Layered double hydroxide ion exchangers on superparamagnetic microparticles for recovery of phosphate from waste water

Abstract

Superparamagnetic microparticles modified with an ion exchange system are reported for the recovery of phosphate from waste water by a magnetic separation technique. Layered double hydroxides (LDH), anionic clays, are precipitated from an aqueous solution and deposited by an ultrasonic treatment on superparamagnetic microparticles consisting of Fe3O4 multicores embedded in a SiO2 matrix. Deposition can be conducted in a batch process as well as in a continuous way, using an ultrasonic flow cell. The obtained composite particles show good magnetic separability and have a specific surface area of around 100 m(2) g(-1). Zr doped LDH shows improved phosphate adsorption in waste water. After magnetic separation and regeneration, the composite particles are re-used which is demonstrated for four cycles. Phosphate ions are concentrated in the regeneration solution. Simple, low cost, and a fast continuous synthesis of the composite particles paves the way for application beyond lab scale in real waste water treatment plants

Facile upscaled synthesis of layered iron oxide nanosheets and their application in phosphate removal

“…As a class of anionic clays, layered double hydroxides (LDHs) comprise positively charged trioctahedral metal hydroxide layers and interlayer anions with the general formula of LDHs are considered as efficient adsorbents to remove phosphate with adsorption capacities ranging from 16 to 47 mg P per g. 3,[11][12][13] Studies show that the adsorption capacity of LDHs is notably determined by the composition and properties of the metal hydroxide layers. 11,14 For example, the increase of trivalent Al ions or the addition of tetravalent Zr into the metal hydroxide layers can signicantly enhance phosphate removal, 1,15 whereas, this can increase the release of toxic elements such as Al into the aquatic environment.…”

“…For example, a previous study showed that NO 3 À type Zn/Al LDH exhibits much stronger adsorption for phosphate than CO 3…”

“…Various physicochemical approaches have been developed to recover phosphate from wastewater, such as precipitation, crystallization, anion exchange, and sorption. [1][2][3][4][5][6] Typically, in virtue of advanced nanotechnology, a number of nanomaterials with unique structures have been developed exhibiting excellent efficiency for removing phosphate.…”

Fabrication of free-standing bio-template mesoporous hybrid film for high and selective phosphate removal

“…Al, Fe, etc.) doped or modified materials for increase the selectivity of phosphate adsorption has become an increasing area of research, attributed to the specific adsorption mechanism between metal active sites and phosphate [2,[16][17][18]. Among them, lanthanum (La)-doped mesoporous silicon materials attract a great amount of attention as promising phosphate sorbents considering the advantages such as a superior adsorption capacity (more than 20 mg g À1 ), high selectivity, and high removal rate especially [19,20].…”

A green route to synthesize layered double hydroxides

“…Layered double hydroxides (LDHs), also called hydrotalcite‐like compounds or anionic clays, consist of positively charged metal hydroxide sheets, interlayer anions and water. They can be represented by a general formula, , where M 2+ and M 3+ stand for divalent and trivalent metal cations respectively, and A n ‐ is the interlayer anions; y is the amount of interlayer H 2 O. Owing to their adjustable composition and structure, LDHs have many unique chemical properties and are used as fire‐retardants , catalysts , adsorbents , electrochemical materials , and others .…”