Activated Carbon Prepared from Waste Coffee Grounds: Characterization and Adsorption Properties of Dyes.

Spent coffee grounds (SCGs) have great potential as a useful, value-added biological material. In this context, activated carbon (AC) was prepared from SCGs by an activation process using H3PO4 at 600 °C in the air and used as an adsorbent for the azo dye AO7, a model molecule for dye colorants found in textile industry effluents. X-ray diffraction, SEM and BET revealed that the AC was predominantly amorphous, consisting of a powder of 20-100 µm particles with mesopores averaging 5.5 nm in pore size. Adsorption kinetics followed a pseudo-second-order law, while the Langmuir model best fitted the experimental isotherm data (maximum capacity of 119.5 mg AO7 per AC g). The thermodynamic parameters revealed that adsorption was endothermic and spontaneous. All the characterizations indicated that adsorption occurred by physisorption via mainly π-π interactions. The best experimental removal efficiency optimized by means of a Box-Behnken design and response surface methodology was 98% for an initial AO7 concentration of 20 mg·L-1 at pH 7.5 with a dose of 0.285 g·L-1 of AC and a contact time of 40 min. These results clearly show that activated carbon prepared from SCGs can be a useful material for efficiently removing organic matter from aqueous solutions.

Preparation and Characterization of New and Low-Cost Ceramic Flat Membranes Based on Zeolite-Clay for the Removal of Indigo Blue Dye Molecules.

Composite flat membranes were prepared using a dry uniaxial pressing process. The effect of the sintering temperature (850-950 °C) and smectite proportion (10-50 wt.%) on membrane properties, such as microstructure, mechanical strength, water permeability, and treatment performances, was explored. It was observed that increasing the sintering temperature and adding higher amounts of smectite increased the mechanical strength and shrinkage. Therefore, 850 °C was chosen as the optimum sintering temperature because the composite membranes had a very low shrinkage that did not exceed 5% with high mechanical strength, above 23 MPa. The study of smectite addition (10-50 wt.%) showed that the pore size and water permeability were significantly reduced from 0.98 to 0.75 µm and from 623 to 371 L·h-1·m-2·bar-1, respectively. Furthermore, the application of the used membranes in the treatment of indigo blue (IB) solutions exhibited an almost total turbidity removal. While the removal of color and COD decreased from 95% to 76%, respectively, they decreased from 95% to 52% when the amount of smectite increased. To verify the treated water's low toxicity, a germination test was performed. It has been shown that the total germination of linseed grains irrigated by MS10-Z90 membrane permeate was identical to that irrigated with distilled water. Finally, based on its promising properties, its excellent separation efficiency, and its low energy consumption, the MS10-Z90 (10 wt.% smectite and 90 wt.% zeolite) sintered at 850 °C could be recommended for the treatment of colored industrial wastewater.

Development of Ultrafiltration Kaolin Membranes over Sand and Zeolite Supports for the Treatment of Electroplating Wastewater.

A high cost of high-purity materials is one of the major factors that limit the application of ceramic membranes. Consequently, the focus was shifted to using natural and abundant low-cost materials such as zeolite, clay, sand, etc. as alternatives to well-known pure metallic oxides, such as alumina, silica, zirconia and titania, which are usually used for ceramic membrane fabrication. As a contribution to this area, the development and characterization of new low-cost ultrafiltration (UF) membranes made from natural Tunisian kaolin are presented in this work. The asymmetric ceramic membranes were developed via layer-by-layer and slip-casting methods by direct coating on tubular supports previously prepared from sand and zeolite via the extrusion process. Referring to the results, it was found that the UF kaolin top layer is homogenous and exhibits good adhesion to different supports. In addition, the kaolin/sand and kaolin/zeolite membranes present an average pore diameter in the range of 4-17 nm and 28 nm, and water permeability of 491 L/h·m2·bar and 182 L/h·m2·bar, respectively. Both membranes were evaluated in their treatment of electroplating wastewater. This was done by removing oil and heavy metals using a homemade crossflow UF pilot plant operated at a temperature of 60 °C to reduce the viscosity of the effluent, and the transmembrane pressure (TMP) of 1 and 3 bar for kaolin/sand and kaolin/zeolite, respectively. Under these conditions, our membranes exhibit high permeability in the range of 306-336 L/h·m2·bar, an almost total oil and lead retention, a retention up to 96% for chemical oxygen demand (COD), 96% for copper and 94% for zinc. The overall data suggest that the developed kaolin membranes have the potential for remediation of oily industrial effluents contaminated by oil and heavy metals.

Treatment of Tuna Cooking Juice via Ceramic Ultrafiltration Membrane: Optimization Using Response Surface Methodology.

