ALBERT

Description: This paper reports a physicochemical study (thermodynamic and kinetic data) describing the ability of Rubus ulmifolius biomass (dead leaves) for metal uptake. The toxicity of aluminum is a major problem for crops in acidic soils and therefore, aluminum has been selected. The results obtained indicate that dead R. ulmifolius leaves uptake up to 10000mg/kg on its surface in less than 60min. This suggests that R. ulmifolius can be an excellent component with adsorbent properties for aquatic environments and in particular for amendments to be used in acidic soils in order to control aluminum levels, thus its toxicity. The results obtained have been critically analyzed and compared with literature on aluminum bioaccumulation. The application of a pseudo-second order kinetic equation, not previously used in toxicity studies, is discussed. Moreover, a good linear correlation between stability constants for Al3+ complexes with several defined ligands and the Langmuir affinity constants obtained from the corresponding adsorption isotherm has been found. Therefore, in addition to its ethno-botanical relevance, applications of R. ulmifolius as a detoxifier for aluminum in a simulated acidic gastrointestinal fluid, as phytostabilization agent in amendments or in natural attenuation cycles or as biomass for wastewater treatment containing aluminum, are suggested.

Description: The concept of biosorption results from the “passive” (nonmetabolic) interaction of a chemical species with a particle of a biological material. This interaction can be practically exploited, for example, for removal of toxic substances of wastewaters or for the enrichment of a fertilizer with micronutrients. In this work, equilibrium and dynamic data obtained with “low-cost” biomaterials of algal waste or invasive seaweed species have been reviewed and critically analyzed in the context of a circular economy. The concept of a biosorption unit, oriented to the valorization of any solid residual material of algal biomass, can be considered as a real possibility in a biorefinery process; but to accomplish this goal it is necessary that the emphasis on research must definitely move from laboratory scale toward pilot plant assays.

Description: The analysis of more than 400 papers found in the literature on Sargassum biosorption has shown the existence of more than 700 equilibrium entries corresponding to data at different temperature and pH conditions. The following ten single metals: Cd, Co, Cr(III, VI), Cu, Fe, Hg, La, Ni, Pb, and Zn, are the main focus of most of the equilibrium data (507) in more than half of the studied references. The studies reflecting the interaction of nine of these metals with Sargassum sp. is described and analyzed. The use of Langmuir equation, the effect of temperature and pH on sorption is critically reviewed. In addition, we also analyze all the data available on elemental chemical composition of native Sargassum. These data reflect the interaction of this kind of marine biomass with nine of the metals mentioned above, which are present in seawater worldwide.

Description: A broad variety of materials of biological origin have been successfully used in recent decades for the removal of pollutants from waters. These biosorbents include natural polymers that play a key role for adsorption. It is therefore critical to understand the physicochemical properties of the chemical groups of these biopolymers. The acid–base properties of biomass are affected by pH, ionic strength and medium composition. Nevertheless, these parameters are not always considered during biosorption studies. According to the literature, less than 3% of biosorption reports include studies on proton binding. Moreover, in 60% of these papers, there is key experimental information missing such as the calibration of the electrodes employed for potentiometric titrations. We consider therefore that there is an important need for reviewing the role of proton binding in biosorption studies. This review outlines the major advances on data interpretation and modelling of proton binding on biosorbents. In addition, we discuss issues concerning the acid–base properties of biosorbents.

Description: In this work, water extracts from different bio-based products of plant origin were studied to evaluate their antioxidant capacity and their potential to form metal nanoparticles from aqueous solutions. Two traditional tests, the Folin–Ciocalteu assay and the DPPH radical scavenging capacity method were compared with a more recent one, SNPAC, based on the formation of silver nanoparticles. The silver nanoparticle antioxidant capacity method (SNPAC) was optimized for its application in the characterization of the extracts selected in this work; kinetic studies and extract concentration were also evaluated. The extracts were obtained from leaves of oak, eucalyptus, green tea, white and common thyme, white cedar, mint, rosemary, bay, lemon, and the seaweed Sargassum muticum. The results demonstrate that any of these three methods can be used as a quick test to identify an extract to be employed for nanoparticle formation. Additionally, we studied the synthesis of Cu, Fe, Pb, Ni, and Ag nanoparticles using eucalyptus extracts demonstrating the efficiency of this plant extract to form metallic nanoparticles from aqueous metal salt solutions. Metal nanoparticles were characterized by transmission electron microscopy and dynamic light scattering techniques.

Description: Highlights • A cascade biorefinery process for Sargassum muticum (Sm) was proposed. • Dried sap (2% of raw material) was enriched in K and stimulated stem and root growth. • Similar alginate, phenolics and fucoidan yields and properties to those from unpressed Sm. • Methane production from autohydrolysis solids increased by 55-76% compared to the use of Sm. • The autohydrolysis at a maximum of 150 °C was optimal for different products. Abstract Marine macroalgae represent an excellent material to be used as biogas producer, adsorbent, biostimulant and fertilizer for soils, or feedstock. The success in the exploitation of seaweeds depends on their characteristics, and the approach used to separate their specific active components. In the context of circular economy, invasive species are a good candidate for exploitation, and biorefinery a key valorization technique. Here we investigate a novel biorefinery scheme for a fuller valorization of the alien species Sargassum muticum. An initial pressing stage allowed the production of a Sap fraction, which showed potential as a plant biostimulant, increasing both root development and shoot/root ratio, especially when used at a dose of 0.1 g/L lyophilized Sap. The solids after pressing were processed by non isothermal autohydrolysis, using pressurized hot water under subcritical conditions (120-210 °C), previously optimized to solubilize the fucoidan and phlorotannin fractions. The residual solids remaining after pressing and autohydrolysis stages were evaluated for the production of biogas. The obtained value (150 mL CH4/g residual solids at 150 °C) is significantly higher than that found for the raw seaweed. The optimal autohydrolysis temperature (150 °C) is compatible with the production of the fucoidan fraction, although the phenolic content is favoured at stronger operation conditions. We also discuss the possibility of preparing adsorbents for pollutant removal and mineral amendments from the autohydrolysis waste solids.