Polypyrrole-coated halloysite nanotube clay nanocomposite: Synthesis, characterization and Cr(VI) adsorption behaviour

Rapid and efficient removal of fluoride ions from aqueous solution using a polypyrrole coated hydrous tin oxide nanocomposite

“…As the adsorbent outer surface become loaded with fluoride ions, the process in the later stages become controlled by intra-particle diffusion through the pores for uptake at the interior surface of the adsorbent (second slightly curved section) until equilibrium is attained (third and last linear section). The k int1, k int2 and k int3 are intraparticle diffusion rate constants for the consecutive three linear sections of the curve of the higher concentrations (15 and 20 mg/L), whereas due to very fast kinetics, at lower F À concentrations (5 and 10 mg/L), only two linear sections (k int1 and k int2 ) were observed indicating the final equilibrium stage combined with intraparticle pore diffusion [30]. The k int values were calculated from the initial linear portion of the curves and are presented in Table S3 (Supplementary table).…”

“…For PPy/HSnO NC 3 ( Fig. 5(b)), the first initial weight loss of $10.8% was observed up to 200°C due to the loss of water molecules [30] and after that major weight loss of about $65.2% occurred in the range of 200-590°C. This mass loss of $65.2% might be due to the thermal decomposition of PPy due to the breaking of the bond affinity between the PPy and doped Cl À ion in the polymers [27].…”

“…The non-linear [35] and linear [30] forms of Langmuir isotherm are given by Eqs. (12) and (13) respectively:…”

“…The non-linear [35] and linear [30] forms of Freundlich isotherm expressed by Eqs. (15) and (16) respectively were also applied to isotherm data to evaluate its applicability: …”

Properties and applications of halloysite nanotubes: recent research advances and future prospects

“…Duan et al (2010) also proposed a method for the removal of Cr(VI) by Hal materials modified with γ-mercaptopropyltrimethoxy silane, however, the Cr(VI) adsorption capacity was somewhat low, 2.79 mg/g, and the mechanism of the reaction of silane with Cr(VI) anions was not given. Moreover, Ballav et al (2014) investigated the performance of polypyrrole-coated Hal as adsorbent for Cr(VI), and found that the Cr(VI) adsorption on polypyrrole-coated Hal was spontaneous and endothermic in nature; the maximum adsorption capacity was as high as 149.25 mg/g at pH 2.0, and some part of Cr(VI) was reduced to Cr(III) by electron-rich polypyrrole moiety. Organic contaminants are also widely produced from industrial processes, and many of them are very harmful to human beings and microorganisms.…”