In the present work, optimized ultrafiltration conditions, using a ceramic multi tubular titania membrane (150 KDa), were investigated for the treatment of tuna cooking juice, for water reuse in the industrial process. The interactive effects of the volume concentrating factor (VCF) (1.03-4.25), feed temperature (T) (20-60 °C), and applied transmembrane pressure (ΔP) (2-5 bar) on protein removal (R protein) and permeate flux (J) were determined. A Box-Behnken experimental design (BBD) with the response surface methodology (RSM) was used for statistical analysis, modeling, and optimization of the operating conditions. The analysis of variance (ANOVA) results proved that the protein removal and permeate flux were significant and represented good correlation coefficients of 0.9859 and 0.9294, respectively. Mathematical modeling showed that the best conditions were VCF = 1.5 and a feed temperature of 60 °C, under a transmembrane pressure of 5 bar. The fouling mechanism was checked by applying a polarization concentration model. Determination of the gel concentration confirmed the results found in the mass balance calculation and proved that the VCF must not exceed 1.5. The membrane regeneration efficiency was proven by determining the water permeability after the chemical cleaning process.

Synthesis and Evaluation of Asymmetric Mesoporous PTFE/Clay Composite Membranes for Textile Wastewater Treatment.

Asymmetric mesoporous composite PTFE membranes wit 40, 50, and 85 wt.% of a clay (kaolin) were fabricated and characterized using a scanning electron microscope equipped with EDX for morphology and elemental analysis. The surface chemistry of the membranes was checked using Fourier transform infrared spectroscopy. The effect of incorporating the clay on the hydrophilicity, permeability, morphology, and antifouling properties of the fabricated membranes was investigated. It was observed that incorporating kaolin particles improved the mechanical properties but decreased the contact angle of the membranes, thereby resulting in an improvement in the membrane permeability. The performance of the three composite UF membranes was evaluated through the treatment of a real textile effluent sample containing indigo dye. The results confirmed that these membranes are effective in the removal of COD, color, and turbidity. Indeed, at a transmembrane pressure of 2.5 bar, almost total removal of the turbidity, COD removal > 85%, and color removal > 97% were attained. Furthermore, membrane A85 (with 85% clay) showed the best performance, with a water flux of 659.1 L·h-1·m-2·bar-1. This study highlights the potential of incorporating low-cost clay material for the enhancement of the performance of mixed organic/inorganic matrix membranes, which can be applied to textile wastewater treatment.

Removal of fluoride ions (F-) from aqueous solutions using modified Turkish zeolite with quaternary ammonium.

The natural Turkish zeolite has been modified with hexadecyltrimethylammonium bromide (CTAB) for the elimination of fluoride (F-) from aqueous solutions. The parent natural zeolite (NZ) and modified zeolite (MZ) have been characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), zeta potentials and Brunauer-Emmett-Teller (BET) method. The effect of pH, adsorbent dose, contact time, initial concentration and temperature on adsorption of fluoride ions onto modified zeolite (MZ) has been determined in batch experiments. Fluoride concentration can be reduced to 1.5 mg/L under the optimum condition (pH = 5, adsorbent dose = 20 mg/L, contact time = 60 min and T = 293 K) when initial fluoride concentration of 10 mg/L is employed. The fluoride adsorption on MZ has been described by the Langmuir isotherm and the maximum fluoride adsorption capacity was found as 2.994 mg/g. Kinetics data were best described by the pseudo-second-order model. The thermodynamic studies proved that the adsorption was exothermic and spontaneous.

Treatment of textile wastewater using monolayered ultrafiltation ceramic membrane fabricated from natural kaolin clay.

Fabrication, characterization and application of ceramic membrane developed from Tunisian natural kaolin clay for textile wastewater treatment are presented in this study. The morphology and properties of the resulting membrane sintered at 1000°C for 3 h were then determined by Scanning Electron Microscopy (SEM), mechanical and chemical resistance and water permeability. Separation performance of the membrane was evaluated during the treatment of textile wastewater. SEM images reveal the homogeneous surface of the membrane. The membrane displayed good chemical and mechanical resistances as well. Its permeability was of 21.2 L.h -1.m-2.bar-1, indicating that separation performance could occur in the domain of Ultrafiltration (UF). Performances of the membrane during the treatment of raw and biologically pretreated textile effluents are promising in terms of the removal of colour (99% for the raw effluent and 100% for the biologically pretreated effluent), chemical oxygen demand (COD) (80% for the raw effluent and 93% for the biologically pretreated effluent) and turbidity (98% for the raw effluent and 100% for the biologically pretreated effluent).

Valorisation of tuna processing waste biomass: isolation, purification and characterisation of four novel antioxidant peptides from tuna by-product hydrolysate.

