Highly selective and efficient removal and extraction of heavy metals by layered double hydroxides intercalated with the diphenylamine-4-sulfonate: A comparative study

Abstract

Six new NiCr layered double hydroxides (LDHs) intercalated with different inter-layeranions, including diphenylamine-4-sulfonate (DPA), dodecyl sulfonate (DS), pentansulfonate (PS), terephthalate (TA), fumarate (FA) and 2-ethylhexyl hydrogenphosphate (EHP), were synthesized and used to removal of Cd 2+ , Pb 2+ , Cu 2+ , and Zn 2+ ions from water samples. The maximum adsorption capacities (q m ) for the mentioned LDHs based on their inter-layer anions were DPA>DS>PS>TA>FA>DEHP. This observation highlights the key role of the structure of the inter-layer anions in the adsorption behavior of LDHs. The sulfonate-based LDHs showed better adsorption efficiency than carboxylate-based LDHs, and phosphonatebased LDHs showed the lowest adsorption efficiency. Also, at both high and low concentrations of the metal ions, the length of R-groups and the type of functional groups of inter-layer anions play a key role in the adsorption process. Subsequently, DPA-LDH, due to having the highest q m value among intercalated-LDHs, was chosen as an efficient sorbent for the removal of the metal ions from aqueous samples and its selectivity for adsorption of metal ions was investigated. DPA-LDH displayed a selectivity order of Zn 2+ <Cu 2+ <<< Cd 2+ < Pb 2+ for their adsorption, providing good separation of much more toxic metal ions of Cd 2+ and Pb 2+ from Zn 2+ and Cu 2+ . For the highly toxic Pb 2+ and Cd 2+ , enormous q m values as large as 479 and 282 mg g -1 can be obtained, respectively; and these are among the highest q m values reported for Pb 2+ and Cd 2+ sorbents. The very high distribution coefficient (K d ) values for Pb 2+ (1.99× 10 8 mL g -1 ) and Cd 2+ (1.99× 10 7 mL g -1 ), obtained using a V/m ratio of 2000 mLg -1 , place the DPA-LDH at the top of materials known for such removal.

Functionalized layered double hydroxides for innovative applications

“…247 Therefore, the removal of heavy metals from environmental medium such as water remains a key subject of research. Previous studies suggested that functionalized LDHs exhibit very favorable adsorption to heavy metals as measured by high adsorption capacity and selectivity, 2,66,76,247,[250][251][252] which resulted in effective removal of toxic metals to meet increasingly strict environmental regulations. For example, Ma and coworkers found that the intercalation of MoS4 2into MgAl-LDH interlayer space could not only endow MgAl-LDH with the ability to adsorb various heavy metal ions (Co 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Pb 2+ , Cu 2+ , Hg 2+ , and Ag + ) rapidly and effectively, but also offer high selectivity for some of these heavy metals.…”

A new magnetic bio-sorbent for arsenate removal from the contaminated water: Characterization, isotherms, and kinetics

“…Asiabi et al prepared different LDH s modified with the diphenylamine-4-sulfonate for the highly selective removal of the heavy metals. Also, they synthesized an Ni/Al LDH intercalated with zwitterionic glycine for the removal of As, Cr, and Se (27). Hu and O'Hare recommended the synthesis of belt-like Mg-Al LDHs modified using tri-block copolymers (28).…”

Synthesis of MgFe Layered Double Hydroxide from Iron-Containing Acidic Residual Solution and Its Adsorption Performance

“…mH 2 O] x− , where M II is a divalent cation, M III is a trivalent cation, and A n− is an anion. Their lamellar structure is based on brucite-like sheets, where some divalent cations are replaced with trivalent cations, resulting in some positively charged layers that contain between them various anions such as CO 3 2− , Cl − , NO 3 − , or even organic anions [4,5]. This structure increases their adsorptive properties, especially if the contaminant is in the form of oxyanions [6][7][8].…”