In the present study, the pH point of zero charge (pHpzc) was determined for concrete particles adsorbent. The Mass Titration (MT) Method was adopted, and the adsorbent was used to remove the fluoride from water. The pH of point zero charge of concrete adsorbent was found to be 12. The data of pHpzc of the adsorbents give information about the attraction and repulsion between adsorbents and adsorbates. The mass titration technique was found to be an easy way to determine the pHpzc of the studied material.

Determination of Point of Zero Charge (PZC) of Concrete Particles Adsorbents

Aggressive industrial development over the last century involved different heavy metals being used, including high quantities of molybdenum, which need to be treated before discharge in industrial waters. Molybdenum’s market price and industrial applicability make its recovery a big challenge. In the present study the possibility to recover molybdenum ions from aqueous solutions by adsorption on a composite material based on silica matrix and iron oxides—SiO2FexOy—was evaluated. Tests were performed in order to determine the influence of adsorbent material dose, initial solution pH, contact time and temperature over adsorption capacity of synthesized adsorbent material. For better understanding of the adsorption process, the obtained experimental data were modelled using Langmuir, Freundlich and Sips adsorption isotherms. Based on the obtained data, it can proved that the Sips isotherm was describing with better orderliness the studied process, obtaining a maximum adsorption capacity of 10.95 mg MoO42− for each gram of material. By modelling the studied adsorption process, it was proven that the pseudo-second order model is accurately describing the adsorption process. By fitting experimental data with Weber-Morris model, it was proven that MoO42− adsorption is a complex process, occurring in two different steps, one controlled by diffusion and the second one controlled by mass transfer. Further, studies were performed in order to determine the optimum pH value needed to obtain maximum adsorption capacity, but also to determine which are the adsorbed species. From pH and desorption studies, it was proven that molybdate adsorption is a physical process. In order to establish the adsorption mechanism, the thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were determined.

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Molybdate Recovery by Adsorption onto Silica Matrix and Iron Oxide Based Composites

Zirconium oxide nanoparticles (ZrO2NPs) were green synthesized for the first time using an aqueous peppermint extract as a precipitating and capping agent. Addition of the extract to Zr4+ solution was followed by calcination of the resulting precipitate at 570 and 700 °C to form ZrO2NPs570 and ZrO2NPs700, respectively. These oxides were characterized using X-ray diffraction, transmission electron microscopy, and BET surface area analysis, and used as adsorbents for cobalt ions (Co2+) in water. The effects of pH, initial Co2+ concentration, ZrO2NPs mass, and contact time on adsorption efficiency were studied. Characterization results showed formation of cubic ZrO2 with average crystallite sizes (XRD data) of 6.27 and 7.26 nm for ZrO2NPs570 and ZrO2NPs700, respectively. TEM images of the two oxides exhibited nearly spherical nanoparticles and BET surface area measurements indicated the formation of mesoporous oxides having surface areas of 94.8 and 62.4 m2/g, respectively. The results of the adsorption study confirmed that the synthesized ZrO2NPs can be efficiently used for the adsorption of Co2+ from water. The uptake of Co2+ from the treated solution is favored at pH values higher than its point of zero charge (6.0). In addition, the adsorption of Co2+ by ZrO2 follows a pseudo-second order kinetics (R2 = 1.0) and can be explained by the Langmuir adsorption isotherm (R2 = 0.973).

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Peppermint-Mediated Green Synthesis of Nano ZrO2 and Its Adsorptive Removal of Cobalt from Water

Synthesis of γ-graphyne by modified mechanochemistry with enhanced adsorption of organic dyes

Enhancing sorption capacity of methylene blue dye using solid waste of lemongrass biosorbent by modification method

As a regulated contaminants, fluorine compounds impact the health of millions of persons around the world. Adsorption method is employed to remove fluoride ions from a synthetic water using concrete waste materials as a low cost adsorbent and to evaluate its feasibility as an alternative agent to eliminate fluoride ions in aqueous solution. Influence of pH, concrete particles dosage, agitation speed, fluoride initial concentration and contact time on F− removal were investigated by using batch mode. Fluoride removal has been obtained over a wide range (3-11). The rate of adsorption was rapid at the first 4 hours, while the equilibrium has been reached within 9 hrs. The desorption study revealed that fluoride adsorption onto concrete particles was chemical in nature. The kinetic of adsorption was fitted well with second-order rate model, while the adsorption behavior obeyed Freundlich model. This study obviously presents the applicability of concrete particles as low cost adsorbent to eliminate fluoride from water.

Geomaterials as Cost Effective Sorbent to Remove Fluoride from Water

In the present study, fluoride ions removal from aqueous solution was studied by adsorption method, using concrete particles as adsorbent. The concrete particles were collected from two different local demolished buildings. It was used batch and continuous systems in this study, the continuous system includes fixed and fluidized bed reactor. In batch system, the effects of many parameters was investigated like pH (3–12), initial fluoride concentration (5–25 mg/l), adsorbent dose (0.5–5 g/100 ml) and contact time (2–9) h to determine the best conditions for fluoride removal. In the continuous mode, several operating conditions were investigated like flow rate (6, 9 and 12 l/h), bed depth (6, 12, 20 cm) and inlet fluoride concentration (10, 15 and 20 mg/l). Thomas and Yoon–Nelson models were adopted using the data of breakthrough curves of optimal operating conditions, and there was a good fitting between the theoretical and the experimental data. Adsorption capacity of the concrete particles was found to be 0.818 mg/g and 0.73 mg/g for fluidized and fixed bed, respectively for the optimum conditions. The adsorption study of concrete particles showed good performance in removing fluoride from aqueous solution.

Concrete Particles as Low-Cost Adsorbent for Fluoride Removal using Batch and Continued Systems

In the present study, fluoride ions removal from aqueous solution was studied by adsorption using a new low cost adsorbent which is concrete particles in continuous systems. The continuous systems included fixed and fluidized bed reactor. several operating conditions were used for both of fixed and fluidized column; flow rate (6,9 and 12) l/h, bed depth (6,12,20) cm inlet fluoride concentration (10,15 and 20) mg/l. Thomas and Yoon–Nelson models were used in this study using the data of breakthrough curves for the optimal conditions (bed height of 20 cm, influent flow rate of 6 l/h and inlet fluoride concentration of 10 mg/l). Adsorption capacity of the concrete particles was found to be 0.818 mg/g and 0.73 mg/g for fluidized and fixed bed respectively for the optimum conditions. The adsorption test using concrete particles adsorbent revealed the good performance of removing fluoride from aqueous solution.

Ebtehal A. Al-Maliky

Papers

Determination of Point of Zero Charge (PZC) of Concrete Particles Adsorbents

Geomaterials as Cost Effective Sorbent to Remove Fluoride from Water

Concrete Particles as Low-Cost Adsorbent for Fluoride Removal using Batch and Continued Systems

Concrete particles for fluoride removal using continued fixed-bed and fluidized-bed systems