Adsorptive behaviour of rutile phased titania nanoparticles supported on acid-modified kaolinite clay for the removal of selected heavy metal ions from mining wastewater

Abstract

AbstractThis study investigated the removal of metal ions pollutants in mining wastewater such as Mn (II), Fe (III), Pb (II) and Cu (II) ions by acid-activated kaolinite clay (AAC) and titanium (IV) oxide (TiO2) nanoparticles supported on the AAC (TiO2–AAC). TiO2 nanoparticles were synthesised using titanium salt precursor with leaves extract of Parkia biglobossa and impregnated on the AAC to develop TiO2-AAC as a nanoadsorbent. The AAC and TiO2–AAC nanocomposites were characterized using different analytical techniques. Actual concentrations of selected heavy metals in mining wastewater was determined prior and after treatment using the prepared adsorbents in batch adsorptive studies with atomic absorption spectrophometer. The characterisation studies confirmed that a rutile phase TiO2 was doped the on acid-activated kaolinite clay. Morphology analysis shows that the developed adsorbents were homogeneously dispersed and porous. The results of the surface area further revealed that the AAC, TiO2 and TiO2–AAC has 14.15, 10.23 and 32.98 m2/g, respectively. The percentage removal of heavy metals followed the order of TiO2–AAC > AAC due to the higher surface area and enhanced surface functionality of the former than the latter. The adsorption capacity increased from 86.13 to 91.99% (Fe (III)), 83.12 to 89.37% (Mn (II)), 68.48 to 81.95% (Cu (II)) and 29.49 to 32.39% (Pb (II)) from AAC to TiO2–AAC. The kinetic and isotherm models were best fitted by pseudo-second-order kinetics and Langmuir model. Whilst the thermodynamic investigation found that, the adsorption process was endothermic, spontaneous and chemisorption controlled. Conclusively, the TiO2–AAC nanocomposite exhibited better performance than AAC alone.