International Journal of Biological Macromolecules 82 (2016) 927–932 Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l h o mepa ge: www.elsevier.com/locate/ijbiomac Sodium lignosulfonate as a renewable stabilizing agent for aqueous alumina suspensions Jackson D. Megiatto Jr. a , Bianca M. Cerrutti b , Elisabete Frollini b,∗ a Institute of Chemistry, University of Campinas (UNICAMP), PO Box 6154, Campinas, SP 13083-970 Brazil b Macromolecular Materials and Lignocellulosic Fibers Group, Center for Science and Technology of BioResources, Institute of Chemistry of São Carlos, University of São Paulo, CP 780, 13560-970 São Carlos, São Paulo, Brazil a r t i c l e i n f o Article history: Received 8 September 2015 Received in revised form 14 October 2015 Accepted 1 November 2015 Available online 4 November 2015 Keywords: Sodium lignosulfonate Colloidal alumina FOQELS a b s t r a c t The macromolecule sodium lignosulfonate (SL) has been investigated as dispersing agent for aqueous alumina colloids as a renewable alternative to usual petrochemical stabilizing agents. Optimization of the SL concentration necessary to stabilize the alumina suspension at different pH values was determined by viscometer. The results showed that addition of 250 ppm of the total suspension mass led to about 70% viscosity reduction of the suspension, whereas zeta potential analysis revealed negative values for the SL suspensions throughout the pH range investigated, suggesting that the alumina particles were covered by negatively charged SL molecules. Particle size investigation informed that the average particle diameter of the SL suspensions was smaller compared to that of the pristine particles. Sedimentation time for the SL suspensions was dramatically longer than that for the pristine one. The reported data strongly corroborated that SL is a suitable renewable dispersing agent for aqueous alumina colloids. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Environmental concerns and fast depleting of nonrenewable sources have driven several efforts to redesign well-established industrial processes in order to maximize incorporation of renewable feedstock into the final products. Furthermore, these redesigned processes should prevent waste generation or find alternative waste disposal rather than treatment followed by dis- charge into the environment. In this context, biomass has attracted considerable attention as a renewable source for chemicals, fuels and materials. Particularly, lignin and its derivatives, which are produced as byproducts in the pulp and paper industry and in biore- fineries that produce ethanol from lignocellulosic materials, have been the focus of intensive efforts [1–15]. For example, lignin has proved to be an excellent candidate to partially replace nonrenewable phenol in formaldehyde–phenolic type resins as well as in their composite materials reinforced with vegetable fibers [16–23]. Hydroxymethyl lignins can also work as coupling agents between sisal fibers and formaldehyde-phenolic resins to improve adhesion at the interface of composite mate- rials [24]. Lignosulfonates, an important class of water soluble lignin derivatives generated as waste during the sulfite pulping ∗ Corresponding author. E-mail address: elisabete@iqsc.usp.br (E. Frollini). processing of wood to produce paper, has also been successfully used in polyurethane (PU) formulations to prepare PU-based com- posites with superior mechanical properties compared to those of the pristine materials [25–27]. All those applications benefit from the multi-functionality and macromolecular structure of lignins and their derivatives. In the case of lignosulfonates, the sulfonic groups ( SO 3 H) introduced on their structures during the pulping process remain deprotonated in aqueous medium in a wide pH range (Fig. 1). There- fore, lignosulfonate macromolecules are negatively charged when dissolved in water. Those negative charges associated with their macromolecular structure and water solubility enable lignosul- fonates to act as polyelectrolytes in aqueous medium. Accordingly, lignosulfonates can be renewable alternatives to oil-based poly- electrolytes traditionally used in several industries [9,12,15,28–34]. For example, modified high-molecular mass lignosulfonate-based polymers have proved to be excellent dispersing agents for coal–water slurries [35]. Aluminum oxide or alumina (Al 2 O 3 ) is one of the most used inorganic oxides to prepare high-performance ceramic materi- als. The usual method to produce those ceramic materials is the colloidal processing, which requires aqueous alumina suspen- sions with high solid concentration. At high concentration level, thermal motion promotes collisions among the fine alumina par- ticles in suspension that ultimately lead to spontaneous formation of large aggregates. These large aggregates cause the colloid to http://dx.doi.org/10.1016/j.ijbiomac.2015.11.004 0141-8130/© 2015 Elsevier B.V. All rights reserved.