Hatem Dhaouadi

Nonlinear modelisation of heavy metal removal from aqueous solution using Ulva lactuca algae

After extensive analysis, Ulva lactuca dried algae, collected from the Monastir coastal zone, was proven to be successful as an adsorbent for the removal of certain inorganic pollutants. The main objective of this study was the nonlinear modeling of heavy metal removal from an aqueous solution, using a freely available and well analyzed biomaterial, as well as the evaluation of its efficacy on various metal ion sorptions. Although relatively low specific surface area, compared to more conventional adsorbents, the selected biomaterial displays very interesting retention capacities when used with aqueous inorganic pollutants. The pseudo, first and second-order kinetic models were used to investigate the kinetic retention mechanism. Assuming the nonlinear form, the results indicate that the retention mechanism is diffusion controlled. Concerning the heavy metal uptake capacity, it was found that the selected biomaterial has a retention capacity of 67 mg g(-1) of Ni(II), 112 mg g(-1) of Cu(II), 127 mg g(-1) of Cd(II) and 230 mg g(-1) of Pb(II).

Microalgae from domestic wastewater facility’s high rate algal pond: Lipids extraction, characterization and biodiesel production

In this study, the harvesting of a biomass from a high rate algal pond (HRAP) of a real-scale domestic wastewater treatment facility and its potential as a biomaterial for the production of biodiesel were investigated. Increasing the medium pH to 12 induced high flocculation efficiency of up to 96% of the biomass through both sweep flocculation and charge neutralization. Lipids extracted by ultrasounds from this biomass contained around 70% of fatty acids, with palmitic and stearic acids being the most abundant. The extract obtained by supercritical CO2 contained 86% of fatty acids. Both conventional solvents extracts contained only around 10% of unsaturated fats, whereas supercritical CO2 extract contained more than 40% of unsaturated fatty acids. This same biomass was also subject to direct extractive-transesterification in a microwave reactor to produce fatty acid methyl esters, also known as, raw biodiesel.

New bioactive labdane diterpenoids from Marrubium aschersonii

Abstract A phytochemical investigation of the ethanol extract of Marrubium aschersonii Magnus (Lamiaceae) collected from Tunisia led to the isolation and identification of two new labdane diterpenoids, marrubaschs A (1) and B (2), along with two known compounds (3 and 4). Their structures were elucidated by spectroscopic methods including HRESIMS and NMR techniques. All compounds were evaluated for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide in RAW 264.7 macrophage cells. Compound 2 exhibited weak inhibition of NO production with an IC50 value of 35 ± 1.0 μM.

CFD Comparative Investigation of the Performances of Reverse Flow and Uni-Flow Hydrocyclones in the Enrichment of the Phosphate Pulp

This paper presents a CFD comparative investigation of two types of hydrocyclone: uni-flow and reverse flow hydrocyclones. The study is conducted by means of a Reynolds Averaged Navier-Stockes (RANS) simulation using the finite volume code Fluent. The fluid flow is described by the use of the Reynolds Stress Model, while the determination of particles flow and the air core formation are modeled by the mean of two multiphase models which are respectively the Stochastic Lagrangian model (DPM) and the Volume of Fluid Model (VOF). The flow features are examined in terms of pressure drop and separation efficiency in order to contribute to better performance. The validity of the proposed approach is verified by the good agreement between the predicted and the measured results which are given by the Company of Phosphate of Gafsa (CPG-Tunisia). This study proves that uniflow hydrocyclone is more energy efficient because of its lower pressure drop and its higher removal efficiency for small particles from their carrying fluid.

A TRNSYS Dynamic Simulation Model for Photovoltaic System Powering a Reverse Osmosis Desalination Unit with Solar Energy

This paper presents a Photovoltaic (PV) simulation system powering a reverse osmosis (RO) desalination unit with no energy recovery device (ERD). The simulation is carried out using commercial software, Transient System Simulation (TRNSYS®). The PV system consists on solar panels (Siemens SM55) with rated power of 55 W, connected to a storage battery via DC-DC charge controller. The load of this system is a pump, which provides the RO system with feed water. The RO unit is composed of one Filmtec spiral wound membrane. Simulation results for fresh water production showed that with a continuous feed of 1.5 m3h-1, a total capacity production of 110 m3 per year can be achieved. The effect of the main parameters in desalinated water production capacity showed that with the increase of the raw water feed flow and the PV surface, the monthly fresh water production increases. They also showed that with the increase of raw water salinity, the fresh water production decreases. This work is validated with literature experimental results.

Fatty acids from high rate algal pond’s microalgal biomass and osmotic stress effects

The extraction of oil from a wild microalgae biomass collected from a domestic wastewater treatment facilitys high rate algal pond (HRAP) was investigated. An experiment plan was used to determine the most efficient extraction method, the optimal temperature, time and solvent system based on total lipids yield. Microwave-assisted extraction was the most efficient method whether in n-hexane or in a mixture of chloroform/methanol compared to Soxhlet, homogenization, and ultrasounds assisted extractions. This same wild biomass was cultivated in a photobioreactor (PBR) and the effect of osmotic stress was studied. The lipids extraction yield after 3days of stress increased by more than four folds without any significant loss of biomass, however, the quality of extracted total lipids in terms of saturated, monounsaturated and polyunsaturated fatty acids was not affected by salinity change in the culture medium.

Sorption of paracetamol onto biomaterials

Pharmaceutical residues released into the environment are posing more and more public health problems. It is worthwhile to study the retention of pharmaceuticals residues by adsorption on solid supports. Batch sorption experiments are intended to identify the adsorption isotherms of the pharmaceutically active ingredient on the biomaterials. The results obtained in this study have shown that the retention possibilities of these compounds by bio-adsorbents (clay and sand) are not significant. The negligible sorption for these media is explained by the low hydrophobicity of paracetamol (Log K(ow) = 0.46). The retention of paracetamol on the dehydrated sewage sludge and on Posidonia oceanica showed a relatively significant adsorption with a maximal quantity of 0.956 mg g(-1) and 1.638 mg g(-1) for the dehydrate sludge and P. oceanica, respectively. On the other hand, the study of paracetamol retention on the powdered activated carbon showed a high adsorption capacity of about 515.27 mg g(-1). Isotherm data show a good fit with Langmuirs model. An infrared analysis is carried out. It shows identical bands before and after adsorption, with some modifications.