Mg–Al-Layered Double Hydroxide (LDH) Modified Diatoms for Highly Efficient Removal of Congo Red from Aqueous Solution

Abstract

In this work, diatomaceous earth (DE) or diatoms are modified with Mg–Al-layered double hydroxide (DE-LDH) using the facile co-precipitation method to demonstrate their application for the removal of toxic dyes such as Congo Red (CR), which was used as a model. Field emission scanning electron microscopy (FE-SEM) characterization confirms the successful modification of diatom microcapsules structures, showing their surface decorated with LDH nano patches with sheet-like morphologies. The surface area of the DE was enhanced from 28 to 51 m2/g after modification with LDH. The adsorption studies showed that the maximum CR removal efficiency of DE and DE-LDH was ~15% and ~98%, respectively at pH 7, which is a significant improvement compared with unmodified DE. The maximum adsorption capacities of DE-LDH were improved ten times (305.8 mg/g) compared with the bare DE (23.2 mg/g), showing very high adsorption performances. The recyclability study of DE-LDH up to five cycles, after desorbing CR either by methanol or by NaOH, showed the efficient removal of the CR by up to three cycles via adsorption. The presented study suggests the promising application of DE-LDH as an effective material for application in the removal of CR from aqueous solutions for industrial wastewater treatment.

Itaconic acid-modified layered double hydroxide as a ‎novel adsorbent for effective removal of Congo red from aqueous solutions

“…To study the effect of sample solution pH on the adsorption of Congo red onto the Cu-Ca-Al-LDH and LDH-ITA adsorbents, sample solution pHs between 5.0 and 9.0 were investigated. This range was selected due to the instability of Congo red below pH 5 [28]. All the experiments were done using 5 mL of an aqueous sample solution containing 50 mg L -1 of Congo red with the adsorbent dosage of 10.0 mg.…”

“…The decrease in the Congo red removal efficiency is may be due to that the surface of the adsorbents becomes highly negative when pH increased from 5.0 to 9.0. The negative charge on the surface of the adsorbents results in electrostatically repelling of negatively charged Congo red [28]. Accordingly, pH=5.0 was selected for further experiments.…”

“…These relatively complex organic molecules are widely used in different industries such as leather tanning, food processing, paper making, cosmetics, textile, and plastics. As a water-soluble member of synthetic dyes, Congo red is used in a huge quantity in textile and biochemistry based industries [28]. It is a benzidine-based anionic dye that was discovered by Paul Bottinger in 1883.…”

Layered Double Hydroxides in Bioinspired Nanotechnology

“…Interesting examples have also been provided for the removal of Congo red (CR), a dye which is widely employed in many textiles and biotechnological based industries. MgAl-LDH modified diatoms [172] and bioinspired magnetic ZnFe 2 O 4 microspheres synthetized using pine pollen and covered with MgAl-LDH [173] have been used with this purpose. The presence of LDH significantly improved the absorption capacity of the composite material toward the dye, reaching values of about 300 mg/g in both cases.…”

Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide

“…Their chemical structures have many complex and durable aromatics which are shown in Figure 1. Therefore, several methods have been applied to treat the dyes from wastewater such as adsorption, ion exchange, Fenton oxidation, photocatalytic degradation, and advanced oxidation processes [8][9][10][11][12][13][14]. Although these methods are effective, they still have some disadvantages.…”