Enhancing Lignocellulosic Biomass Hydrolysis by Hydrothermal Pretreatment, Extraction of Surface Lignin, Wet Milling and Production of Cellulolytic Enzymes.

Acetone and ethanol extraction of lignin deposits from the surface of hydrothermally (liquid hot water) pretreated beech wood biomass alleviates the lignin inhibitory effects during enzymatic hydrolysis of cellulose to glucose and boosts the enzymatic digestibility to high values (≈70 %). Characterization of the extracted lignins (FTIR, pyrolysis/GC-MS, differential thermogravimetry, gel permeation chromatography) indicated high purity, low molecular weight, and features that suggest that it consists mainly of fragments of the native wood lignin partially depolymerized and recondensed on the biomass surface during the hydrothermal pretreatment. The pyrolysis products of the extracted surface lignins suggest their high potential as a feedstock for the production of high added value phenolic compounds. When the enzymatic hydrolysis of the pretreated and extracted biomass solids was assisted by mild wet milling, near complete cellulose digestibility (≥95 %) could be achieved. In the context of the biorefinery and whole-biomass valorization concept, it was also shown that the hydrothermally (hemicellulose-deficient) pretreated and delignified biomass solids could be also successfully used for the production of crude cellulase from Trichoderma reesei cultures, providing a simple and low-cost method for the complementary production of cellulases by utilizing fractions of the integrated hydrolysis process.

The Change from Past to Future for Adsorbent Materials in Treatment of Dyeing Wastewaters.

Adsorption is one of the most promising decolorization techniques in dyeing wastewater treatment. Adsorption techniques for wastewater treatment have become more popular in recent years owing to their efficiency in the removal of pollutants too stable for biological methods. Dye adsorption is a result of two mechanisms (adsorption and ion exchange) and is influenced by many factors as dye/adsorbent interaction, adsorbent's surface area, particle size, temperature, pH, and contact time. The main advantage of adsorption recently became the use of low-cost materials, which reduces the procedure cost. The present review firstly introduced the technology process, research history and research hotspot of adsorption. Then, the application of adsorption in treatment of dyeing wastewaters in the past decades was summarized, revealing the impressive changes in modes, trends, and conditions. From this review article, the different philosophy of synthesis of adsorbent materials became evident.

Modeling local flotation frequency in a turbulent flow field.

Despite the significance of turbulent fluid motion for enhancing the flotation rate in several industrial processes, there is no unified approach to the modeling of the flotation rate in a turbulent flow field. Appropriate modeling of the local flotation (bubble-particle attachment) rate is the basic constituent for global modeling and prediction of flotation equipment efficiency. Existing approaches for the local flotation rate are limited to specific set of conditions like high or low turbulence. In addition, the combined effects of buoyant bubble rise and/or particle gravity settling are usually ignored. The situation is even vaguer for the computation of collision and attachment efficiencies which are usually computed using the gravity induced velocities although the dominant mode of flotation is the turbulent one. The scope of this work is clear: the development of a general expression for the flotation rate in a turbulent flow field which will cover in a unified and consistent way all possible sets of the problem parameters. This is achieved by using concepts from statistical approach to homogeneous turbulence and gas kinetic theory.

Application of flotation for the separation of metal-loaded zeolites.

Several industrial wastewater streams may contain heavy metal ions, which must be effectively removed, before the discharge or reuse of treated waters could take place. Different bonding materials, presenting selectivity and fast reaction kinetics for the removal of metals, have been examined for this purpose. The objective of the present paper was to investigate the application of dispersed-air flotation for the separation of metal-loaded sorbents. Two similar zeolite samples were applied as effective bonding agents for the removal of zinc, a toxic metal commonly found in many industrial wastewaters. This combined process, termed sorptive flotation, involves the preliminary scavenging of metal ions, by using the appropriate sorbent particles (usually present as ultrafine particulates), followed by flotation for the effective separation of them. The obtained results were very promising, as both metal and sorbent were effectively removed/separated from the dispersion.

Removal of As(V) from wastewaters by chemically modified fungal biomass.

Biosorption has been demonstrated to be a useful alternative to conventional treatment systems for the removal of toxic metals from dilute aqueous solution. The objective of this paper was to examine the main aspects of a possible strategy for the removal of arsenates, employing P. chrysogenum biomass. The pretreatment of biomass with common surfactants (as hexadecyl-trimethylammonium bromide and dodecylamine) and a cationic polyelectrolyte was found to improve the biosorption efficiency. The initial biomass showed a relative low affinity for metallic anions, whereas with the application of modified samples a significant uptake of arsenic was observed. Sorption data were well described by typical Langmuir and Freundlich adsorption isotherms. Promising results were obtained in laboratory experiments and effective As(V) removals were observed.