Dye removal by adsorption on KOH-modified activated carbon obtained from biomass

In this study, chitosan nanoparticles (ChNs) were used as an adsorbent for single and simultaneous uptake of cationic (methylene blue (MB)) and anionic (methyl orange (MO)) dyes. ChNs were prepared based on the ionic gelation method using sodium tripolyphosphate (TPP) and characterized by zetasizer, FTIR, BET, SEM, XRD, and pHPZC. The studied parameters that affect removal efficiency included pH, time, and dyes' concentration. The results showed that in single-adsorption mode, the removal of MB is better in alkaline pH, contrary to MO uptake which presents higher removal efficiency in acidic media. The simultaneous removal of MB and MO from the mixture solution by ChNs could be achieved under neutral conditions. The adsorption kinetic results showed that adsorption of MB and MO for both single-adsorption and binary adsorption systems comply with the pseudo-second-order model. Langmuir, Freundlich, and Redlich-Peterson isotherms were used for the mathematical description of single-adsorption equilibrium, while non-modified Langmuir and extended Freundlich isotherms were used to fit the co-adsorption equilibrium results. The maximum adsorption capacities of MB and MO in a single dye adsorption system were 315.01 and 257.05 mg/g for MB and MO, respectively. On the other hand, and for binary adsorption system, the adsorption capacities were 49.05 and 137.03 mg/g, respectively. The adsorption capacity of MB decreases in solution containing MO and vice versa, suggesting an antagonistic behavior of MB and MO on ChNs. Overall, ChNs could be a candidate for single and binary removal of MB and MO in dye-containing wastewater.

Activated carbon (AC) was prepared from Lapsi seed stone by chemical activation with Potassium hydroxide at 400°C. The AC was characterized by pH, moisture content, Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), methylene blue (MB) and iodine (I2) number. FT-IR spectra indicated the presence of various oxygen containing functional groups on the surface of AC. SEM images show the highly porous characteristics of AC with full of cavities. The Iodine number of AC revealed that the AC was found to be highly micro-porous. The adsorption of methylene blue by prepared AC was analyzed by the Langmuir and Freundlich adsorption isotherms. The data fitted well to the Langmuir isotherm with monolayer adsorption capacity 158 mg/g. The analysis showed that the AC prepared from Lapsi seed stone activated with potassium hydroxide could be a low-cost adsorbent with favorable surface properties. DOI: http://dx.doi.org/10.3126/jie.v9i1.10673Journal of the Institute of Engineering, Vol. 9, No. 1, pp. 79–88

Sustainable electrochemical synthesis of natural starch-based biomass adsorbent with ultrahigh adsorption capacity for Cr(VI) and dyes removal

We investigate the removal of methyl orange (MO) and methylene blue (MB) from aqueous solution by montmorillonite-pillared graphene oxide (MGO). Experimental conditions were used that evaluate the potential of MGO in removing anionic and cationic dyes in single and binary systems, and we investigated the uptake capacity of MGO toward organic dye as a function of different pH, adsorbent dosage, temperature, and adsorption time. In the single system, the Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and calculate the isotherm constants. Moreover, the pseudo-first-order and pseudo-second-order kinetic models were applied to study the mechanism of MGO adsorbing dyes. Thermodynamic studies demonstrated that the adsorption of MO and MB onto MGO was feasible and spontaneous. In the binary system, the adsorption capacities of MO and MB by MGO were dramatically higher than those in a single system. Therefore, through the recorded adsorption results under different conditions, we could illustrate that the MGO was absolutely used as an adsorbent to be capable of simultaneous removals of MO and MB.

Ice- and MOF-templated porous carbonaceous monoliths for adsorptive removal of dyes in water with easy recycling

Synthesis of zirconium-based metal-organic framework under mild conditions and its application to the removal of cationic and anionic dyes from wastewater

In this work, mesostructured metal-organic frameworks (MOFs) of MIL-101-Crs with different specific surface areas were synthesized successfully under solvothermal conditions using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) as a structural template. It was found that crystallinity degrees, specific surface areas, and pore size distributions strongly depended on the loading of CTAB. Nitrogen adsorption and positron annihilation lifetime spectroscopy (PALS) results showed that the mean mesopore size increased with loading more CTAB due to the formation of larger templated mesopores. Although Langmuir adsorption of both methylene blue (MB) and methyl orange (MO) was confirmed in MIL-101-Crs, the experimental results showed different adsorption behaviors for them depending on the dye molecular size, pore structure, and charge properties of dye molecules/MOFs in solution. The MB molecules were found to be mainly adsorbed in the interspaces between grains and the templated mesopores, whereas the MO molecules were adsorbed in the inherent pores as well as the templated ones in MOFs due to the unsaturated metal sites' electrostatic attraction on them. Remarkably, MO adsorption capacity was observed to be proportional to the specific surface area, which allowed one to get a good linear fitting of experimental data. Interestingly, the good consistence between the fitting experimental parameter, that is, the number of adsorbed MO-s per unit specific surface area, and the calculated one according to our rough estimation strongly suggests that MO-s are electrostatically attracted and rotating around the unsaturated metal sites on MOFs' inner surfaces, which exclude other MO-s to be adsorbed around due to the "hindering effect" of the rotating motion.

