Efficient Recovery of Lignin and Hemicelluloses from Kraft Black Liquor

Black liquor (BL) from kraft pulping industries contains a large fraction of lignin and hemicelluloses and their efficient separation can open up new possibilities for integrated biorefineries. In this work, lignin and hemicelluloses were separated from BL and concentrated BL (obtained by ultrafiltration), by precipitation using acidification and antisolvent precipitation method, respectively. For lignin precipitation, different organic acids, namely acetic, lactic and citric acid, were used and the yield and purity of the extracted lignin were compared with the lignin precipitated using inorganic acids, namely sulphuric and phosphoric acid. Among the organic acids, the highest yield of lignin (57.2%) was obtained by lactic acid, but the extract also contained the highest levels of inorganic impurities (9.2%). The extract obtained from acetic acid contained lower inorganic impurities and the lignin yield was 48.1%. The hemicellulose was extracted from BL liquor that was concentrated using the ZnObased PES mixed matrix ultrafiltration membrane, which was started by first separating lignin (at pH 3.5, 4 and 4.5) from it. The supernatants from the lignin precipitation process were used as a source of hemicellulose and this was precipitated by using acetone as an antisolvent. The highest hemicellulose yield (54.4%) was obtained from the supernatant with the lowest lignin content and highest acetone to supernatant ratio. Keywords: acidification, antisolvent precipitation, hemicelluloses, kraft black liquor, ligni

Modelização de separações por membrana através de métodos de refinamento de malha

Aplicou-se um modelo que conjuga a polarização da concentração e o transporte numa membrana para simular a ultrafiltração de soluções aquosas de PEG-3400. O problema incorpora o modelo de fricção binária desenvolvido a partir de uma modificação da equação de Maxwell-Stefan-Lightfoot. Desenvolveu-se um método numérico adaptativo eficiente para resolver simultaneamente as duas partes do modelo (camada de polarização e membrana). A resolução numérica do sistema algébrico-diferencial permitiu a ilustração adequada do fenómeno de rejeição aparente de soluto (em soluções aquosas de PEG-3400) assim como da queda de pressão em função do fluxo. Por outro lado, possibilitou a previsão adequada da influência de parâmetros físico-químicos e das condições de operação nesses fenómenos de rejeição, para além da correcta formação dos perfis de concentração e de fluxo quer na zona da camada de polarização como da membrana. A comparação com valores experimentais de ultrafiltração possibilita a validação do modelo no caso específico das soluções de PEG-3400. Os resultados de simulação dependem significativamente das características de resistência, Rm, da membrana que manifestam uma grande variabilidade de ensaio para ensaio e que influenciam o valor do coeficiente de equilíbrio, Keq

Urban wastewater as a source of reclaimed water for irrigation: barriers and future possibilities

Water resources are under pressure worldwide, resulting in scarcity and deterioration of freshwater quality. According to European directives, we could reduce the pressure on water resources in urban areas by increasing the reuse of treated wastewater, reducing the impact on water bodies, and promoting water recycling through multiple uses of urban wastewater. Besides the need to address water supply challenges, wastewater treatment systems show environmental stewardship and innovative practices. Using reclaimed water for agricultural irrigation is gaining interest because of the drought conditions experienced in Europe over the past few years. Furthermore, using treated wastewater for agricultural irrigation may help to restore nutrients (N and P) to natural biogeochemical cycles. This review highlights the importance of water reuse, current legislation, and existing technologies to implement in wastewater treatment systems to meet the minimum requirements to produce reclaimed water to reuse in agricultural irrigation.info:eu-repo/semantics/publishedVersio

Simulation of membrane separations using a modified Maxwell-Stefan model

A modified Maxwell-Stefan model, which considers both the concentration polarization and the transport through the membrane, is tested for the simulation of Dextran-98000 aqueous solutions filtration. The model is able to successfully simulate experimental data in the high rejection/low flux region, but does replicate the observed rejection drop/pressure build-up which occurs for increased fluxes, which may be due to limitations of the model itself

Lignin Recovery from Black Liquor Using Integrated UF/NF Processes and Economic Analysis

