Polymeric adsorbents for oil removal from water.

In this study, the application of four synthetic resins for the removal of emulsified oil from produced water was investigated. Key experimental parameters such as adsorbent dosage, contact time, initial oil concentration and pH were evaluated for Optipore L493, Amberlite IRA 958, Amberlite XAD 7 and Lewatit AF 5. Oil removal rates upwards of 98% were achieved using AF 5, XAD 7 and L493. IRA 958 recorded very modest removal rates of less than 25%. Isotherm data were further investigated and fitted using Langmuir, Freundlich, Toth, Flory Huggins and Dubinin-Radushkevich models. The results show that the adsorption onto XAD 7 and L 493 is a multilayer adsorption process over a heterogeneous surface that is best illustrated by the Freundlich and Toth models respectively. The Dubinin-Radushkevich best described the removal using AF 5 resin that assumes that the adsorption process occurs on a heterogenous surface with a gaussian energy distribution. Kinetic studies assessing the rate of removal for each resin were conducted. Experimental results were best fitted using pseudo second order kinetics. It is concluded that XAD 7 had the highest kinetics among all tested resins. Also, AF 5 exhibited the highest adsorption capacity. Overall, the study confirmed the applicability of the resins for the removal of oil from produced water.

Influence of solution chemistry on Cr(VI) reduction and complexation onto date-pits/tea-waste biomaterials.

Tea waste (TW) and Date pits (DP) were investigated for their potential to remove toxic Cr(VI) ions from aqueous solution. Investigations showed that the majority of the bound Cr(VI) ions were reduced to Cr(III) after biosorption at acidic conditions. The electrons for the reduction of Cr(VI) may have been donated from the TW and DP biomasses. The experimental data obtained for Cr(VI)-TW and Cr(VI)-DP at different solution temperatures indicate a multilayer type biosorption, which explains why the Sips isotherm accurately represents the experimental data obtained in this study. The Sips maximum biosorption capacities of Cr(VI) onto TW and DP were 5.768 and 3.199 mmol/g at 333 K, respectively, which is comparatively superior to most other low-cost biomaterials. Fourier transform infrared spectroscopic analysis of the metal loaded biosorbents confirmed the participation of -COOH, -NH(2) and O-CH(3) groups in the reduction and complexation of chromium. Thermodynamic parameters demonstrated that the biosorption of Cr(VI) onto TW and DP biomass was endothermic, spontaneous and feasible at 303-333 K. The results evidently indicated that tea waste and date pits would be suitable biosorbents for Cr(VI) in wastewater under specific conditions.