Latour, IsabelMiranda Carreño, RubénBlanco Suárez, María Ángeles2023-06-192023-06-192014Latour, Isabel, et al. «Silica Removal in Industrial Effluents with High Silica Content and Low Hardness». Environmental Science and Pollution Research, vol. 21, n.o 16, agosto de 2014, pp. 9832-42. DOI.org (Crossref), https://doi.org/10.1007/s11356-014-2906-8.0944-134410.1007/s11356-014-2906-8https://hdl.handle.net/20.500.14352/33920High silica content of paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content which makes necessary the addition of magnesium compounds to increase silica removal. Two soluble magnesium compounds (MgCl2∙6H2O and MgSO4∙7H2O) were tested at five dosages (250-1500 mg/L) and different initial pHs. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 mS/cm to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)2 instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15% vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.engjournal article1614-7499http://doi.org/10.1007/s11356-014-2906-8open access67666.0Silica removalMagnesiumSofteningCo-precipitationMembranes foulingEffluent reusePaper recyclingIndustria del papelIngeniería químicaResiduos3312.13 Tecnología de la Madera3303 Ingeniería y Tecnología Químicas