Removal of cationic and anionic dyes using Ca-alginate and Zn-Al layered double hydroxide/metal-organic framework

In this study, a novel effective bio adsorbent was produced and employed to remove congo red and methylene blue dyes from water matrices. First, Zn-Al layered double hydroxide (Zn-Al LDH) was manufactured in a hy-drothermal process. Next, through in-situ nucleation and growing of crystalline NH2-modified Ti metal-organic framework (NH2-MIL-125(Ti) on Zn-Al sheets by solvothermal method, Zn-Al LDH@NH2-MIL-125(Ti) hybrid was produced. The prepared hybrid showed good adsorption capacity (qmax values: 294 mg/g and 158 mg/g) for congo red and methylene blue dyes in optimum condition (adsorbent amount = 5-7 mg, dye concentration = 100-150 mg/L, V = 10 mL, pH = no adjustment, and contact time = 2-5 h). Based on the isotherm and kinetic models, the Langmuir isotherm, as well as the pseudo-second-order model, were fit to the equilibrium data. In the next attempt, to improve the reusability of the powder and particle form of Zn-Al LDH@NH2-MIL-125(Ti) hybrid, as well as prevent of formation of secondary contamination in water, Na-alginate, as a cheap and effective substrate, was used. Novel architectures of robust, reusable, and efficient Ca-alginate/Zn-Al LDH@NH2- MIL-125(Ti) microgel beads were prepared and the performances of the microbeads were compared with pure LDH@NH2-MIL-125(Ti) hybrid.

Automated summary

A novel effective bio adsorbent, Zn-Al LDH@NH2-MIL-125(Ti) hybrid, was produced and used to remove congo red and methylene blue dyes from water matrices. The hybrid showed good adsorption capacity and efforts were made to improve reusability and prevent secondary contamination.