Water Purification of Classical and Emerging Organic Pollutants: An Extensive Review

The main techniques used for organic pollutant removal from water are adsorption, reductive and oxidative processes, phytoremediation, bioremediation, separation by membranes and liquid–liquid extraction. In this review, strengths and weaknesses of the different purification techniques are discussed, with particular attention to the newest results published in the scientific literature. This study highlighted that adsorption is the most frequently used method for water purification, since it can balance high organic pollutants removal efficiency, it has the possibility to treat a large quantity of water in semi-continuous way and has acceptable costs.

Adsorption process of tetrachloroethylene (PCE) on network growth ring

This study was undergone to investigate the adsorption characteristics of tetrachloroethylene (PCE) on water supply network growth ring. According to the chemical composition of real network growth ring, iron oxide mixture containing synthesized goethite and lepidocrocite was applied as simulated growth ring. The results demonstrate that competition could take place only between PCE and the co-present organic non-ionic compound, while inorganic salt had no discernible effect on PCE adsorption. A maximum adsorption capacity of 33.118 mg g^-1 at equilibrium was achieved. By the non-linear regression method, the equilibrium adsorption data fitted well with the Freundlich isotherm model (R² = 0.994), and the kinetic data obeyed pseudo-first order model (R² = 0.985). Thermodynamic tests indicate the spontaneous and exothermic nature of adsorption process. In addition, no significant variation between the FTIR spectra of the iron oxide mixture before and after adsorption was observed, which verifies that hydrogen bonds between PCE and mineral mixture could be neglected. An overview of the experimental results leads to the conclusion that the adsorption of PCE onto the simulate growth ring was driven by dispersion and hydrophobic interactions. As a case study, this work will provide some information about water supply securit protection.

Comparative removal of emerging contaminants from aqueous solution by adsorption on an activated carbon

Batch sorption experiments were performed to study the adsorption of six emerging pollutants from aqueous solutions using a commercial granular activated carbon as adsorbent. Caffeine, clofibric acid, diclofenac, gallic acid, ibuprofen and salicylic acid were selected as representative contaminants. The activated carbon was characterized by nitrogen adsorption at 77 K, and through the determination of point of zero charge. The effects of several operational parameters, such as pH, initial concentration of organic molecules, mass of adsorbent and contact time, on the sorption behaviour were evaluated. The contact time to attain equilibrium for maximum adsorption was found to be 40 min. The kinetic data were correlated to several adsorption models, and the adsorption mechanism found to follow pseudo-second-order and intraparticle-diffusion models with external mass transfer predominating in the first 15 min of the experiment. The equilibrium adsorption data were analysed using the Freundlich, Langmuir and Toth isotherm equation models. The similar chemical structure and molecular weight of the organic pollutants studied to make the adsorption capacity of the activated carbon used very similar for all the molecules.