Elena Fuente

Waste management from pulp and paper production in the European Union

Eleven million tonnes of waste are produced yearly by the European pulp and paper industry, of which 70% originates from the production of deinked recycled paper. Wastes are very diverse in composition and consist of rejects, different types of sludges and ashes in mills having on-site incineration treatment. The production of pulp and paper from virgin pulp generates less waste but the waste has similar properties to waste from the production of deinked pulp, although with less inorganics. Due to legislation and increased taxes, landfills are quickly being eliminated as a final destination for wastes in Europe, and incineration with energy recovery is becoming the main waste recovery method. Other options such as pyrolysis, gasification, land spreading, composting and reuse as building material are being applied, although research is still needed for optimization of the processes. Due to the large volumes of waste generated, the high moisture content of the waste and the changing waste composition as a result of process conditions, recovery methods are usually expensive and their environmental impact is still uncertain. For this reason, it is necessary to continue research on different applications of wastes, while taking into account the environmental and economic factors of these waste treatments.

Enzymatic approaches in paper industry for pulp refining and biofilm control

The use of enzymes has a high potential in the pulp and paper industry to improve the economics of the paper production process and to achieve, at the same time, a reduced environmental impact. Specific enzymes contribute to reduce the amount of chemicals and energy required for the modification of fibers and helps to prevent the formation or development of biofilms. This review is aimed at presenting the latest progresses made in the application of enzymes as refining aids and biofilm control agents.

Peer Reviewed: The Challenges of Sustainable Papermaking

Although the industry has become more environmentally friendly, it needs to overcome social, economic, and scientific obstacles to achieve additional progress

Separation of Contaminants from Deinking Process Water by Dissolved Air Flotation: Effect of Flocculant Charge Density

Abstract The effect of charge density of 5 cationic polyacrylamides (C-PAMs) and 3 anionic polyacrylamides (A-PAMs) in single and in dual treatments with a coagulant on the flocculation and removal of dissolved and colloidal material by dissolved air flotation (DAF) in papermaking has been studied. In single systems, good results were achieved both with low and high charge C-PAMs (1.0 and 3.0–3.5 meq/g). In dual systems, high charge C-PAMs (3.0–3.5 meq/g) and A-PAMs (1.5 meq/g), were the most efficient. Results show that monitoring flocculation by a focused beam reflectance measurement (FBRM) allows papermakers to optimize the chemical dosages to maximize the separation efficiency of DAF units either with single or dual systems, which is not always possible with traditional methods as charge titration.

Effect of polyelectrolyte morphology and adsorption on the mechanism of nanocellulose flocculation.

The effect of polyelectrolyte morphology, charge density, molecular weight and concentration on the adsorption and flocculation of Microfibrillated Cellulose (MFC) were investigated. Linear Cationic Polyacrylamide (CPAM) and Branched Polyethylenimine (PEI) of varying charge density and molecular weight were added at different dosages to MFC suspensions. The flocculation mechanisms were quantified by measuring gel point by sedimentation, and floc size, strength and reflocculation ability through Focussed Beam Reflectance Measurements. Polymer adsorption was quantified through zeta potential and adsorption measurements using polyelectrolyte titration. The flocculation mechanism of MFC is shown to be dependent on polyelectrolyte morphology. The high molecular weight branched polymer, HPEI formed rigid bridges between the MFC fibres. HPEI had low coverage and negative zeta potential at the optimum flocculation dosage, forming flocs of high strength. After breaking of flocs, total reflocculation was achieved because the high rigidity of polymer did not allow reconformation or flattening of the polyelectrolyte adsorbed on MFC surface. The lower molecular weight branched polymer, LPEI (2kDa) showed rapid total deflocculation, complete reflocculation and had maximum flocculation occurring at the point of zero charge. These characteristics correspond to a charge neutralisation mechanism. However, if the flocculation mechanism was purely charge neutralisation mechanism, the minimum gel point would be at the point of zero charge. Since this is not the case, this difference was attributed to the high polydispersity of the commercial LPEI used, allowing some bridges to be formed by the largest molecules, changing the minimum gel point. With the linear 80% charged 4MDa CPAM, bridging mechanism dominates since maximum flocculation occurred at the minimum gel point, negative zeta potential and low coverage required for maximum flocculation. Reflocculation was not possible as the long linear polymer reconformed on the MFC surface under a flat conformation. Flocculation with the linear 50% charged 13MDa CPAM happened by bridging with the minimum gel point and maximum flocculation corresponding to roughly half polyelectrolyte surface coverage on cellulose.

