Synthesis of BaCO 3 particles tailored by carboxylated cellulose fibers

The present work deals with the use of carboxylated cellulose fibers, thereafter called Cellulose Nano Fibers (CNF), as eco-friendly materials and sustainable resources for remediation and valuation, of metal ions present in contaminated water. Barium divalent cation (Ba2+) is among the most common heavy metal pollutants found in water such as arsenic, cadmium, chromium, copper, nickel, lead and mercury. Thus, CNFs containing carboxylate groups were first prepared by the oxidation of the cellulose fibers using the NaOCl-NaBr-TEMPO system, and thereafter, they were used as adsorbent for Ba2+ ions removal from BaCl2 aqueous solutions. Such Ba2+ removal was evidenced by the decrease of both the CNF surface charge and the CNF absorbance, upon the addition of the metal divalent cation, BaCl2 to the CNF aqueous dispersions. It is shown that the interaction occurring between the fiber carboxylic groups and the positively charged metal ions, Ba2+, occurs via electrostatic interactions and leads to the CNFs –Ba2+ complex formation. In the second part of this work, we investigated the effect of the CNFs on the crystallogenesis of barium carbonate particles, BaCO3. Thus, the CNFs aqueous solution was first added to barium chloride BaCl2 solution, and the mixture was stirred for a period of time (complexation time), prior the addition of sodium carbonate (Na2CO3) solution. The precipitation of barium carbonate particles in the presence of CNFs occurred at ambient temperature, in a water-jacketed Pyrex glass vessel. Finally, the resulting Barium carbonate-CNFs composites were examined by various methods such as Scanning Electronic Microscopy (SEM), and X-ray Diffraction. From the SEM data, two BaCO3 morphologies were observed, dendritic and bent or rods particles, respectively, in the absence and in the presence of the CNFs

Mineralogical and Physico-Chemical Characterizations of Ferruginous Beidellite-Rich Clay from Agadir Basin (Morocco)

The mechanism of formation of detrital, beidellite-rich clay occurring in the Agadir basin (Morocco) is well documented, but its detailed characterization is incomplete which limits its application. The aim of the present study was to provide further details of the mineralogical and physico-chemical characteristics of this clay. Bulk raw clay and its Na+-saturated, <2 mm fraction were characterized using chemical, structural, and thermal techniques. Measurements of induced streaming potential (e.g. particle charge) and of specific surface area and porous volume are reported. The raw clay contained carbonate and quartz as associated minerals along with phyllosilicates (<2 mm particle size). X-ray diffraction and scanning electron microscopy analyses showed that the <2 mm fraction was dominated by a dioctahedral smectite. Because dehydroxylation of this mineral occurred at 510ºC, and because it re-expanded in ethylene glycol after Li+-saturation followed by heating at 240ºC for 24 h, the mineral was shown to be a beidellite rather than montmorillonite. This assertion was further supported by 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectra showing predominantly negative charges in the tetrahedral sheets due to notable Al-for-Si substitutions. The chemical composition of the <2 mm fraction showed an Fe2O3 content which was ~7.52 wt.% greater than those of other beidellite occurrences but not so much that it would be identified as a nontronite. The absence of stretching and bending absorption bands corresponding to characteristic (Fe2OH) units in mid-infrared spectra and their corresponding fundamental overtones or combination bands in near-infrared spectra supported this notion. The structural formula of the beidellite in the present study was determined to be (Si7.51Al0.49)(Al2.99Fe0.68Mg0.33) (Ca0.03Na0.54Mg0.11)O20(OH)4, having dioctahedral ferruginous characteristics with almost 60% of the negative charge found in tetrahedral sheets. The cation exchange capacity determined from the structural formula was ~108 meq/100 g. The specific surface area and total pore volume were ~82.2 m2/g and 0.136 cm3/g, respectively. Interestingly, a detrital rather than a hydrothermal-alteration origin, as reported for other beidellite occurrences, explains its natural abundance and emphasizes the great interest in it

Agglomeration of Silicon Dioxide Nanoscale Colloids in Chemical Mechanical Polishing Wastewater: Influence of pH and Coagulant Concentration

