Chromium removal from aqueous solution by a PEI-silica nanocomposite

It is essential and important to determine the adsorption mechanism as well as removal efficiency when using an adsorption technique to remove toxic heavy metals from wastewater. In this research, the removal efficiency and mechanism of chromium removal by a silica-based nanoparticle were investigated. A PEI-silica nanoparticle was synthesized by a one-pot technique and exhibited uniformly well-dispersed PEI polymers in silica particles. The adsorption capacity of chromium ions was determined by a batch adsorption test, with the PEI-silica nanoparticle having a value of 183.7 mg/g and monolayer sorption. Adsorption of chromium ions was affected by the solution pH and altered the nanoparticle surface chemically. First principles calculations of the adsorption energies for the relevant adsorption configurations and XPS peaks of Cr and N showed that Cr(VI), [HCrO4](-) is reduced to two species, Cr(III), CrOH2+ and Cr3+, by an amine group and that Cr(III) and Cr(VI) ions are adsorbed on different functional groups, oxidized N and NH3+

Adsorption of phenolic compounds from aqueous solutions using functionalized SBA-15 as a nano-sorbent

AbstractAmino functional mesoporous silica SBA-15 materials have been prepared as efficient adsorbents for halophenols in wastewater. The organic–inorganic hybrid material was obtained using successive grafting procedures of SBA-15 silica with 3-aminopropyl-trimethoxysilane (NH2–SBA-15). The comparison of adsorption of halophenols on untreated mesoporous SBA-15 and NH2–SBA-15 is studied. It is found that NH2–SBA-15 shows significant adsorption for halophenols. The samples were characterized by X-Ray Diffraction (XRD), nitrogen adsorption-desorption isotherms, Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FT–IR). Batch adsorption studies have been carried out to study the effect of various parameters, such as contact time, pH, adsorbent dose and initial adsorbate concentration. The equilibrium adsorption data of halophenols onto NH2–SBA-15 were analyzed using Freundlich and Langmuir adsorption isotherms. From the sorption studies it was observed that the uptake of 4-chlorophenol (CP) was higher than 4-bromophenol (BP) and 4-iodophenol (IP)

A zinc oxide-coated nanoporous carbon adsorbent for lead removal from water: Optimization, equilibrium modeling, and kinetics studies

A zinc oxide-coated nanoporous carbon sorbent was prepared by acid modification and ZnO functionalization of mesoporous carbon. The synthesized materials, such as mesoporous carbon, oxidized mesoporous carbon and zinc oxide-coated nanoporous carbon, were characterized by nitrogen adsorption-desorption analysis, Fourier transform infrared spectra, scanning electron microscopy, and transmission electron microscopy. ZnO on oxidized mesoporous carbon gradually increased with increase in the number of cycles. Furthermore, the effects of agitation time, initial metal ions concentration, adsorbent dose, temperature and pH on the efficiency of Pb(II) ion removal were investigated as the controllable factors by Taguchi method. The value of correlation coefficients showed that the equilibrium data fitted well to the Langmuir isotherm. Among the adsorbents, zinc oxide-coated nanoporous carbon showed the largest adsorption capacity of 522.8 mg/g (2.52 mmol/g) which was almost close to that of the zinc oxide-coated (2.38 mmol/g), indicating the monolayer spreading of ZnO onto the oxidized mesoporous carbon. The results of the present study suggest that ZnO-coated nanoporous carbon can be effectively used for Pb(II) adsorption from aqueous solution, whereas a part of acidic functional groups may be contributed to binding the Pb(II) for the oxidized mesoporous carbon and mesoporous carbon. Kinetic studies indicated that the overall adsorption process of Pb(II) followed the pseudo-second-order model. The ZnO-coated nanoporous carbon was regenerated and found to be suitable of reuse of the adsorbent for successive adsorption-desorption cycles without considerable loss of adsorption capacity