Coconut husk-raw clay-Fe composite: preparation, characteristics and mechanisms of Congo red adsorption

Abstract

The release of unspent dyes from industries constitutes hazard and environmental challenges. For rapid and efficient removal of Congo red from aqueous solutions, a composite was prepared from coconut husk, raw clay, Fe(II) and Fe(II) compounds. Adsorption variables (initial pH of the solution, contact time, temperature and initial concentration of Congo red) were varied to understand the characteristics and mechanisms of the adsorption process. The composite was characterised using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM)–Energy dispersive X-ray (EDX) spectroscopy, nitrogen adsorption–desorption isotherm, X-ray Diffraction (XRD) spectroscopy and pH of the point zero charge (pHpzc). The optimal values of the pH, equilibrium time and temperature for adsorption of Congo red by the composite are 2, 40 min and 50 °C, respectively. The kinetic and equilibrium data followed Avrami fractional order and Langmuir models, respectively. A 1.0 g of the composite could maximally take up 1649.3 mg of Congo red at 50 °C. The values of ΔG° are in the range of − 27.901 to − 24.492 kJ mol–1 while the value of ΔH° is − 72.239 kJ mol–1. Hence, the removal of the Congo red by the composite was spontaneous, feasible and exothermic. The adsorption process was biphasic and followed physisorption process. Electrostatic interaction played a significant role in the removal of Congo red by the composite. The combine data in this study have proven that the clay composite, a cheap adsorbent, can be used for remediation of water contaminated with Congo red.

Study adsorbents based on bent-Al13-CS-CTA and its application to the removal of CR from wastewater

“…At higher pH values, anionic dyes and OH − ions compete with each other for cationic adsorbents, resulting in a significant decrease in the removal rate. 37 This phenomenon may also be attributed to OH − ions destroying the structure of bent-Al 13 -CS-CTA. Within a pH range from 3 to 9, there is an improvement in removal rate from 70.54% to 90.16%.…”

Preparation of Breadfruit Leaf Biochar for the Application of Congo Red Dye Removal from Aqueous Solution and Optimization of Factors by RSM-BBD

“…If the intraparticle is the only rate-determining step, the graph between q t and t 1 / 2 must be linear. If not, intraparticle diffusion does not represent the sole mechanism determining rate [88–90]. Surface diffusion is represented by the first segment of the curve, whereas intraparticle diffusion is represented by the linear component [91, 92].…”

“…As previously stated, the removal of Congo by breadfruit leaf biochar supported the Langmuir equilibrium model. This isotherm is assumed to have resulted from the adsorption of adsorbate onto a microporous adsorbent (breadfruit leaf biochar), whose surface was coated in a monolayer of adsorbate (Congo red) [90]. Figure 1(b) depicts the FTIR spectrum of Congo red, and the peak at 3731 cm −1 reveals the presence of hydroxyl (OH) and NH 2 groups in the compound.…”

Zinc Recovery from Alkaline Batteries Using Cyanex 272 Impregnated on Polyurethane Foam

“…Figure 7(C) shows the intraparticle plot. There are two linear sections in the plot and this observation signi es two steps mechanism for the adsorption process [32,33]. The rst linear section is a fast process of adsorption and this process represent the transference of Zn ions from M olarity = 100×%purity×D molecularmass solution onto PUF [31,32].…”