Exploring the structural characteristics and dye removal capabilities of powder-, granule- and film- shaped magnetic activated carbon derived from Oleaster seed.

Dye pollution in water caused by excessive discharge of industrial effluent has become a major environmental problem in recent decades because of its irreversible effects on human health. In this study, low-cost carbon-based adsorbents synthesized from Oleaster seed (OS) were prepared in three forms of powder (PAC), film (FAC), and granule (GAC) and used for the removal of methylene blue dye. The properties of the synthesized adsorbents were characterized by SEM-EDX, BET, XPS and FTIR analyses. The maximum adsorption capacity (qmax) of PAC, FAC, and GAC adsorbents were obtained as 68.49, 32.25, and 15.10 mg/g, respectively at the optimum experimental conditions of pH = 10, adsorbent dosages of 0.5, 1, and 2 g/l, contact times of 60, 90, and 120 min, dye concentration of 10 mg/L, and temperature of 25°C. The Langmuir isotherm well described the equilibrium data for all three adsorbents. The pseudo-second-order kinetic model provided the best fit with the adsorption data obtained from all three adsorbents. Adsorption occurred spontaneously through a combination of chemical and physical mechanisms, with a thermodynamically exothermic process. The desorption experiments demonstrated that all the adsorbents have substantial potential for recovery. The novel activated carbon/alginate composite films are proposed as more promising biosorbents to remove MB dye from the aquatic environment compared to GAC adsorbents.

Arsenate removal from contaminated water using Fe2O3-clinoptilolite powder and granule.

Natural clinoptilolite (Clin) was modified with iron oxide using three different methods including precipitation, wet-impregnation and ion-exchange and then the modified adsorbent with highest As(V) removal efficiency was encapsulated into Alginate by a simple cross-linking method to obtain Fe-Clin granules. The surface morphology and chemical composition of the Fe-Clin sorbents were characterized by scanning electron microscope and X-ray diffraction analysis. The selected Fe-Clin powders and granules possessed enhanced affinity towards the highly toxic arsenic pollutant in a very short time. Batch adsorption experiments showed that the Fe-Clin adsorbent can be widely used within a wide range of pH (2-9). In addition, to reach a high removal percentage (over 90%) of As(V), the optimum dosage of powder and granule shaped adsorbents was obtained as 0.1 and 0.6 g L-1, respectively. Both adsorbents could successfully remove As(V) in a very short amount of time as 20 and 30 min in the case of powders and granules, respectively. The maximum adsorption capacity of Fe-Clin granules evaluated by using Langmuir adsorption isotherm was found to be 11.17 mg g-1. By testing the granules in a circulated fluidized column experiment, it was demonstrated that Fe-Clin granules could remove As(V) up to an acceptable level (93%) within 10 min. This study demonstrates that Fe-Clin granules, obtained by exploiting natural clinoptilolite, iron oxide and alginate, are efficient, sustainable and fairly cheap adsorbents for the removal of arsenate from the aquatic environment in a very short contact time.

The role of the hydrogen bond in dense nanoparticle-gas suspensions.

The effect of surface characteristics on the interaction between nanoparticles and their agglomeration in dense gas suspensions is still not fully understood. It is known that when the surface is covered with hydroxyl groups, the interaction between nanoparticles becomes substantially stronger than in the absence of these groups; this strengthening is typically attributed to the formation of capillary bridges between the particles. However, this work shows that part of the increase of the interaction is due to the direct hydrogen bonds formed between the surfaces of the polar particles. Dry nitrogen was used to fluidize polar (hydrophilic) and apolar (hydrophobic) SiO2, TiO2 and Al2O3 particles, with a size ranging from 13 to 21 nm. The dry polar particles showed smaller bed expansion and larger minimum fluidization velocity compared to their apolar counterparts, indicating stronger interparticle forces. The results show the importance of including the formation of hydrogen bonds in the modeling of the interaction between dry and polar nanoparticles.