Impact of natural degradation of the invasive alga Rugulopteryx okamurae on anaerobic digestion: Heavy metal pollution and kinetic performance.

This study shows, for the first time, how the natural biodegradation of the Phaeophyceae Rugulopteryx okamurae (R.o.) affects its methane yield, by biochemical methane potential assays, and the methane production kinetics. Additionally, a mechanical (zeolite-assisted milling) and a thermal (120 °C, 45 min) pretreatments were assessed. The highest methane yield was obtained from the mechanically pretreated fresh ashore biomass (219 (15) NLCH4 kgVS-1), which presents the use of zeolite during milling as an economical alternative for heavy metal toxicity reduction. Moreover, no significant differences were observed between the other tests (with the exception of the lowest value obtained for the mechanically pretreated fresh R.o.). Low methane yields were linked to the heavy metal content. However, an increase of 28.5 % and 20.0 % in the k value was found for the untreated fresh R.o. biomass and fresh ashore biomass, respectively, when subjected to thermal pretreatment. Finally, an enhancement of 80.5 % in the maximum methane production rate was obtained for the fresh ashore biomass milled with zeolite compared to the untreated fresh ashore biomass.

Turning an invasive alien species into a valuable biomass: Anaerobic digestion of Rugulopteryx okamurae after thermal and new developed low-cost mechanical pretreatments.

The invasive alien seaweed Rugulopteryx okamurae (R.o.) has spread quickly through the Mediterranean Sea causing an unprecedented ecological impact. A solution integrated into a circular economy model is needed in order to curb the negative effects of its presence. Anaerobic digestion (AD) is proposed as a feasible process able to transform biomass into renewable energy. Nevertheless, in order to improve the methane yield and surpass the drawbacks associated with AD processes, this research proposes a thermal pretreatment and a new developed method where the macroalgae is mechanically pretreated with zeolite. Chemical and microstructure characterization of the algal biomass after pretreatments involved scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The highest methane yields of 240 (28) and 250 (20) NLCH4 kg-1 VSadded were obtained with the new mechanical pretreatment and the thermal pretreatment at 120 °C for 45 min without zeolite, achieving a 35 % improvement against the non-pretreated algae. A direct relationship between the crystallinity index of the samples and methane production was observed. The experimental data of methane production versus time were found to be in accordance with both first-order kinetic and Transference Function mathematical models.

Integral Valorization of Two-Phase Olive Mill Solid Waste (OMSW) and Related Washing Waters by Anaerobic Co-digestion of OMSW and the Microalga Raphidocelis subcapitata Cultivated in These Effluents.

This study evaluates the comprehensive valorization of the byproducts derived from the two-phase olive oil elaboration process [i.e., olive washing water (OWW), olive oil washing water (OOWW), and olive mill solid waste (OMSW)] in a closed-loop process. Initially, the microalga Raphidocelis subcapitata was grown using a mixture of OWW and OOWW as the culture medium, allowing phosphate, nitrate, sugars, and soluble chemical oxygen demand removal. In a second step, the microalgal biomass grown in the mixture of washing waters was used as a co-substrate together with OMSW for an anaerobic co-digestion process. The anaerobic co-digestion of the combination of 75% OMSW-25% R. subcapitata enhanced the methane yield by 7.0 and 64.5% compared to the anaerobic digestion of the OMSW and R. subcapitata individually. This schedule of operation allowed for integration of all of the byproducts generated from the two-phase olive oil elaboration process in a full valorization system and the establishment of a circular economy concept for the olive oil industry.

Evaluation and modelling of methane production from corn stover pretreated with various physicochemical techniques.

Lignocellulosic by-products from agricultural crops represent an important raw material for anaerobic digestion and clean renewable, which is a key component of the circular economy. Lignocellulose is recalcitrant to biodegradation and pretreatments are required to increase methane yield during anaerobic digestion. In this work, the efficacy of different physicochemical pretreatments was compared using corn stover biomass as substrate. Anaerobic digestion of untreated and pretreated corn stover was performed in batch mode at mesophilic temperature (38°C) and organic matter solubilization of pretreated substrates was also investigated. The highest organic matter solubilization occurred in autoclave pretreatment (soluble chemical oxygen demand = 5630 ± 42 mg O2 L-1). However, the highest methane yield was obtained using alkaline pretreatment (367 ± 35 mL CH4 g-1 VSadded). Alkaline pretreatment increased methane yield by 43.3% compared to untreated control (256 ± 15 mL CH4 g-1 VSadded). Two mathematical models (i.e. first-order kinetics and transfer function) were utilized to fit the experimental data with the aim of assessing anaerobic biodegradation and to obtain the kinetic constants in all cases studied. Both models adequately fit the experimental results. The kinetic constant, k, of the first-order model increased by 92.8% when stover was pretreated with sulphuric acid compared with control. The transfer function model revealed that the maximum methane production rate, Rm, was obtained for the sulphuric acid treatment, which was 63.5% higher compared to control.

Reactivity towards nitriles, cyanamides, and carbodiimides of palladium complexes derived from benzyl alcohol. Synthesis of a mixed Pd2Ag complex.

The chelate complex [Pd(κ(2)-C,O-C6H4CH2O-2)(bpy)] () reacts with acetonitrile, cyanamides, or carbodiimides, in the presence of AgOTf (1 : 5 : 1 molar ratio) and residual water, to form complexes [Pd{κ(2)-C,N-C6H4{CH2OC([double bond, length as m-dash]NX)Y}-2}(bpy)](OTf), where X = H, Y = Me (), NMe2 (), NEt2 (), X = R, Y = NHR (R = (i)Pr (), Tol ()), as a result of the insertion of the unsaturated reagent into the O-Pd bond of and the protonation of one of the N atoms. In the absence of AgOTf the reaction of with TolN[double bond, length as m-dash]C[double bond, length as m-dash]NTol (Tol = p-Tolyl) results in the formation of the neutral complex [Pd{κ(2)-C,N-C6H4{CH2OC([double bond, length as m-dash]NTol)NTol}-2}(bpy)] (). Complexes and can be interconverted by deprotonation ( + KO(t)Bu) or protonation ( + KOTf + HOTf) reactions. When the reaction of with TolN[double bond, length as m-dash]C[double bond, length as m-dash]NTol in the presence of AgOTf is carried out in a 1 : 1 : 1 stoichiometric ratio, or for a short period of time, a mixture of and a mixed heterometallic Ag2Pd complex is obtained ( = [Ag(N-)2](OTf)). Complex is the major product when the AgOTf is added before the carbodiimide, and the reaction is stopped immediately. can also be obtained by reaction of with 0.5 equiv. of AgOTf. When complex [PdI(C6H4CH2OH-2)(bpy)] () reacts with (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr in the presence of TlOTf, instead of AgOTf, a ca. 1 : 1 mixture of and [Pd{κ(2)-O,N-OCH2{C6H4{C([double bond, length as m-dash]NH(i)Pr)N(i)Pr}-2}}(bpy)](OTf) () forms. Complex is the result of the insertion of the carbodiimide into the C-Pd bond. Complexes have been extensively characterized by NMR spectroscopy, and the crystal structures of , , and ·2.5CHCl3·0.5Et2O have been determined by X-ray diffraction studies.