Adsorption of congo red and methylene blue dyes on an ashitaba waste and a walnut shell-based activated carbon from aqueous solutions: Experiments, characterization and physical interpretations

Activated carbons were prepared from ashitaba waste and a walnut shell to study the adsorption mechanism of congo red and methylene blue dyes in aqueous solution. These adsorbents were characterized via XRD, FTIR and SEM techniques and the dye adsorption isotherms at three temperatures were quantified. A statistical physics model was applied to interpret the adsorption mechanism of tested dyes and adsorbents. Modeling results showed that these dyes were practically separated in the solution leading to an absence of the aggregation process. Adsorption orientations of dye molecules on the adsorbents changed depending on the temperature and nature of systems. The adsorption capacity of ashitaba waste activated carbon for the removal of congo red was significant thus indicating strong interactions between this dye and tested adsorbent. Calculated adsorption energy varied from 7.25 to 20.43 kJ/mol and they showed that the adsorption of both adsorbates occurred via physical interactions at different temperatures where the removal process was endothermic

Removal of captopril pharmaceutical from synthetic pharmaceutical-industry wastewaters:Use of activated carbon derived from Butia catarinensis

A high surface area activated carbon was produced from the seed of Butia catarinensis (Bc), which was utilized for removing captopril from synthetic pharmaceutical industry wastewaters. The activated carbon was made by mixing ZnCl2 and Bc at a proportion of 1:1 and pyrolyzed at 600° (ABc-600). The material was characterized by the Boehm titration, hydrophilic/ hydrophobic ratio, elemental analysis, TGA, FTIR, and N2 isotherm (surface area (SBET), total pore volume (TPV), and pore size distribution (PSD)). The characterization data showed that the adsorbent displayed a hydrophilic surface due to the presence of several polar groups. The carbon material presented a TPV of 0.392 cm3 g−1, and SBET of 1267 m2 g−1. The equilibrium and kinetics data were suitably fitted to Liu isotherm and Avrami-fractional-order. The employment of the ABc-600 in the treatment of synthetic pharmaceutical industry wastewater exhibited high effectiveness in their removals (up to 99.0 %)

A Novel Nanocomposite of Activated Serpentine Mineral Decorated with Magnetic Nanoparticles for Rapid and Effective Adsorption of Hazardous Cationic Dyes: Kinetics and Equilibrium Studies

A widely distributed mineral, serpentine, obtained from Wadi Ghadir (Eastern Desert in Egypt) was studied as a potential naturally and abundantly available source for the synthesis of an efficient adsorbent for aquatic remediation applications. A novel nanocomposite was synthesized after the exfoliation of the layered structure of serpentine by hydrogen peroxide treatment (serpentine (SP)), followed by decoration with magnetic Fe3O4 nanoparticles (MNP). The goal behind the utilization of the latter phase was to increase the environmental remediation capability and to incorporate magnetic properties at the final adsorbent, toward a better separation after the use. The fabricated composite (MNP/SP) was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The composite’s potential adsorption application toward the removal of two cationic dyes, methylene blue (MB) and malachite green (MG), was investigated. The observed adsorption kinetics was fast, and the highest uptake was observed at pH = 8, with the capacities to reach 162 and 176 mg g−1 for MB and MG, respectively, values significantly higher than various other materials tested against these two cationic dyes. Compared to hydrogen peroxide-treated serpentine, the removal efficiency of the composite was higher by 157 and 127% for MB and MG, respectively. The MB and MG were adsorbed because of the favorable electrostatic interactions between MNP/SP active sites and the cationic dyes. The close value capacities suggest that the difference in chemistry of the two dyes does not affect the interactions, with the later occurring via the dyes’ amine functionalities. With increasing ionic strength, the adsorption of the studied basic dyes was slightly decreased, suggesting only partial antagonistic ion effect. The sorbent can be easily regenerated and reused without significant deterioration of its adsorption efficiency, which makes MNP/SP a promising adsorbent for the removal of hazardous pollutants from aquatic environments

Correction: Barakat et al. Fe₃O₄ Nanoparticles Loaded Bentonite/Sawdust Interface for the Removal of Methylene Blue: Insights into Adsorption Performance and Mechanism via Experiments and Theoretical Calculations. <i>Water</i> 2022, <i>14</i>, 3491

In the original publication [...

