Simultaneous Removal of Phosphate and Nitrate on Calcined Mg-Al Layered Double Hydroxides

Abstract

The competitive adsorption of phosphate and nitrate from aqueous solution on calcined Mg-Al layered double hydroxides (Mg-Al CLDHs) were investigated. Experiments were carried out as a function of adsorbent dosage, contact time, initial pH and temperature. The adsorption processes of phosphate and nitrate were followed by the pseudo second-order and pseudo first-order kinetics, respectively. The X-ray diffraction patterns (XRD) showed structural reconstruction during sorption, the unchanged d-spacing d 003 indicated phosphate and nitrate were mainly adsorbed on the surface and the near-edge interlayer. The results of Fourier transformed infrared spectroscopy (FTIR) verified nitrate and phosphate adsorbed onto the CLDHs. Desorption behaviors indicated that nitrate can be more easily desorbed from loaded CLDHs than phosphate. The possible mechanism of phosphate adsorption was controlled by chemisorption, while nitrate adsorption was governed by physisorption. The results showed that the Mg-Al CLDHs can be used to simultaneously remove phosphate and nitrate from aqueous solution.

Comparative Adsorptive Removal of Phosphate and Nitrate from Wastewater Using Biochar-MgAl LDH Nanocomposites: Coexisting Anions Effect and Mechanistic Studies

“…The ∆S values specify the increase in the randomness of the solid/liquid interface during the adsorption process, exhibiting that the uptake of phosphate and nitrate onto B 5 MgAl composite were favorable processes. These thermodynamic modeling results are in good agreement with the findings of previously reported studies using various other MgAl LDHs for phosphate and nitrate adsorption [41,45,46]. FTIR, XRD, and SEM analyses were performed for B 5 MgAl composite after anions adsorption to provide further insight into possible adsorption mechanisms.…”

“…3− > OH − > NO 3 − according to the Hofmeister series [46], which could explain the decrease in nitrate adsorption at high pH values. The XRD patterns of B 5 MgAl composites before and after anions adsorption are given in Figure 7c.…”

“…Yao, et al [52] reported the formation of new Mg-P crystals in the forms of MgHPO 4 and Mg(H 2 PO 4 ) 2 (around 30 • (2θ)) after phosphate adsorption by Mg-biochar-LDH nanocomposite. Liao, Liu, Li and Yang [46] showed that Mg atoms played a more prominent role in phosphate and nitrate adsorption compared to Al atoms. As a consequence of XRD data assessment, the variations in layer charge density, phosphate intercalation into the interlayer, and formation of inner-sphere complexation contributed to the selectivity and phosphate adsorption capacity of the B 5 MgAl composite.…”

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides

“…At pH 4, the removal efficiency slightly decreased to 50.21%, and the adsorption capacity decreased to 26.20 mg/g. This observation can be attributed to the partial destruction of the CLDH structure (Liao et al 2020). For example, Tyner et al (2004) have proved that the sharp increase of Mg 2þ in solution is due to the complete dissolution of LDH in the pH 5 environment.…”

Facile Synthesis of Nanosized Magnesium-Aluminium Layered Double Hydroxides

“…references [3,11,13,[15][16][17][18][19][20][21][24][25][26][27][28][29][30][31][32][33] To name the most important applications of the LDH, their delaminated nano-sheets are promising materials for sensing [13,18,29,[31][32][33] and catalytic purposes [19], wastewater treatment (such as removal of As(V) and Cr(VI), phosphates and nitrates) [15,16,21,26], as fire-retardant [12,24,25,30], corrosion inhibitors supercapacitors, as biomaterials, drug delivery hosts, etc. [7,27,30].…”