Mohamed Chaker Ncibi

Optimized removal of antibiotic drugs from aqueous solutions using single, double and multi-walled carbon nanotubes

In this study, experiments were carried out to investigate the use of as-synthesized single-walled (SWCNT), double-walled (DWCNT) and multi-walled carbon nanotubes (MWCNT) agglomerates for the removal of two antibiotics, Oxytetracycline (OXY) and Ciprofloxacin (CIP) from aqueous solution. The variations of key operating parameters on the removal process were assessed in order to find out the optimum conditions. It includes exposure time, solution pH, temperature, ultrasound assistance and desorption assays. The experimental results revealed that a moderate increase in adsorption was registered between pH 3 and 7 for both antibiotics. The application of ultrasound helped enhancing the removal capacities of OXY for all tested CNTs. For the case of MWCNTs, 1h of ultrasonication increased the adsorption capacity by 44.6%. As for CIP, the ultrasonic treatment did not enhance the overall adsorption, especially for the case of DWCNTS. The Brouers-Sotolongo equation was the best fitting isotherm model. The highest removal capacities were registered using SWCNTS for both antibiotics (724 mg/g for CIP and 554 mg/g for OXY). In addition, ethanol was the solvent that induced the highest desorption percent for the case of CIP (52% for MWCNTs). However, the desorption of OXY was negligible for all solvents (maximum 3.3% for DWCNTs using ethanol).

Studies on the Biosorption of Textile Dyes from Aqueous Solutions Using Posidonia Oceanica (L.) Leaf Sheath Fibres

The adsorption of two textile dyes onto a low-cost and unexploited marine biomass, Posidonia oceanica (L.), was investigated in batch mode. The biosorption process was studied as a function of contact time, initial pH and temperature. The highest dye adsorption capacities attained at 30°C were 3.081 mg/g at pH 2 for the Direct dye and 4.252 mg/g at pH 5 for the Reactive dye. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used to determine the parameters of the equilibrium data and, under the operating conditions studied, the best fit to the experimental curves was obtained using the Freundlich model. The thermodynamic constants of the adsorption process (i.e. ΔG0, ΔH0 and ΔS9) were evaluated as −6.36 kJ/mol, 57.80 kJ/mol and −103.45 J/(mol K), respectively, for the Direct dye and as −3.22 kJ/mol, 84.10 kJ/mol and −225.55 J/(mol K), respectively, for the Reactive dye. Consequently, the adsorption of dyes onto P. oceanica biomass was favourable, endothermic and spontaneous.

Biosorptive uptake of methylene blue using Mediterranean green alga Enteromorpha spp.

Batch biosorption experiments were carried out for the removal of methylene blue, a basic dye, from aqueous solution using raw and dried Enteromorpha spp., Mediterranean green alga. A series of assays were undertaken to assess the effect of the system variables, i.e. contact time, solution pH and sorbent amount. The results had showed that sorption capacity was optimal using 6-10 solution pH range (i.e. maximum adsorption capacity of 274 mg/g). The minimum sorbent concentration experimentally found to be sufficient to reach the total removal of the dye molecules from the aqueous solution was 5 g/L. Besides, equilibrium data were fitted using five linearisable isotherm models. The related results showed that the experimental data were very well represented by the Langmuir model for the linear regression analysis and both the Langmuir and Redlich-Peterson isotherm models for the non-linear analysis. In both cases, such modelling behaviour confirms the monolayer coverage of methylene blue molecules onto energetically homogenous Enteromopha surface. In addition, an exhaustive comparative study was done to situate this marine biomass among other proposed sorbents.

Removal of natural organic matter in drinking water treatment by coagulation: A comprehensive review

Natural organic matter (NOM) is a complex matrix of organic substances produced in (or channeled to) aquatic ecosystems via various biological, geological and hydrological cycles. Such variability is posing a serious challenge to most water treatment technologies, especially the ones designed to treat drinking water supplies. Lately, in addition to the fluctuating composition of NOM, a substantial increase of its concentration in fresh waters, and also municipal wastewater effluents, has been reported worldwide, which justifies the urgent need to develop highly efficient and versatile water treatment processes. Coagulation is among the most applied processes for water and wastewater treatment. The application of coagulation to remove NOM from drinking water supplies has received a great deal of attention from researchers around the world because it was efficient and helped avoiding the formation of disinfection by products (DBPs). Nonetheless, with the increased fluctuation of NOM in water (concentration and composition), the efficiency of conventional coagulation was substantially reduced, hence the need to develop enhanced coagulation processes by optimizing the operating conditions (mainly the amount coagulants and pH), developing more efficient inorganic or organic coagulants, as well as coupling coagulation with other water treatment technologies. In the present review, recent research studies dealing with the application of coagulation for NOM removal from drinking water supplies are presented and compared. In addition, integration schemes combining coagulation and other water treatment processes are presented, including membrane filtration, oxidation, adsorption and others processes.

As-synthesized multi-walled carbon nanotubes for the removal of ionic and non-ionic surfactants

This research deals with the application of untreated multi-walled carbon nanotubes (MWCNT) in their agglomerates form for the removal of non-ionic (TX-100), cationic (CTAB) and anionic (SDBS) surfactants from aqueous media. In order to optimize the removal process, the influence of several key parameters was investigated including contact time under different solid/liquid ratios, initial solution pH, temperature, along with ultrasonication assistance and desorption assays. Experimentations revealed that pH variation enhanced the removal capacities at optimum values of 6, 2 and 8 for TX-100, SDBS and CTAB, respectively, and that hydrophobic interaction is a major adsorption factor, especially for non-ionic surfactant with possible electrostatic interactions occurring for the ionic ones. As well, removal efficiencies peaked for an optimum temperature range between 35 and 45 °C. As for the ultrasonication assistance, it enhanced the overall removal capacities, especially that of the ionic surfactant, with an enhancement of 52% for the case of SDBS after 1h of treatment. The modeling results revealed that the pseudo-second order model provided the best correlation of the dynamic data and that the process was controlled by intraparticle diffusion phenomena. At equilibrium, and under optimized experimental conditions, untreated MWCNTs showed promising removal capacities with 359, 312 and 156 mg/g for TX-100, SDBS and CTAB, respectively.

