Selective adsorption of cationic dyes by layered double hydroxide with assist algae (Spirulina platensis) to enrich functional groups

The present study involved the preparation, characterization, and evaluation of layered double hydroxide (LDH) with the assistance of the algae Spirulina platensis (NiAl-Sp and ZnAl-Sp). These materials were investigated for their potential for selective adsorption of cationic dyes, including rhodamine B, malachite green, and methylene blue. The adsorbents exhibit a significant level of selectivity in their capacity to adsorb malachite green in comparison to other cationic dyes. The next parameter of adsorption was evaluated in malachite green as the selective adsorption of cationic dyes. Based on the Langmuir isotherm model, the calculated maximum adsorption capacities of NiAl-Sp and ZnAl-Sp for malachite green were determined to be 478.190 mg/g (pH = 4, 50 °C for 30 min) and 123.457 mg/g (pH = 4, 30 °C for 30 min), respectively. The main processes of adsorption encompassed not only electrostatic interactions but also hydrogen bonding and π-π interactions involving the dye and the amino, hydroxyl, and carboxyl functional groups derived from Spirulina platensis. Spirulina platensis enhances the functional group of LDH. The findings of this study indicate that the NiAl-Sp and ZnAl-Sp composite demonstrated stability as a sorbent for the adsorption of malachite green. Furthermore, it was observed that this composite could be utilized for up to four adsorption cycles, but there was a noticeable decrease in its adsorption capability over time. The findings revealed that the synthesized composite adsorbents of NiAl-Sp and ZnAl-Sp exhibit high efficacy in the adsorption of malachite green from effluent.