No abstract

In the present study, an intensified approach for the synthesis of starch nanoparticles (SNPs) was demonstrated by using ultrasound-assisted acid hydrolysis method. The conventional acid hydrolysis for the synthesis of SNPs was intensified using ultrasound. The overall time required to convert starch granules to SNPs in the conventional acid hydrolysis method (48 h) was significantly reduced to 45 min by simultaneous acid hydrolysis and ultrasound irradiation. The acid concentration was found to be an important parameter for obtaining the desired size and morphology of the synthesized SNPs. The variation in the surface charges associated with the SNPs was confirmed through measuring their zeta potential. These potential charges on the surface of SNPs induce crystal growth among the synthesized nanoparticles. The irregular crystal morphology at higher acid concentration clearly shows SNPs' attachment with each other by coalescence. The higher crystallinity for SNPs was observed at low acid concentration; however, the lower acid concentration (0.5 M) leads to the smaller particle size of SNPs from 40 to 60 nm, with the overall yield of 23%. The proposed ultrasound method is more efficient and reproducible for the synthesis of SNPs for various applications.

La présente étude porte sur le traitement physico-chimique d'un effluent industriel chargé d'encre de seiche issu de l'industrie de conditionnement des produits de la pêche. Différentes combinaisons de coagulant -floculant ont été étudiées. Le sulfate d'aluminium (SA), divers polyélectrolytes et certains adjuvants pulvérulents ont été utilisés. L'efficacité du traitement par coagulation-floculation a été analysée en suivant l'évolution de la turbidité et de la DCO résiduelle du surnageant.Les résultats de cette étude ont révélé qu'à pH 6-7, l'addition de SA à une concentration supérieure à 1000 mg.l-1 entraîne la coagulation des particules d'encre de seiche. L'addition d'un polyélectrolyte en association avec le SA permet de réduire la concentration requise en SA à environ 300 mg.l-1, tout en améliorant l'efficacité du processus de coagulation-floculation. Le recours à un adjuvant pulvérulent en combinaison avec le SA et un polyélectrolyte accroît notablement les performances du traitement et permet d'obtenir un effluent ayant une turbidité résiduelle de 7 NTU.The aim of this work was to compare the efficiency of a coagulation-flocculation process using different systems individually or in combination. The waste water used was an industrial cuttlefish effluent principally composed of colloidal particles from the cuttlefish. The initial turbidity and chemical oxygen demand were approximately 700 NTU and 22,000 mg×L-1 respectively. Two parameters were used to assess the process efficiency: the residual turbidity and the chemical oxygen demand (COD) of the supernatant.Three systems were investigated: aluminium sulphate (SA), polyelectrolytes and a ternary combination of SA-polyelectrolyte and colloidal microparticle adjuvant. Results demonstrated that at pH 6-7, SA caused some coagulation of the suspension, but the dosage required (about 1000 mg×L-1) far exceeded those conventionally used in water treatment. As a consequence, an appreciable amount of SA, which was above the authorised limits, remained in the supernatant. Indeed, adsorption isotherm measurements revealed that at pH 6.5-7 the residual proportion of SA attained was about 20%. The addition of polyelectrolytes in combination with SA allowed reduction of the SA dosage to 150 mg×L-1. Amongst the polymers tested, the cationic polymer was the most efficient. The ability to bring about flocculation was positively related to the molecular weight, which is in agreement with a bridging flocculation mechanism. Starch, a natural, low-cost polymer was also an efficient flocculent even though it is a non-charged polymer. The ability of starch to bring about a flocculation action was explained by its relatively low solubility, which leads to some aggregation of macromolecular chains that act as anchoring sites for the coagulated ink particles. With this system, a double treatment in the presence of 150 mg×L-1 SA and 25 mg×L-1 polydiallyldimethylammonium chloride (PDMAC) or starch lead to a supernatant with a turbidity and COD of 150 NTU and 5500 mg×L-1 respectively....

Coagulation-flocculation of the colloids particles present in the cuttlefish effluents was investigated using a coagulation step with aluminium sulphate (SA), followed by a flocculation step with starch, SiO2 or MgO and then poly dimethyl ammonium chloride (PDMAC), in order to reduce the turbidity and chemical oxygen demand (COD). Kinetic aspects, adsorption equilibrium, pH and conductivity were studied in order to determine the optimum coagulation conditions and SA quantities. The addition of organic polymer as a flocculant agent gave a better performance than the use of salt alone with a reduction of 50% of the SA consumption. Polymer molecular weight of PDMAC and charge density of starch have been also investigated. The best result, which is 90% of removal rate in chemical oxygen demand (COD) and a turbidity value of 7 NTU was obtained with the combination using 165.5 mg l(-1) of aluminium sulphate, 750 mg l(-1) of MgO and 35 mg l(-1) of PDMAC 400000.