High Efficiency Phosphate Removal Was Achieved by Lanthanum-Modified Mesoporous Silica Aerogels with Cellulose-Guided Templates

Abstract

Removing excess phosphate from environmental water is extremely important to reduce eutrophication. In this study, cellulose nanocrystals (CNCs) were utilized as biological templates, and the SA-La-X was synthesized by calcination with lanthanum modification. Some characterization techniques were used to confirm the impregnation of La on the surface of mesoporous silica aerogel (SA). The obtained aerogels SA-La-5, 10, and 25 had large specific surface areas (262.69, 251.23, and 197.18 m2 g–1), and average pore sizes of aerogels SA-La-5, 10, and 25 were 5.14, 4.85, and 4.71 nm, respectively. The results manifested that sample SA-La-5 with the molar ratio of Si/La of 5:1 presented the maximum adsorption capacity of 42.08 mg g–1. Meanwhile, SA-La-X exhibited less La leaching, good stability, and strong selectivity for phosphate. Through the adsorption isotherm, the phosphate adsorption over SA-La-X samples followed the Langmuir model, and the kinetic experiment demonstrated that the adsorption process fitted the pseudo-second-order models. The phosphate adsorption mechanism of SA-La-X was detected by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), and it was found that the binding mechanism of the adsorbent and phosphorus included electrostatic adsorption, surface precipitation, and ligand exchange. Among them, electrostatic and ligand exchange were considered to be the main ways to selectively adsorb phosphate at pH 3.0. At the same time, the prepared SA-La-X with a cylindrical shape was easy to separate without causing secondary pollution to the water system, which would be the promising adsorbent for phosphate adsorption in the water environment to reduce eutrophication.

Revisiting the Temkin Isotherm: Dimensional Inconsistency and Approximate Forms

“…Fitting the Temkin-I equation to the entire range of an experimental isotherm profile can lead to a physically implausible situation. To expand on this point, the Temkin-I equation was fit to an equilibrium data set taken from the work of Yang et al, 42 who investigated the uptake of phosphate by an aerogel adsorbent. Figure 1A plots the moderately favorable data profile, which exhibits a gradual approach to an adsorption maximum.…”

Efficient removal of phosphate through adsorption by acidified diatomite loaded with La2O2CO3

“…13 A lanthanum-based modified calcium lignosulfonate prepared by Zhang et al 14 showed high loading of lanthanum, large surface area, and a maximum phosphate adsorption capacity of 107 mg g À1 . In addition, pyroaurite-like clay 15 and mesoporous silica aerogels with cellulose-guided templates 16 modified by lanthanum also exhibited good phosphate adsorption performance. Moreover, lanthanum hydroxide and lanthanum oxalate were also used to increase phosphate adsorption capacity, and they achieved better performance.…”

Effective and selective adsorption of La3+ by a poly-N-isopropylacrylamide phosphoric modified cellulose aerogel

“…In recent years, with the continuous development and use of lanthanum, it has become widely used in traditional industrial fields such as metallurgy, petrochemicals, glass ceramics, environmental protection, agriculture, and modern functional materials 4 such as permanent magnet materials, hydrogen storage materials, and luminescent materials. 5,6 Therefore, the rare earth metal lanthanum plays an irreplaceable role in practical applications, it has immeasurable prospects in future development and its value will become greater and greater with continuous development. 7,8 The current low-carbon technology has led to a surge in power-related equipment, and the use of permanent magnet materials developed by lanthanum has greatly increased, resulting in an insufficient supply of lanthanum in the development and supply market.…”