Interactions between cellulose nanofibers and retention systems in flocculation of recycled fibers

Although the positive effect that cellulose nanofibers (CNF) can have on paper strength is known, their effect on flocculation during papermaking is not well understood, and most relevant studies have been carried out in presence of only cationic starch. Flocculation is the key to ensuring retention of fibers, fines, and fillers, and furthermore floc properties have a great influence on paper quality. The aim of this research is to study the interactions between CNF and flocculants by assessing the effect of two types of CNF, from eucalyptus and corn, on the flocculation process induced by three different retention systems [a dual system, polyvinylamine (PVA), and cationic starch as reference]. The results showed that CNF interacted with the flocculants in different ways, affecting flocculation efficiency and floc properties. In general, addition of CNF increased floc stability and minimized overdosing effects. Moreover, presence of CNF increased floc size for given PVA dose; therefore, CNF addition could contribute to improve the wet end in the paper machine if combined with the optimal flocculant and dose.

Sustainable joint solventless coproduction of glycerol carbonate and ethylene glycol via thermal transesterification of glycerol

This study focuses on the thermal reaction between glycerol and ethylene carbonate to obtain glycerol carbonate and ethylene glycol under solventless homogeneous operation, the process being a transcarbonation of glycerol or a glycerolysis of ethylene carbonate. As the two reagents constitute an immiscible system at 40 °C evolving into a single phase at 80 °C, the evolution of phases with temperature was studied by focused beam reflectance measurement. As the biphasic system was inert, runs were completed under a monophasic regime from 100 to 140 °C with molar ratios of ethylene carbonate to glycerol of 2 and 3, achieving quantitative conversion of glycerol, as corroborated by a thermodynamic study. Second order potential kinetic models were proposed and fitted to the data. Finally, a comparison with analogous catalytic approaches was made, showing that this process performs better material-wise.

Synergies between cellulose nanofibers and retention additives to improve recycled paper properties and the drainage process

Cellulose nanofibers (CNF) have increasing relevance in different applications, for instance, in the paper industry as a sustainable strength additive. This application is especially beneficial for recycled paper, which reaches higher product quality despite its limitations. CNF change paper properties and also can affect the production process, especially the drainage stage, in which retention additives (RA) are commonly used to promote interaction of cellulose fibers. CNF probably interact with fibers and RA, affecting the drainage stage. However, these interactions vary depending on the type and flocculation mechanism of RA. This research is aimed at establishing possible synergies between CNF and RA to improve paper strength, avoiding negative effects on the drainage process. No further RA were used to retain CNF, taking advantage of the RA already used in the process. Polyvinylamine, chitosan, cationic starch, C-PAM, and C-PAM-B were selected as RA. CNF from eucalyptus kraft pulp and corn stalk organosolv pulp were tested. Strength properties of laboratory sheets were studied, and interactions were assessed by measuring Z-potential. Synergies between PVA, chitosan, C-PAM, and C-PAM-B with CNF were found. Drainage time decreased ranging between 30 and more than 40% using CNF. Strength depended on RA and formation quality. Among the studied options, CNF with C-PAM-B or chitosan resulted in the best formation and higher strengths with a significant drainage time reduction.

Cellulose nanofibers from residues to improve linting and mechanical properties of recycled paper

The production of high filler-loaded recycled papers is often affected by high values of linting and low values of strength. In the first case, the accumulation of lint particles from paper’s surface on the printing blanket affects the quality of the printed paper and the pressroom’s productivity. In the second case, increasing the use of fillers and recycling cycles lead to poor paper strength. Cellulose nanofibers (CNFs) are receiving a great deal of attention due to their potential as a reinforcement aid for high filler-loaded papers through filler–fiber interaction and interfiber bonding. It is already proven that high quality CNFs can reduce linting, although their industrial application is limited by their high production cost. The objective of this research is, therefore, to quantify the effect of applying lower grade, more sustainable CNFs on linting phenomena and on the mechanical properties of recycled papers. Eucalyptus, pine and triticale residues were used as cellulose sources, and the CNFs were produced minimizing the chemical pretreatment before homogenization. Addition of 3 wt% of CNFs from pine residues into the recycled paper with 15.7 wt% of total filler reduced linting by 40% and increased tensile strength by 15.1%; further improvements on linting and mechanical properties were achieved at 5 wt%. Moreover, the increase in drainage time can be overcome by the addition of a retention aid, in this case a coagulant-cationic polyacrylamide-bentonite system, commonly used in paper mills.

Effect of Sepiolite on Mechanical and Physical Properties of Fiber Cement

In the time since asbestos was banned, new mixtures have been studied to obtain a product with similar properties to the asbestoscement sheets in the Hatschek process. The aim of this research is to study the effect of two different sepiolites on the physical and mechanical properties of roofing fiber-cement sheets when they contain natural fibers or mixtures of synthetic and natural fibers. Studied properties included bulk density, water absorption, permeable void volume, modulus of rupture, proportional limit, specific energy, and modulus of elasticity. The results showed that fibercement sheets containing sepiolite had better performance in terms of flexural strength and that the characteristics of the sepiolite selected played a key role in the development of the mechanical properties of the fiber-cement products.