Phosphorus Binding by Lanthanum Modified Pyroaurite-like Clay: Performance and Mechanisms

Abstract

In situ immobilization of phosphorus (P) by using P binding agents is a facile and effective strategy for eutrophication control. Currently, the most successful commercial agent (Phoslock, a lanthanum modified bentonite, LMB) still suffers low P removal efficiency from natural waters of complex chemistry, largely due to the competitive complexation of the active La species by humic substances (HAs) and bicarbonate. Herein, we describe an attempt to address these issues by intercalating La into Mg/Fe layered double hydroxides, a pyroaurite-like anionic clay, to obtain a hybrid agent (denoted L-CMF-1.0) of phosphate capacity five times higher than that of LMB. More attractively, the binding stability and capacity of L-CMF-1.0 toward P were significantly enhanced in the presence of HAs and bicarbonate, resulting in a high La usage (P/La ratio at ∼1.30). A continuous P immobilization test in the simulated natural waters validates that the addition of L-CMF-1.0 at 0.12 g/L could result in an efficient P removal from 580 μg/L to <100 μg/L within 38 days, outperforming LMB within 10 days only under otherwise identical conditions. Such improvement results from the rational design of the agent structure, i.e., the host, not only contributes to the direct P uptake but also provides a flexible nanoshelter microenvironment to favor the specific La− P interaction under complex solution chemistry. This work is believed to shed new light on the rational design of P binding agent for enhanced eutrophication control.

Phosphorous recovery from water via batch adsorption enrichment combined with struvite crystallization in a fluidized bed reactor

“…However, we cannot simply attribute inner-sphere surface complexation to the main adsorption mechanism responsible for P uptake since conventional LDHs often show a higher preference for P over nitrate 44,50 . Nonetheless, although anion exchange is usually recognized as the principal adsorption mechanism of LDHs adsorbents 32, 47 , there is also much spectroscopic evidence suggesting that surface complexation at the edges of LDHs can also play a significant contribution to P adsorption 19,26,50 .…”

“…In general, P adsorption on LDHs is often subjected to competition from various co-occurring anions, e.g., nitrate, sulfate, chloride, and bicarbonate ions 15,25 . Interestingly, incorporation of a certain P-preferring element (e.g., La, Zr) into conventional LDHs can effectively enhance their P adsorption capacity and selectivity 11,23,[26][27] .…”

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.…”

Advancing Materials for Environmental Remediation and Human Health Protection

“…To address the limited adsorption capacity of commercial phosphate adsorbents (e.g., lanthanum-modified bentonite clay) used for eutrophication control of natural waters, Pan and co-workers designed, synthesized, and tested a La-containing Mg/Fe layered double hydroxide (LDH) in simulated and real waters. 6 The higher PO 4…”

“…The more open nanostructure presumably leads to greater accessibility of the Hg 0 species to reactively bind to the exposed sulfur sites to form HgS. To address the limited adsorption capacity of commercial phosphate adsorbents (e.g., lanthanum-modified bentonite clay) used for eutrophication control of natural waters, Pan and co-workers designed, synthesized, and tested a La-containing Mg/Fe layered double hydroxide (LDH) in simulated and real waters . The higher PO 4 3– capacity results from the positively charged LDH sheets and the intercalated lanthanum oxo species that bind to PO 4 3– electrostatically and covalently, respectively.…”