr 4+ , to form strong complexes 25 and (2) the accumulation of SO 2− 4 with a higher negative charge on the surface of the adsorbent may have strengthened the formation of negatively charged surface sites and, thus, decreased q t . 25 Figure 3(d) shows that the change in q t was not obvious with increasing temperature from 25 to 65 C; this suggested that the temperature had little effect on phosphate adsorption.…”

“…The species of orthophosphate are strong ligands and oxides of transition metals, such as Zr(IV), Fe(III), and Cu(II), through the formation of inner sphere complexes, which have hard Lewis acid properties, via Lewis acid–base interactions . Because Zr(IV) exhibits a remarkable affinity toward phosphate, a variety of Zr(IV)‐based materials, including zirconium oxide, zirconia‐functionalized graphite oxide, and zirconium hydroxide by ammonium modification, have been explored for the removal of phosphate. However, these inorganic adsorbents are nonbiodegradable, difficult to separate from aqueous solutions, and not easy to use in practice for continuous column adsorption of phosphate because these powder adsorbents may result in the frequent blocking of the column.…”