Mg–Fe layered double hydroxide assembled on biochar derived from rice husk ash: facile synthesis and application in efficient removal of heavy metals

Abstract

The pollution of toxic and persistent heavy metals commonly exist in water environment; such multi-component pollutants pose a serious threat to human beings and other organisms. Herein, to make full use of the advantages of both layered double hydroxide (LDH) and rice husk ash (RHA), a novel Mg-Fe-LDH-RHA functional material was synthesized by assembling LDH on the biochar derived from RHA and used as an adsorbent for removal of heavy metal ions including Pb, Cu, Co, Ni, Zn, and Cd. The adsorption kinetics and isotherms of heavy metal ions in a mono-component system, the adsorption capacities in mixed multi-metal ion system, and the regeneration of the adsorbent were studied in detail. The results showed that the synthesized Mg-Fe-LDH-RHA might efficiently remove the above six heavy metals in water under optimized experimental conditions. Interestingly, the removal performance toward Pb(II) showed high static distribution coefficients (K) of ~ 10 mL/g and maximum capacity of ~ 682 mg/g. Besides, further characterizations of the adsorbent have been conducted, and the result suggested the formation of abundant functional groups including hydroxyl, carbonyl, and carboxyl groups. The removal mechanism of the metal ions might be related to ion-exchange, surface precipitation, complexation, and hydrogen binding during the interactions between the LDH-RHA material and pollutants. Such a facile and environmentally friendly approach, efficient removal performance suggests that the LDH-RHA material thus has potential for efficient removal of heavy metals in practical application.

Functionalized layered double hydroxide applied to heavy metal ions absorption: A review

“…Absorption sites have also increased. Silica aerogel, N-doped carbon nanosheet, graphene, biochar, and other materials that can provide many absorption sites and stable attachment sites can be used as substrates [90][91][92][93][94][95]. Because carbon-based materials contain more functional groups and larger specific surface areas, they have been extensively studied [96][97][98].…”

Comparative Study of Biochar Modified with Different Functional Groups for Efficient Removal of Pb(II) and Ni(II)

“…For instance, the preparation of graphene requires concentrated H2SO4 and HNO3 for exfoliation. Recent studies have shown that biochars obtained from waste biomass, such as rice husk (Yu et al, 2018) and peanut shells (An et al, 2019), have great potential as cost-effective adsorbents for Ni and Pb remediation in soil and water. Biochar has a high capacity for adsorbing heavy metals because of its porous structure and inhomogeneous surface chemistry (Martin et al, 2012).…”

Electrospun Polystyrene/LDH Fibrous Membranes for the Removal of Cd2+ Ions

“…This application has been attributed to the diversity and functionality of the interlayer region, in the LDH structure, that contains easily exchangeable intercalated anions and solvation molecules with hydrogen bonds. Moreover, the ability of LDH to remove soluble heavy metal ions was also explored [45]. However, regeneration of LDH and their agglomeration in solution restrict their application in water treatment [46], unless compounded with other materials in the form of functional composites that will minimize these shortcomings [47].…”