Lignin is a polyphenolic biopolymer present in large amounts in black liquor (BL). This work investigated the recovery of lignin from BL (pre-filtered by ultrafiltration (UF)) by nanofiltration (NF). For the NF tests, laboratory-made mixed matrix membrane (MMM) prepared with 0.1% activated carbon (AC) nanoparticles were used in crossflow filtration mode. The effect of pressure (6–15 bar) and volume reduction (VR) (~65%) were analyzed, and the filtration performance was evaluated in terms of permeate flux, lignin rejection rate, and flux reduction. The lignin rejection rate varied in the range of 67–80% with the pressure, however, the highest increases in flux and rejection were observed at 12 bar, which was found to be the optimum pressure. At a VR of ~65%, the permeate flux decreased by ~55% and the lignin rejection rate increased from 78% to 86%. In addition, an economic evaluation was performed for the preparation of UF and NF MMM. The minimum-to-maximum price range was estimated considering the costs of the laboratory and commercial grade regents. It showed a difference of ~10-fold and ~14-fold for UF and NF membranes, respectively. The results of the laboratory-scale study were used to evaluate the economic feasibility of the process for recovering lignin- and hemicellulose-rich retentate streams

Agronomic valorization of sewage sludge: The potential of thermal drying to achieve sanitation and biological stability

This work aims to contribute to the discussion of using a waste (sewage sludge) to obtain a valuable product (organic-rich fertilizer), based on a circular economy perspective. The compo- sition of sewage sludge (SS) was considered, highlighting important characteristics as raw ma- terial for fertilizer production (e.g., macronutrients, microbiological contamination, phytotoxicity). Particularly, the biological stability of SS was evaluated measuring the oxygen uptake rate (OUR) using the Oxitop® method, and the phytotoxicity using germination tests. The potential of thermal drying to stabilize the SS was evaluated at two temperatures (100 and 130◦C). The results showed that the organic matter (OM), N, and P levels are within the range of interest for agronomic valorization, while the content of some potentially toxic metals (e.g., Zn and Cu) may exceed the legal limits. The phytotoxicity assessment showed that raw SS samples negatively impacted the germination phase. Concerning the biological stability, results showed that raw anaerobic digested samples were characterized by OUR values above 50 mmol O2/kg OM.h (the limit for stable SS). Although thermal treatment of SS at 100 and 130◦C eliminated pathogens and significantly stabilized SS to OUR values below 50 mmol O2/kg OM.h, it was not enough to reach the limit established for a stable fertilizer (25 mmol O2/kg OM.h). Globally, SS has potential for soil application, within the scope of circular economy, but it is essential to control its microbiological contamination and stability.info:eu-repo/semantics/publishedVersio

Recent Advances in Valorization Methods of Inorganic/Organic Solid, Liquid, and Gas Wastes

The main goal of this special issue was to gather contributions dealing with the latest breakthrough methods for providing value compounds and energy/fuel from waste valorization. Valorization is a relatively new approach in the area of industrial wastes management, a key issue to promote sustainable development. In this field, the recovery of value-added substances, such as antioxidants, proteins, vitamins, and so forth, from the processing of agroindustrial byproducts, is worth mentioning. Another important valorization approach is the use of biogas from waste treatment plants for the production of energy. Several approaches involving physical and chemical processes, thermal and biological processes that ensure reduced emissions and energy consumptions were taken into account. The papers selected for this topical issue represent some of the mostly researched methods that currently promote the valorization of wastes to energy and useful materials ..

Development of polyethersulphone mixed matrix zeolite membranes functionalized with ionic liquids and deep eutectic solvents for CO2 separation

Mixed matrix membranes (MMM) combine the flexibility of polymers and the strength and durability presented by inorganic solidsinfo:eu-repo/semantics/publishedVersio

Recent Advances in Valorization Methods of Inorganic/Organic Solid, Liquid, and Gas Wastes

The main goal of this special issue was to gather contributions dealing with the latest breakthrough methods for providing value compounds and energy/fuel from waste valorization. Valorization is a relatively new approach in the area of industrial wastes management, a key issue to promote sustainable development. In this field, the recovery of value-added substances, such as antioxidants, proteins, vitamins, and so forth, from the processing of agroindustrial byproducts, is worth mentioning. Another important valorization approach is the use of biogas from waste treatment plants for the production of energy. Several approaches involving physical and chemical processes, thermal and biological processes that ensure reduced emissions and energy consumptions were taken into account. The papers selected for this topical issue represent some of the mostly researched methods that currently promote the valorization of wastes to energy and useful materials ..