Halloysite Nanotubes as Adsorptive Material for Phosphate Removal from Aqueous Solution

Abstract

In this study, we were aiming at testing halloysite nanotubes as an efficient adsorbent for the removal of phosphate from agricultural runoff. Adsorption of phosphate onto powder and granular form of halloysite nanotubes has been examined by using the classical batch method and diffusion experiments at room temperature. Different forms of halloysite nanotubes were investigated to explore the effect of structure on the adsorption of phosphate. The maximum adsorption efficiency was obtained for powder halloysite nanotubes (79.5%) and granular form (94.7%). It is believed that the pore space of the granular halloysite nanotubes accommodates phosphorus in addition to physico-chemically bound phosphate at surfaces. The pseudo-first order and pseudo-second order model fitted well the experimental kinetic data for both powder and granular form of halloysite nanotubes. The fit of the Freundlich isotherm model was superior as compared with the Langmuir approach, implying that the halloysite nanotubes are heterogeneous because of multiple surface groups and different pore structures. The two forms of halloysite nanotube tested have the abundant potential for removal of phosphate from agriculture runoff. Additional investigations at the pilot scale are, however, required to draw definite conclusions.

Selective removal of nitrate using a novel asymmetric amine based strongly basic anion exchange resin

“…To understand the sorption mechanism in the nitrate sorption process, the experimental data were fitted with three common kinetic models, namely pseudo-first-order equation (equation (2)), pseudo-second-order equation (equation (3)) and intraparticle diffusion equation (equation (4)) (Fu et al., 2015; Saki et al., 2019) where Q e and Q t are the sorption amount (mg/g) at equilibrium and at time t (min), respectively; C (mg/g) is a constant; while k 1 (1/min), k 2 (g/mg/min) and k ipd (mg/g/min 0.5 ) are the rate constants for the pseudo-first-order, pseudo-second-order and intra-particle diffusion equations, respectively. The correlation parameters and coefficients ( R 2 ) are listed in Table 2.…”

“…The maximum amount of nitrate adsorbed onto SE-1 was found higher than that on A 520E when the sorption equilibrium reached. To understand the sorption mechanism in the nitrate sorption process, the experimental data were fitted with three common kinetic models, namely pseudo-first-order equation (equation 2), pseudo-second-order equation (equation 3) and intraparticle diffusion equation (equation 4) (Fu et al, 2015;Saki et al, 2019) Q t ¼ Q e ð1 À e Àk 1 t Þ…”

Adsorption of Nitrate by a Novel Polyacrylic Anion Exchange Resin from Water with Dissolved Organic Matters: Batch and Column Study

“…Finally, a larger h0 value of AEE-3 was obtained, and the difference in the adsorption rate is related to the difference of the resin matrix. Figure 3 describes the effect of contact time on NO 3 − -N uptake by AEE-3 and A520E at 298 K, and all the data were simulated using two commonly used kinetic models [21,22]:…”

“…describes the effect of contact time on NO3 − -N uptake by AEE-3 and A520E at 298 K, and all the data were simulated using two commonly used kinetic models[21,22]:Pseudo-first-order:…”

Adsorption of phosphate by halloysite (7 Å) nanotubes (HNTs)

“…Whilst kaolinite has been studied regularly for its phosphate adsorption properties (Edzwald et al , 1976; He et al , 1997; Gimsing & Borggaard, 2002; Kamiyango et al , 2009; Gérard, 2016), there is surprisingly little published work on halloysite (7 Å). Very recent work that has investigated halloysite has found adsorption capacities of 1.5 mg g –1 for phosphate after 3 h equilibrium time (Almasri et al , 2019), whilst Saki et al (2019) reported that granular halloysite adsorbs more phosphate than powdered halloysite due to the availability of pore space, with a maximum adsorption of ~1.2 mg g –1 phosphate.…”