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4-Hydroxybenzoic acid has vivid applications in the polymer, pharmaceutical, cosmetic, and food industries. Therefore, it is worth separating 4-hydroxybenzoic acid from effluent streams of different industries such as the olive oil mill, pulp and paper, and wine industry. Reactive extraction is an efficient and economic technique for the separation of carboxylic acids. The experiments for the separation of 4-hydroxybenzoic acid from aqueous solution were performed using tri-n-butylphosphate (TBP) in toluene and petroleum ether at 298 K. The investigations were quantified in terms of the distribution coefficient (K D), extraction efficiency (E %), loading ratio (Z), and equilibrium complexation constant (K E). The maximum E % and K D values were 97.14% and 24.84 in toluene and 95.14% and 15.55 in petroleum ether with TBP, respectively. The TBP–toluene system was found better than the TBP–petroleum ether for the separation of 4-hydroxybenzoic acid. The minimum solvent-to-feed ratio and the number of stages for the extraction process were also calculated, and the number of stages was seven for the TBP–toluene system and six for the TBP–petroleum ether system for a maximum TBP concentration of 0.758 mol kg–1.

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Ipomoea Carnea is a wild shrub, and because of its abundance, it was chosen as precursor for making activated carbon. Adsorbent preparation method involved the impregnation of dried precursor with zinc chloride followed by activation at 500°C. Surface morphology of prepared adsorbent was compared with the raw Ipomoea Carnea by Scanning Electron Microscope analysis. Batch adsorption studies were carried out to understand the effect of parameters like, metal initial concentration, contact time, adsorbent dose and pH on percent removal of cadmium. More than 96% removal of Cd(II) was obtained at the adsorbent dose of 0.3 g/L in 20 minutes at pH 6. Experimental data were fitted to isotherm and kinetic models to understand the mechanism of adsorption. Adsorption of Cd(II) onto raw Ipomoea Carnea followed the Langmuir isotherm, whereas adsorption onto activated Ipomoea Carnea followed the Freundlich isotherm. Kinetic study reveal that the experimental data of adsorption of Cd(II) onto activated Ipomoea Carnea followed the second order kinetic.