Chemical mechanical polishing (CMP) wastewater generated from semiconductor manufacturing industries is known to contain residual organic and inorganic contaminants, i.e. photoresists, acids, including silicon dioxide (SiO2), nanoparticles (NPs) and others. Nanoscale colloids in CMP wastewater have strong inclination to remain in the suspension, leading to high turbidity and chemical oxygen demand (COD). Although various types of pre-treatment have been implemented, these nanoparticles remain diffused in small clusters that pass through the treatment system. Therefore, it is crucial to select suitable pH and coagulant type in the coagulation treatment process. In this research zeta potential and dynamic light scattering measurements are applied as preliminary step aimed at determining optimum pH and coagulant dosage range based on the observation of inter particle-particle behavior in a CMP suspension. The first phase of the conducted study is to analyze nanoscale colloids in the CMP suspension in terms of zeta potential and z-average particle size as a function of pH within a range of 2 to 12. Two types of coagulants were investigated - polyaluminum chloride (PACl) and ferrous sulfate heptahydrate (FeSO4 center dot 7H(2)O). Similar pH analysis was conducted for the coagulants with the same pH range separately. The second phase of the study involved evaluating the interaction between nanoscale colloids and coagulants in the suspension. The dynamics of zeta potential and corresponding particle size were observed as a function of coagulant concentration. Results indicated that CMP wastewater is negatively charged, with average zeta potential of -59.8 mV and 149 d.nm at pH value of 8.7. The interaction between CMP wastewater and PACl showed that positively charged PACl rapidly adsorbed colloids in the wastewater, reducing the negative surface charge of nanoscale clusters. The interaction between CMP wastewater and FeSO4 center dot 7H(2)O showed that larger dosage is required to aggregate nanoscale clusters, due to its low positive value to counter negative charges of CMP wastewater

Ecailles de poissons : nouveau support de biomasse dans les bioréacteurs a lit mobile pour le traitement des effluents des laiteries

Cette étude porte sur le traitement par voie biologique de la charge polluante organique des effluents des laiteries. Un déchet de la pêche, des écailles de poissons de l’espèce Diplodus sargus cadenati (Sar Gros, E.SG) a été testé en tant que garnissage support de biofilm dans un bioréacteur à lit mobile, dans le but d’améliorer les performances d’épuration. Les résultats obtenus sur certains paramètres de la dépollution (pH, DCO, MES, azote total) sont prometteurs. La quantité d’écailles nécessaire a été optimisée pour des raisons économiques et écologiques. This study focuses on the biological treatment of organic pollution load of effluents dairies. It proposes a new method. i.e. The use of fish scales Diplodus sargus species, as a solid support for colonization of suspended biomass in the bioreactor moving bed in order to improve the properties and quality of clearance. The results of monitoring the parameters of pollution control (pH, COD, MS, total nitrogen) are promising. Finally the amount of scales necessary has been optimized for economic and ecological reasons

Agglomeration of Silicon Dioxide Nanoscale Colloids in Chemical Mechanical Polishing Wastewater: Influence of pH and Coagulant Concentration

Chemical mechanical polishing (CMP) wastewater generated from semiconductor manufacturing industries is known to contain residual organic and inorganic contaminants, i.e. photoresists, acids, including silicon dioxide (SiO2), nanoparticles (NPs) and others. Nanoscale colloids in CMP wastewater have strong inclination to remain in the suspension, leading to high turbidity and chemical oxygen demand (COD). Although various types of pre-treatment have been implemented, these nanoparticles remain diffused in small clusters that pass through the treatment system. Therefore, it is crucial to select suitable pH and coagulant type in the coagulation treatment process. In this research zeta potential and dynamic light scattering measurements are applied as preliminary step aimed at determining optimum pH and coagulant dosage range based on the observation of inter particle-particle behavior in a CMP suspension. The first phase of the conducted study is to analyze nanoscale colloids in the CMP suspension in terms of zeta potential and z-average particle size as a function of pH within a range of 2 to 12. Two types of coagulants were investigated - polyaluminum chloride (PACl) and ferrous sulfate heptahydrate (FeSO4 center dot 7H(2)O). Similar pH analysis was conducted for the coagulants with the same pH range separately. The second phase of the study involved evaluating the interaction between nanoscale colloids and coagulants in the suspension. The dynamics of zeta potential and corresponding particle size were observed as a function of coagulant concentration. Results indicated that CMP wastewater is negatively charged, with average zeta potential of -59.8 mV and 149 d.nm at pH value of 8.7. The interaction between CMP wastewater and PACl showed that positively charged PACl rapidly adsorbed colloids in the wastewater, reducing the negative surface charge of nanoscale clusters. The interaction between CMP wastewater and FeSO4 center dot 7H(2)O showed that larger dosage is required to aggregate nanoscale clusters, due to its low positive value to counter negative charges of CMP wastewater