Optimal activated carbon production from corn pericarp: A life cycle assessment approach

Fabrication and characterization of sodium alginate and polyamidoamine dendrimer bio-nanocomposites modified by in-situ synthesis of ZIF-67 and study on highly selective adsorption performance.

This study has developed an innovative and environmentally friendly approach for the removal of methylene blue (MB) dye by natural shells (NShs) chemically modified with levulinic acid (LA). Almond shell (ASh), walnut shell (WSh), and apricot kernel shell (AKSh) were used as waste fillers. The adsorption behavior of MB onto the biosorbents was investigated with respect to parameters such as sorbent dosage (0.4–6 g/L), pH (3–10), initial dye concentration (10–500 mg/L), and temperature (25–65 °C). The biosorbents were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analysis. The isotherm and kinetic adsorption data can be said to fit the Freundlich isotherm model and the pseudosecond-order model, respectively. The maximum adsorption capacity (qmax) of LA-modified walnut shell (LA-WSh), almond shell (LA-ASh), and apricot kernel shell (LA-AKSh) calculated by the Langmuir equation at 25 °C was 294.1, 270.2, and 180.0 mg/g, respectively. The results of thermodynamic analysis showed that adsorption was feasible, endothermic, and spontaneous.

Performance evaluation of cement–carbon composite for adsorptive removal of acidic and basic dyes from single and multi-component systems

Adsorption of indigo carmine (IC), methyl orange (MO) and methylene blue (MB) onto hydroxyapatite–chitosan–montmorillonite (HAP–CTS–Mt) film was studied. The influence of contact time, solution pH, initial dyes concentration, amount of HAP–CTS–Mt film and solution temperature were scrutinized. Characteristic bands and structure of HAP–CTS–Mt film were determined using Fourier infrared spectroscopy and X-ray diffraction. The optimal concentrations of IC, MO, and MB were 20 mg/L, 50 mg/L, and 20 mg/L, respectively. Optimal dose of HAP–CTS–Mt was 0.2 g/L for IC and MB and 0.5 g/L for MO. The adsorption process of IC, MO, and MB using HAP–CTS–Mt film was verified by Langmuir isotherm model with maximum adsorption capacities of 243.18 mg/g, 137.5 mg/g and 168.52 mg/g for IC, MO, and MB, respectively. The adsorption kinetics of IC, MO, and MB onto HAP–CTS–Mt film were well fitted by the pseudo-second-order model. The HAP–CTS–Mt thin film can be employed as an efficient adsorbent for removal of IC, MO, and MB dyes from aqueous solutions.

Graphene oxide-wrapped magnetite nanoclusters: A recyclable functional hybrid for fast and highly efficient removal of organic dyes from wastewater

In this study, corn cobs and corn roots, agricultural by-products and wastes, were used as precursors for preparation of powder activated carbons (PAC-CC and PAC-CR) by chemical activation with H 3 PO 4 . Functional groups on the surface of both adsorbents were determined by using ATR−FTIR spectroscopy, while their specific surfaces area were calculated using methylene blue adsorption method . Removal of Crystal Violet (CV) dye from aqueous medium onto both adsorbents was carried out at optimal pH of 10. The pseudo-first order and pseudo-second-order models were used to study adsorption kinetics. The Langmuir and Freundlich, isotherm models were employed to analyze the adsorption isotherm. CV dye molecules-activated carbon surface interaction revealed CV dye’s monolayer formation over activated carbon’s surface and the involvement of chemisorption, as verified by Langmuir isotherm model and pseudo-second order model, respectively. Langmuir maximum adsorption capacity of PAC-CC and PAC-CR for CV dye were 41.80 mg/g and 35.92 mg/g, respectively. From these results, it can be concluded that the activated carbon prepared from corn cobs or roots as precursor can be used as adsorbent for successful removal of dyes in an aqueous medium.

In this study, the silver nanoparticles (AgNPs) as an eco-friendly, efficient and low-cost adsorbent was synthesized from Chenopodium botrys extract. Characteristics of the prepared adsorbent were investigated using scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDAX). According to the particle size distribution, the average size of AgNPs was obtained 11.9 nm. AgNPs were used for methyl blue (MB) and methyl orange (MO) removal from aqueous solution. Maximum removal percentages of 97.50 and 95.00 was obtained under optimum conditions, including contact time of 25 min, pH = 10, adsorbent dosage of 0.9 g, and dye concentration of 30 mg/L for MB and MO, respectively. Langmuir isotherm indicated the best results of adsorption related to the MB and MO with the maximum adsorption capacity of (qmax) 90.09 and 80 mg g−1 for MB and MO, respectively. The kinetics study showed that the results were fitted to the pseudo-second-order model with the coefficient of determination (R2) of 0.9984 and 0.9919 for MB and MO, respectively. The process of removal can be also by adsorption of dye molecule on the surface of Ag-NPs and also may be due to the removal of dye molecules by hydroxyl radicals generated by the NPs effect on water molecules in the presence of light. The proposed adsorbent with its great properties can be used to remove contaminants from industrial wastewater before discharge to the environment.