Eco-engineered natural clay: methylene blue adsorption optimized by RSM-ANN

Removal of a cationic dye from aqueous solution by natural clay

Comparative study on adsorption of cationic dyes and phenol by natural clays

Thisstudy aims to synthesize and analyzethe characteristics of natural clay as an adsorbent for cationic methylene blue, which can be easily manufactured as a low-cost natural clay powder. Natural clay was prepared and subsequently analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). The adsorption of methylene blue was evaluated using a batch approach, followed by examination by UV-Vis spectrophotometry. The adsorption data will then be analyzed for kinetic performance. The findings indicated that the methylene blue adsorption capability of natural clay reaches 72.51%. The kinetic investigation of methylene blue adsorption utilizing natural clay indicated that the adsorption process conformed to the Pseudo Second Order kinetic model.

Kinetics, thermodynamics, and equilibrium evaluation of adsorptive removal of methylene blue onto natural illitic clay mineral

The application of natural clay as an adsorbent has been widely used. This is supported by the porous surface texture of the clay. However, some treatments are needed to remove impurities in natural clay before using it as an adsorbent. The common effort is to activate it with acid. This research studied the effect of hydrochloric acid concentration on the adsorption capacity of methylene blue dye. The concentrations of hydrochloric acid used were 2, 3, and 4 M. Characterization was carried out with IR, XRD, and SEM-EDX spectroscopy to see the differences in ONC characters before and after adding hydrochloric acid. The characterization results showed that ONC contained montmorillonite and quartz, and an increase in base distance was directly proportional to the increase in the concentration of hydrochloric acid used. High concentrations of hydrochloric acid caused excessive dealumination and deionization. The dealumination process was supported by IR data where there was a shift in wavenumber in the Al-O stretching vibration region from 796 cm–1 to 794 cm–1; the sharper the vibration in the Si-O region (488-468 cm–1); there was also an increase in the Si/Al ratio of pure ONC from 1.7497 to 2.2970 for 3 M ONC-HCl. The concentration of hydrochloric acid did not significantly affect the capacity of ONC as an adsorbent for methylene blue. The adsorption capacity of pure ONC obtained was 4.97215 mg/g, while for ONC-HCl 3 M was 4.97746 mg/g.

Determination of affecting parameters on removal of methylene blue dyestuff from aqueous solutions using natural clay: Isotherm, kinetic, and thermodynamic studies

This study aims to evaluate the technical feasibility to apply natural clay from Fez area as a low cost alternative adsorbent to remove dyes from contaminated waters. Methylene blue (MB) and congo red (CR) are used here as representatives of cationic and anionic dyes normally present in wastewater from textile industry. This material was characterised by different physical-chemical methods, including BET, X-ray fluorescence and pHPZC. Additionally, the influence of operating conditions such as contact time, adsorbent dosages and pH were evaluated. Experimental results show that the adsorption processes takes place very rapid, reaching the equilibrium at 30 and 45 min for MB and CR, respectively. Maximum adsorption capacities result to be pH-depends. Hence, MB adsorption is favoured under basic pH conditions, whereas CR does it at acid pH. A pseudo-second-order kinetic model provides the best fit to the experimental data of MB and CR adsorption. Adsorption data are better described by Langmuir and Toth isotherm models. Adsorption occurs with a maximum monolayer adsorption capacity of 195 and 185 mg g-1 for MB and CR, respectively. Experimental results indicate that the Moroccan clay could be used as a potential adsorbent for the elimination of dyes from contaminated waters, at a lower cost.

Adsorption thermodynamics of cationic dyes (methylene blue and crystal violet) to a natural clay mineral from aqueous solution between 293.15 and 323.15 K

In this work, the efficiency of the adsorptive removal of the organic cationic dye methylene blue (MB) from polluted water was examined using three materials: natural clay (zeolite), Zn-Fe layered double hydroxide (LDH), and zeolite/LDH composite. These materials were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) diffraction (XRF), low-temperature N2 adsorption, pore volume and average pore size distribution and field emission scanning electron microscopy (FE-SEM). The properties of the applied nanomaterials regarding the adsorption of MB were investigated by determining various experimental parameters, such as the contact time, initial dye concentration, and solution pH. In addition, the adsorption isotherm model was estimated using the Langmuir, Freundlich, and Langmuir–Freundlich isotherm models. The Langmuir model was the best-fitting for all applied nanomaterials. In addition, the kinetics were analyzed by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, and the pseudo-second-order model was an apparent fit for all three applied nanomaterials. The maximum Adsorption capacity toward MB obtained from the materials was in the order zeolite/LDH composite > zeolites > Zn-Fe LDH. Thus, the zeolite/LDH composite is an excellent adsorbent for the removal of MB from polluted water.

