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Boron removal was evaluated in the present work by using calcium alginate beads (CA) and a novel composite based on alginate–alumina (CAAl) as sorbents in a batch system. The effects of different parameters such as pH, temperature, contact time, and composition of alginate (at different concentrations of guluronic and mannuronic acids) on boron sorption were investigated. The results confirm that calcium alginate beads (CA) exhibited a better adsorption capacity in a slightly basic medium, and the composite alginate–alumina (CAAl) exhibited improved boron removal at neutral pH. Sorption isotherm studies were performed and the Langmuir isotherm model was found to fit the experimental data. The maximum sorption capacities were 4.5 mmol g-1 and 5.2 mmol g-1, using CA and CAAl, respectively. Thermodynamic parameters such as change in free energy (¿G0), enthalpy (¿H0), and entropy (¿S0) were also determined. The pseudo-first-order and pseudo-second-order rate equations (PFORE and PSORE, respectively) were tested to fit the kinetic data; the experimental results can be better described with PSORE. The regeneration of the loaded sorbents was demonstrated by using dilute HCl solution (distilled water at pH 3) as eluent for metal recovery., Peer Reviewed, Postprint (published version)

BACKGROUNDA column sorption study was carried out using calcium alginate gel beads as adsorbent for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of pH, initial concentration of boron, feed flow rate, adsorbent mass and column diameter. The breakthrough capacity values and adsorption percentage of calcium alginate gel for boron were calculated. Column data obtained at different conditions were described using the Adams-Bohart model and bed-depth service time (BDST), derived from the Adams-Bohart equation to predict breakthrough curves and to determine the characteristic column parameters required for process design.; RESULTSThe maximum adsorption percentage of boron on calcium alginate gel beads using an initial concentration of boron of 50 mg L-1 at pH 11 and room temperature (201 degrees C) was calculated to be 55.14%.; CONCLUSION

In this work, the removal of boron by a biopolymer of alginate was studied in an aqueous solution. The effects of pH, initial boron concentration, alginate concentration in the beads and stirring time were evaluated. The ratio of mannuronic acid to guluronic acid (M/G) in the alginic acid used in this study was determined by NMR. FTIR spectroscopy was used to characterize the alginate and to observe the interactions produced by the boron adsorbed onto the beads. The maximum boron removal observed was 94 mg/g; this rate was obtained with a high initial boron concentration in an alkaline medium. A study of the isotherms established that the experimental data conform better to the Langmuir than the Freundlich isotherm model. The results obtained in the kinetic studies showed that the pseudo-second-order adsorption model is predominant and that the overall rate of boron adsorption appears to be controlled by chemisorptions., Peer Reviewed, Postprint (published version)

La sostenibilitat de l’ús de l’aigua esta lligada de forma fonamental al seu ús en l’agricultura. L’activitat agrària afecta directament la qualitat de les aigües. Els residus de fertilitzants i de productes fitosanitaris, entre ells els herbicides, constitueixen una font de contaminació del sòl, els quals a través de processos d’escorrentia i infiltració alteren la qualitat de diferents masses d’aigua. La detecció de residus d’herbicides i els seus metabòlits en les aigües dels rius i el mar fa que la eliminació d’aquets productes orgànics, molts d’ells tòxics, s’hagi convertit en un dels problemes mediambientals més importants. Per tal de intentar solucionar aquest problema s’han realitzat nombrosos estudis sobre la eliminació d’aquests compostos mitjançant diferents processos, essent uns del més utilitzats el procés d’adsorció. En les últimes dècades, la utilització de biopolímers com adsorbents per la eliminació de compostos orgànics de les aigües residuals ha demostrat ser eficaç., Peer Reviewed, Postprint (published version)