Repurposing carbonate-based waste for producing an innovative binder: optimization and characterization

This study reports the full recycling of dolomite waste (DW) in the fabrication of a novel cementitious material through a facile and eco-efficient method. The proposed technique includes mixing different alkali-activators (i.e., NaOH and Na2SiO3) with DW powder, followed by curing at room temperature. Based on the alkali-activator type, sodium oxide concentration, and curing time, the formulated mixtures yield a wide range of compressive strengths. When DW powder is mixed with different contents of NaOH (2.5, 5, and 7.5 wt.% Na2O), the resulting hardened materials exhibited modest compressive strengths (less than 11 MPa) due to the formation of the gaylussite Na2CO3·CaCO3·5H2O phase. Concerning the other chemical activator (Na2SiO3), a significant improvement in the compressive strengths of the resulted hardened materials was detected. This was ascribed to the formation of calcium silicate hydrate, with a high binding capacity, through the exchange reaction between Na2SiO3 and CaCO3 inside DW. The sample activated with Na2SiO3 (silica modulus of 1.5) equivalent to Na2O of 7.5 wt.% offered the highest 90-day compressive strength (34 MPa). At silica modulus lower or higher than 1.5, a noticeable decrease in the performance of the hardened materials was observed, which could be attributed to the alter in binding phase composition. Overall, the present work presented a new approach in utilizing the available and low cost carbonate-based wastes as main precursors in the family of promising alkali-activated materials

A comparative study on the role of metakaolin and diatomite in the performance of eco-friendly dolomite waste–based alkali-activated binder

The production process of dolomite aggregate yields a huge content of the rejected size, namely dolomite waste. This waste causes many environmental problems including increasing the wastage area, disposal of landfill, and increasing the air pollution. This work pay attention to the sustainable disposal of this waste in the production of an innovative binder using chemical exchange reaction. This work aims to examine the role of metakaolin (MK) and diatomite (DT) in enhancing the physicochemical properties of alkali-activated binder-based dolomite waste (AADW). The DW powder was combined with varying weight percentages of MK and DT. The resultant admixtures were activated via Na2SiO3, followed by curing at room temperature. The fabricated mixtures possess a wide range of compressive strength values, dependent on the contents of the additives (MK and DT). AADW without any additives represents a compressive strength of 34.6 MPa. DT was found to have a minimal effect on early compressive strength but significantly enhanced later strength. In contrast, incorporating MK into the alkali-activated system materially improved the early compressive strength, while it recorded 28-day strengths similar in hardness to the hardened sample with DT. Specifically, AADW-DT10 and AADW-MK10, which contain 10 wt% DT and MK, respectively, exhibited 7- &amp; 28-day compressive strengths of 14.4 MPa &amp; 32.1 MPa and 57 MPa &amp; 56.2 MPa, respectively. Replacing DW with DT reduced drying shrinkage of the resultant hardened alkali-activated materials. However, incorporating MK up to 10 wt% reduced the drying shrinkage of AADW, while the sample with 15 wt% recorded the highest drying shrinkage. Nonetheless, AADW-DT exhibited lower drying shrinkage than that of AADW-MK at all curing ages up to 90 days. Overall, the result indicated that the higher reactivity and high alumina content of MK provide suitable conditions for synthesizing hardened materials with better physical and mechanical properties when compared to AADW-DT

Experimental and Theoretical Studies of Methyl Orange Uptake by Mn–Rich Synthetic Mica: Insights into Manganese Role in Adsorption and Selectivity

Manganese&ndash;containing mica (Mn&ndash;mica) was synthesized at 200 &deg;C/96 h using Mn&ndash;carbonate, Al&ndash;nitrate, silicic acid, and high KOH concentration under hydrothermal conditions. Mn&ndash;mica was characterized and tested as a new adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. Compared to naturally occurring mica, the Mn&ndash;mica with manganese in the octahedral sheet resulted in enhanced MO uptake by four times at pH 3.0 and 25 &deg;C. The pseudo&ndash;second order equation for kinetics and Freundlich equation for adsorption isotherm fitted well to the experimental data at all adsorption temperatures (i.e., 25, 40 and 55 &deg;C). The decrease of Langmuir uptake capacity from 107.3 to 92.76 mg&middot;g&minus;1 within the temperature range of 25&ndash;55 &deg;C suggested that MO adsorption is an exothermic process. The role of manganese in MO selectivity and the adsorption mechanism was analyzed via the physicochemical parameters of a multilayer adsorption model. The aggregated number of MO ions per Mn&ndash;mica active site ( n ) was superior to unity at all temperatures signifying a vertical geometry and a mechanism of multi&ndash;interactions. The active sites number (DM) of Mn&ndash;mica and the total removed MO layers (Nt) slightly changed with temperature. The decrease in the MO adsorption capacities (Qsat = n&middot;DM&middot;Nt) from 190.44 to 140.33 mg&middot;g&minus;1 in the temperature range of 25&ndash;55 &deg;C was mainly controlled by the n parameter. The results of adsorption energies revealed that MO uptake was an exothermic (i.e., negative &Delta;E values) and a physisorption process (&Delta;E &lt; 40 kJ mol &minus;1). Accordingly, the adsorption of MO onto Mn&ndash;mica was governed by the number of active sites and the adsorption energy. This study offers insights into the manganese control of the interactions between MO ions and Mn&ndash;mica active sites