Assessing membrane fouling and the performance of pilot-scale membrane bioreactor (MBR) to treat real municipal wastewater during winter season in Nordic regions

In this study, the performance of a pilot-scale membrane bioreactor (MBR) to treat real municipal wastewater was assessed at low temperatures (7 to 20°C) in Nordic regions. First, the effect of low temperatures on membrane fouling was evaluated by monitoring trans-membrane pressure. A significant membrane fouling was observed when the sludge temperature inside the MBR unit was below 10°C with a 75% permeability drop, thus indicating high deterioration of the membrane performance at low temperatures. Moreover, increasing values of sludge volume index (SVI) during low temperatures showed high deterioration of sludge settleability. As for the pollution removal, MBR achieved high performances primarily for pathogens and emerging micropollutants. The average log reductions of 1.82, 3.02, and 1.94 log units were achieved for norovirus GI, norovirus GII, and adenoviruses, respectively. Among the four trace organic compounds (TrOCs), the average removal efficiencies of bisoprolol, diclofenac and bisphenol A were 65%, 38%, and >97%, respectively. However, carbamazepine was not efficiently removed (-89% to 28%). Regarding trace metals, an average removal of >80% was achieved for Cd, Pb, and V. For the rest of the metals, the removal capacities were between 30 and 60%.

Biosorption of metal dye from aqueous solution onto Agave americana (L.) fibres

In this research, a new low cost and abundant biosorbent; Agave americna (L.) fibres has been investigated in order to remove metal dye (Alpacide yellow) from aqueous solutions. In order to optimize the biosorption process, the effect of pH, temperature, contact time and initial solution concentration was investigated in batch system. The results indicated that acidic pH=2 was favourable for metal dye removal. The increase of temperature increases the velocity of the biosorption reaction. The biosorption kinetics of alpacide yellow were closer to the pseudo-second order than to the first order model for all concentrations and temperature. The calculated thermodynamic parameters such as dGG∘, dGH∘ and dGS∘ indicated a spontaneous and endothermic biosorption process of metal dye onto Agave americana fibres. The equilibrium data were analysed using the Langmuir and Freundlich isotherms and showed a good fit with Langmuir model at lower temperatures and with Freundlich model at 50 °C.

Advanced oxidation processes for the removal of natural organic matter from drinking water sources: A comprehensive review

Natural organic matter (NOM), a key component in aquatic environments, is a complex matrix of organic substances characterized by its fluctuating amounts in water and variable molecular and chemical properties, leading to various interaction schemes with the biogeosphere and hydrologic cycle. These factors, along with the increasing amounts of NOM in surface and ground waters, make the effort of removing naturally-occurring organics from drinking water supplies, and also from municipal wastewater effluents, a challenging task requiring the development of highly efficient and versatile water treatment technologies. Advanced oxidation processes (AOPs) received an increasing amount of attention from researchers around the world, especially during the last decade. The related processes were frequently reported to be among the most suitable water treatment technologies to remove NOM from drinking water supplies and mitigate the formation of disinfection by products (DBPs). Thus, the present work overviews recent research and development studies conducted on the application of AOPs to degrade NOM including UV and/or ozone-based applications, different Fenton processes and various heterogeneous catalytic and photocatalytic oxidative processes. Other non-conventional AOPs such as ultrasonication, ionizing radiation and plasma technologies were also reported. Furthermore, since AOPs are unlikely to achieve complete oxidation of NOM, integration schemes with other water treatment technologies were presented including membrane filtration, adsorption and others processes.

Biomass for sustainable applications : pollution remediation and energy

Part A: Energetic Application Bacteria for bioenergy: Microbial Fuel Cells Bacteria for bioenergy: Biomethanisation Plantae and marine biomass for biofuels Plantae and marine biomass derived porous materials for electrochemical energy storage Biomass-based renewable energy systems Part B : Pollution Remediation Plantae and marine biomass for water treatment Plantae and marine biomass for soil treatment: Phytoremediation Microorganisms for water treatment Microorganisms for soil treatment Biological waste gas treatment

Occurrence, identification and removal of microplastic particles and fibers in conventional activated sludge process and advanced MBR technology

Wastewater treatment plants (WWTPs) are acting as routes of microplastics (MPs) to the environment, hence the urgent need to examine MPs in wastewaters and different types of sludge through sampling campaigns covering extended periods of time. In this study, the efficiency of a municipal WWTP to remove MPs from wastewater was studied by collecting wastewater and sludge samples once in every two weeks during a 3-month sampling campaign. The WWTP was operated based on the conventional activated sludge (CAS) process and a pilot-scale membrane bioreactor (MBR). The microplastic particles and fibers from both water and sludge samples were identified by using an optical microscope, Fourier Transform Infrared (FTIR) microscope and Raman microscope. Overall, the retention capacity of microplastics in the studied WWTP was found to be 98.3%. Most of the MP fraction was removed before the activated sludge process. The efficiency of an advanced membrane bioreactor (MBR) technology was also examined. The main related finding is that MBR permeate contained 0.4 MP/L in comparison with the final effluent of the CAS process (1.0 MP/L). According to this study, both microplastic fibers and particles are discharged from the WWTP to the aquatic environment.