Adsorption of methylene blue dye from aqueous solutions onto natural clay: Equilibrium and kinetic studies

The ability of Natural Muscovite Clay (NMC) to adsorb Methylene Blue (MB) as a dye widely used in the industrial sector was investigated, and the adsorption process was interpreted at the molecular scale through computational modelling. After the characterisation of NMC, the effect of adsorbent mass (5–40 mg), contact time (1–60 min), solution pH (3.7-11.78), stirring speed (100–900 rpm), initial MB concentration (15–80 mg.L-1), and temperature (293.15-333.15 K) on the adsorption efficiency were inspected in the batch mode. The results showed that the basic pH, high stirring speed, and low temperature were the favourable conditions for the MB adsorption onto NMC. The adsorbed quantity Qe,exp of MB dye was found to be 59.828 mg.g-1 for the initial concentration of 80 mg.L-1 at 293.15 K using an NMC mass of 20 mg. The obtained values of thermodynamic parameters suggested that the removal of the MB dye was exothermic, and physical in nature. The adsorption isotherm of the MB/NMC system was analysed according to the statistical physics approach using the Levenberg-Marquardt iterating algorithm and showed a best fitting with the monolayer model with one energy. The analysis of kinetic data showed that the external diffusion and intra-particle diffusion steps have occurred simultaneously and contributed to the control of the adsorption rate of the MB dye onto NMC. The computational modelling of interactions between the MB molecule and the muscovite, kaolinite, and quartz minerals were examined according to the Monte Carlo simulation (MCS) and showed an ability of the dye molecule to be adsorbed onto the surface of these minerals. The calculated adsorption energies ranged between -2.23×104 and -1.10×104 Kcal.mol-1 reflected the stability and the spontaneity of the adsorption process. So, the surface of clay minerals (i.e. muscovite and kaolinite) was more favourable to the adsorption of the MB molecule.

Local natural clay from Topkhana (Sulaimani district, Kurdistan region of Iraq) was characterized with XRD, XRF, FT-IR, and gas adsorption analyzer. The clay sample was dominated by saponite with minor amounts of chlorite. The clay was examined for its efficiency to adsorb and remove methylene blue (MB) from clinical laboratory wastewater by a batch method. The effects of pH, temperature, clay dosage, and initial MB concentration on the adsorption efficiency were investigated. The equilibrium experimental data were analyzed using Langmuir, Freundlich, Temkin, and Redlich-Peterson (R-P) isotherms. Most of the MB adsorption could be explained by cation exchange. The saponite, therefore, was the most important component in the clay. The rate of the adsorption process was found to follow pseudo-second-order kinetics. The conventional linear least squares method was compared with the more accurate method of non-linear curve fitting for the determination of isotherm and kinetic model parameters. Two error functions (the sum of the squared residuals and the correlation of determination) were used to evaluate the linear and non-linear regression analysis applied to the experimental data. Equilibrium thermodynamic parameters indicated a spontaneous and endothermic adsorption process.

The present research work revolves around the evaluation of the elimination of the cationic dye methylene blue (MB) from an aqueous solution by the exploitation of natural clay (TMG) from South-East Morocco. Several physicochemical techniques were used to characterize our TMG adsorbate, namely, X-ray diffraction, Fourier transform infrared absorption spectroscopy, differential thermal analysis, thermal gravimetric analysis, and zero charge point (pHpzc). The morphological properties and elemental composition of our material were identified using scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer. The batch technique was used under different operating conditions to produce quantitative adsorption, namely, the amount of adsorbent, dye concentration, contact time, pH, and solution temperature. The maximum adsorption capacity of MB on TMG was 81.185 mg g-1 for a concentration of 100 mg L-1 MB at pHinitial = 6.43 (no initial adjustment of the pH-value was performed), temperature 293 K, and 1 g L-1 adsorbent. The adsorption data were examined by Langmuir, Freundlich, and Temkin isotherms. The Langmuir isotherm provides the best correlation with the experimental data, and the pseudo-second-order kinetic model is more appropriate for the adsorption of the MB dye. The thermodynamic study of MB adsorption indicates that the process is physical, endothermic, and spontaneous. The Box-Behnken method was applied to identify the optimal conditions for MB removal in the design of batch experiments. The parameters examined result in >99% removal. The TMG material's regeneration cycles and low cost ($0.393 per gram) show that it is both environmentally friendly and very effective for dye removal in the various textile sectors.

Physico-chemical characterization and valorization of swelling and non-swelling Moroccan clays in basic dye removal from aqueous solutions

This study explores the effect of suppressed surface charges on the sedimentation behaviour and fabric of kaolinite clay. In particular, sedimentation behaviours were compared between negatively charged natural kaolin clays and surface-treated and hence electrically suppressed kaolin clays by methylene blue adsorption. The results clearly indicate that the negative surface charge impeded the sedimentation rate of kaolin by resisting particle aggregation. Such an effect appeared the most significant when the surrounding pH was less than the isoelectric point (IEP) of the mineral edges. Under a pH less than IEP, the flocculation time and the final void ratio remarkably dropped after the negative charge neutralisation. This was also corroborated by the scanning electron microscopy images, which further revealed the fabric transition from an edge-to-face flocculated structure to a face-to-face aggregated structure due to the absence of interparticle electrical forces. Conversely, there was no significant fabric change at pH higher than or near the IEP, even though the sedimentation behaviours were accelerated by forming larger flocs. This study imparts important insights into the fundamentals of microstructure and resulting sedimentation behaviour of clayey soils and how they can be changed in electrically neutralised clay.