Dynamics and Kinetics of Cupric Ion Removal from Wastewaters by Tunisian Solid Crude Olive-Oil Waste

Biosorption of copper ions with olive pomace and walnut shell

The removal of copper ions, from synthetic solutions, using walnut shell and olive pomace waste as biosorbents was studied. Synthetic copper solutions were used, and the contact time, initial pH, biosorbent dose, and initial concentration of copper ions were evaluated. The used particle size of both biosorbents was inferior to 600 µm. In the elimination of copper ions, the walnut shell reached 88% (30 min), and the olive pomace 86.5% (40 min). The maximum removal of copper ions was at pH 5 with both biosorbents. The elimination of copper ions was constant with increasing doses of bio-sorbent; however, a decrease close to 90% in the biosorption capacity was determined, when the dose of biosorbent increased from 1 to 10 g/L. The effect of the biosorption capacity increased proportionally with the initial concentration of copper ions; achieving biosorption of 8.3 and 12.9 mg of Cu+2/g of biosorbent, with walnut shell and olive pomace, respectively. Both biosorbent allowed copper ions removal close to 90%; however, to the olive pomace was not necessary a size reduction and had a higher copper ions biosorption capacity than the walnut shell.

Six fruit and vegetable peel beads for the simultaneous removal of heavy metals by biosorption

In this study, a comparison between the biosorption performance of six fruit and vegetable peels, namely kiwifruit (KP), apple, banana, cucumber, orange and potato immobilized on sodium alginate beads has been made. Inductively coupled plasma coupled with mass spectroscopy was used for measuring the concentration of metal ions in solution before and after biosorption. A range of kinetic models were also applied to the biosorption batch data. The results showed that biosorption percentage of the ions were different on the various beads. For example, the decreasing order of biosorption by one KP bead at equilibrium was Cd > Cu > Hg > Ni > Pb > Cr > As, with approximately 92%, 84%, 80%, 75%, 67%, 34%, and 17% simultaneous removal of ions, respectively. The fastest biosorption was seen with Cd and Pb, as both reached equilibrium by 24 h. Equilibrium time of all other ions occurred by 48 h. While all beads in their unmodified form were suitable for the removal of divalent cations, KP bead showed significantly higher removal of the anion hexavalent Cr. Biosorption of Cd, Hg and Ni was limited by both pseudo-first order and pseudo-second order reaction rates. For Cr and Cu, the reaction was controlled by film diffusion and pseudo-first order rates. At a higher solution concentration, the preference of ions biosorbed as well as their percentage removed changed. Overall, the results indicated that KP beads show promise as a cost-effective method for removing toxic ions by biosorption, especially hexavalent chromium from drinking water.

Olive mill wastewater: From a pollutant to green fuels, agricultural and water source and bio-fertilizer - Hydrothermal carbonization

Hydrothermal carbonization (HTC) is considered as a promising technique for wastes conversion into carbon rich materials for various energetic, environmental and agricultural applications. In this work, the HTC of olive mill wastewater (OMWW) was investigated at different temperatures (180-220 °C) and both, the solid (i.e., hydrochars) and the final process liquid derived from the thermal conversion process were deeply analyzed. Results showed that the solid yield was affected by the temperature, i.e., decrease from 57% to 25% for temperatures of 180 °C and 220 °C, respectively. Furthermore, the hydrochars presented an increasing fixed carbon percentage with the increase of the carbonization temperature, suggesting that decarboxylation is the main reaction driving the HTC process. The decrease in the O/C ratio promoted an increase of the high heating value (HHV) by 32% for hydrochar prepared at 220 °C. The process liquids were sampled and their organic contents were analyzed using GC-MS technique. Acids, alcohols, phenols and sugar derivatives were detected and their concentrations varied with carbonization temperatures. The assessment of the physico-chemical properties of the generated HTC by-products suggested the possible application of the hydrochars for energetic insights while the liquid fraction could be practical for in agricultural field.

Olive Mill Wastewater: From a Pollutant to Green Fuels, Agricultural Water Source, and Bio-Fertilizer. Part 2: Water Recovery

Water shortage is a very concerning issue in the Mediterranean region, menacing the viability of the agriculture sector and in some countries, population wellbeing. At the same time, liquid effluent volumes generated from agro-food industries in general and olive oil industry in particular, are quite huge. Thus, the main aim of this work is to suggest a sustainable solution for the management of olive mill wastewaters (OMWW) with possible reuse in irrigation. This work is a part of a series of papers valorizing all the outputs of a three-phase system of oil mills. It deals with recovery, by condensation, of water from both OMWW and OMWW-impregnated biomasses (sawdust and wood chips), during a convective drying operation (air velocity: 1 m/s and air temperature: 50 °C). The experimental results showed that the water yield recovery reaches about 95%. The condensate waters have low electrical conductivity and salinities but also acidic pH values and slightly high chemical oxygen demand (COD) values. However, they could be returned suitable for reuse in agriculture after additional low-cost treatment.