Tuna protein hydrolysate (TPH) was prepared by hydrolysis with Prolyve BS and fractionated by membranes process. The antioxidant activities of recovered peptide fractions were evaluated. Four novel antioxidant peptides that were isolated from nanofiltration retentate exhibited the highest antioxidant activity, using gel chromatography and reversed phase high-performance liquid chromatography. The amino acid sequences of isolated peptides were identified as Tyr-Glu-Asn-Gly-Gly (P2), Glu-Gly-Tyr-Pro-Trp-Asn (P4), Tyr-Ile-Val-Tyr-Pro-Gly (P7) and Trp-Gly-Asp-Ala-Gly-Gly-Tyr-Tyr (P8) with molecular weights of 538.46, 764.75, 710.78 and 887.85 Da, respectively. P2, P4, P7 and P8 exhibited good scavenging activities on hydroxyl radical (IC50 0.41, 0.327, 0.17 and 0.042 mg/ml), DPPH radical (IC50 0.666, 0.326, 0.451 and 0.377 mg/ml) and superoxide radical (IC50 0.536, 0.307, 0.357 and 0.115 mg/ml). P7 was effective against lipid peroxidation in the model system. The isolated peptides might be useful used as natural food additive in food industry and formulation of nutritional products.

Valorisation of tuna processing waste biomass for recovery of functional and antioxidant peptides using enzymatic hydrolysis and membrane fractionation process.

The enzymatic hydrolysis using Prolyve BS coupled to membrane process (Ultrafiltration (UF) and nanofiltration (NF)) is a means of biotransformation of tuna protein waste to Tuna protein hydrolysate (TPH) with higher added values. This method could be an effective solution for the production of bioactive compounds used in various biotechnological applications and minimizing the pollution problems generated by the seafood processing industries. The amino acid composition, functional and antioxidant properties of produced TPH were evaluated. The results show that the glutamic acid, aspartic acid, glycine, alaline, valine and leucine were the major amino acids detected in the TPH profile. After membrane fractionation process, those major amino acids were concentrated in the NF retentate (NFR). The NFR and NF permeate (NFP) have a higher protein solubility (>95 %) when compared to TPH (80 %). Higher oil and water binding capacity were observed in TPH and higher emulsifying and foam stability was found in UF retentate. The NFP showed the highest DPPH radical scavenging activity (65 %). The NFR contained antioxidant amino acid (30.3 %) showed the highest superoxide radical and reducing power activities. The TPH showed the highest iron chelating activity (75 %) compared to other peptide fractions. The effect of the membrane fractionation on the molecular weight distribution of the peptide and their bioactivities was underlined. We concluded that the TPH is a valuable source of bioactive peptides and their peptide fractions may serve as useful ingredients for application in food industry and formulation of nutritional products.

Effects of dietary extra virgin olive oil and its fractions on antioxidant status and DNA damage in the heart of rats co-exposed to aluminum and acrylamide.

Oxidative stress generated by an excessive production of free radicals has been linked to the development of several health problems such as cardiovascular diseases. We investigated the protective efficacy of Extra Virgin Olive Oil (EVOO) and its lipophilic fraction (OOLF) and hydrophilic fraction (OOHF) against the cardiotoxicity and DNA damage induced by co-exposure to aluminum (AlCl3) and acrylamide (ACR). Rats were divided into eight groups of six each: controls, AlCl3 (50 mg per kg body weight) administered via drinking water and ACR (20 mg per kg body weight) given by gavage, combined group plus EVOO (300 µl); combined group plus the hydrophilic fraction (1 ml); combined group plus the lipophilic fraction (300 µl); extra virgin olive oil (EVOO) and its fractions were administered daily by gavage for 21 days. Three other groups, considered as positive controls, received either EVOO, OOLF or OOLH. Exposure of rats to both AlCl3 and ACR provoked oxidative stress objectified by an increase in MDA, AOPP and a decrease in GSH, NPSH and vitamin C levels. The activities of CAT, GPx and SOD were also decreased. EVOO and its OOLF fraction exhibited a pronounced enhancement of antioxidant status while a partial recovery in the antioxidant status was obtained with the OOHF fraction. Plasma LDH and CK activities, TC, LDL-C levels, TC/HDL-C and LDL-C/HDL-C ratios were increased, while HDL-C and TG decreased in rats treated with both AlCl3 and ACR. Co-administration of EVOO, OOLF or OOHF to treated rats restored cardiac biomarkers and lipid profile to near-normal values. Histological studies and DNA damage confirmed the biochemical parameters and the beneficial role of EVOO and its two fractions. Our results suggest that extra virgin olive oil and its two fractions can decrease the frequency of cardiac complications and genotoxicity.