Health and environmental safety aspects of friction grinding and spray drying of microfibrillated cellulose

Abstract

Microfibrillated cellulose (MFC), also referred to as nanocellulose, is one of the most promising innovations for forest sector. MFC is produced by fibrillating the fibres under high compression and shear forces. In this study we evaluated the worker exposures to particles in air during grinding and spray drying of birch cellulose. Processing of MFC with either a friction grinder or a spray dryer did not cause significant exposure to particles during normal operation. Grinding generated small amount of particles, which were mostly removed by fume hood. Spray dryer leaked particles when duct valve was closed, but when correctly operated the exposure to particles was low or nonexistent. To assess the health effects of the produced MFC, mouse macrophages and human monocyte derived macrophages were exposed to MFC and the viability and cytokine profile of the cells were studied thereafter. No evidence of inflammatory effects or cytotoxicity on mouse and human macrophages was observed after 6 and 24 h exposure to the materials studied. The results of toxicity studies suggest that the friction ground MFC is not cytotoxic and does not cause any effects on inflammatory system in macrophages. In addition, environmental safety of MFC was studied with ecotoxicity test. Acute environmental toxicity assessed with kinetic luminescent bacteria test showed high NOEC values ([100 mg/l) for studied MFC. However, MFC disturbed Daphnia magna mobility mechanically when the test was performed according to the standard procedure.

Flocculation of microfibrillated cellulose in shear flow

“…Previously, the pulp used as starting material has been determined to have the negative charge density of 65 leq/g by conductometric titration . The resulting MFC has been reported to contain approximately 27 % hemicelluloses ) and the fiber diameters have been measured to be between 10 and 30 nm with some larger fibril aggregates (Vartiainen et al 2011). Dilution of the suspension was made with deionized Milli-Q water (electrical conductivity \0.2 lS/cm at 25°C) in order to avoid excess electrolytes.…”

“…Today, oxidation (Saito et al 2006) or enzymatic (Pääkkö et al 2007) pretreatments can be used prior to mechanical treatment to lower the energy demand in the disintegration step and to modify the fiber surface. Depending on the manufacturing procedure, the fibers may be single fibrils but most commonly they consist of fibrils and fibril aggregates having a diameter between 5 and 30 nm and a high aspect ratio (Vartiainen et al 2011).…”

A Review of Natural Fiber Reinforced Poly(Vinyl Alcohol) Based Composites: Application and Opportunity

“…Previous studies have assessed the risk of nanocellulose via in vivo and in vitro model. No worrying effects on environment and life are noticed [78][79][80][81]. Thus, the full utilization of PVA/natural fiber composites and their nanocomposites is expected in the future for the benefit of the world.…”

Obtenção de espumas flexíveis de poliuretano com celulose de Pinus elliottii

“…A escolha do método de secagem da nanocelulose é um desafio na área tecnológica devido a sua natureza hidrofílica, com a necessidade de diminuição de etapas de processo para redução de custos além de garantir que sejam mantidas as características nanométricas das fibras, evitando a sua aglomeração. Devido à fibrilação, a superfície da celulose fica exposta a uma maior concentração de grupos hidroxilas, que tendem a formar ligações de hidrogênio com as fibras vizinhas, dificultando a dispersão da celulose e formando emaranhados parcialmente reversíveis ou irreversíveis [16,[26][27][28] . Dentre as várias técnicas conhecidas para secagem, a realizada por aspersão (spray dry) é uma das mais comumente utilizadas na indústria para secagem de suspensões aquosas.…”