Current Issue : October-December Volume : 2025 Issue Number : 4 Articles : 5 Articles
The accurate determination of volatile fatty acids (VFAs) and total alkalinity (TAC, mostly carried by bicarbonate ions) is critical for operating anaerobic digesters. The FOS/TAC titration method developed by Nordmann is widely used due to its simplicity and affordability. This method has known limitations in dosing VFAs and TAC, since the presence of one interferes with the determination of the other, especially at higher VFA or bicarbonate concentrations. This study builds upon our prior research in 2021 by integrating the influence of phosphate (H2PO4 −/HPO4 2−) into numerical models correcting FOS/TAC titration results. A Scilab-based program was used to assess the impact of phosphate on titration results, revealing significant biases at lower concentrations. A revised multivariate regression formula was developed, incorporating phosphate effects, and demonstrating superior accuracy. The mean absolute percentage errors (MAPE) for TAC and VFA estimation were reduced to less than 0.3%. The model maintains compatibility with standard Nordmann’s titration protocols and equipment while significantly improving reliability. These findings highlight the necessity of considering phosphate interference in FOS/TAC titration, particularly in AD systems with variable buffering conditions. The proposed correction model enhances process monitoring and control, providing a more robust tool for both research and industrial practice in anaerobic digestion....
The purification of waste cooking oils (WCOs) through clay-based adsorption is an established recycling method, yet the relationship between clay composition and adsorption efficiency remains an area of active research. The aim of the present research work was to assess the performance of Maghnia bentonite in WCO decoloration and to gain information about the specific refining process. Thus, natural bentonite from the Maghnia region (Algeria) was investigated as an adsorbent for WCO refining for biolubricant production. The adsorption efficiency was evaluated under different conditions, achieving up to 70% decolorization at 10 wt% clay after 4 h of treatment. Structural characterization of the bentonite before and after adsorption was conducted using FT-IR spectroscopy, powder X-ray diffraction (XRD), and X-ray fluorescence (XRF) to assess compositional and morphological changes. FT-IR analysis confirmed the adsorption of organic compounds, XRD indicated minor alterations in interlayer spacing, and XRF revealed ion exchange mechanisms, including a reduction in sodium and magnesium and an increase in calcium and potassium. Adsorption kinetics followed a pseudo-second-order model, with desorption effects observed at prolonged contact times. The pHPZC of 8.3 suggested that bentonite adsorption efficiency is enhanced under acidic conditions. The high decoloration capacity of Maghnia bentonite, combined with the availability and the low cost of the material, suggests a possible industrial application of this material for WCO refinement, especially in lubricant production....
A novel polyhedron-based anionic Er-MOF with three types of cages and abundant open metal sites (OMSs) and Lewis base sites (LBSs) has been successfully synthesized. The inorganic secondary unit possesses a rarely reported six-connected three-nucleated rare-earth cluster, and the overall framework shows a new (3,3,6)-connected topology. The Er-MOF has good fluorescence selectivity and anti-interference performance with Fe3+ and Cu2+. In addition, benefiting from the anionic framework, nanoscale cavity and small window size of the Er-MOF, the composite RhB@Er-MOF has been synthesized by in situ encapsulation of the cationic dye Rhodamine B (RhB). It can provide dual-emitting fluorescence that facilitates self-calibration in sensing. The RhB@Er-MOF has higher accuracy than the Er-MOF with regard to the fluorescence-selective and anti-interference performance of Fe3+ and quenching coefficient Ksv values of 1.97 × 104 M−1, which are attributed to its self-calibration function that can eliminate environmental interference. The fluorescence quenching mechanism was explained by our experiments and density functional theory (DFT) calculations. Furthermore, RhB@Er-MOF can achieve the visual and rapid selective detection of Fe3+ by a smartphone RGB color analysis application, resulting in the dual-signal output performance of the material....
Coordination polymers [Gd2(5-iip)3(DMF)4]·0.4DMF (1) and [Dy2(5-iip)3DMF2] ·0.33DMF (2) (5-iip2−—5-iodoisophthalate) feature two different structural types, as follows from X-ray diffractometry data. We prepared and characterized an extended series of corresponding heterometallic complexes of the composition [GdxDy2−x(5-iip)3DMF2]·0.33DMF and [EuxDy2−x(5-iip)3DMF2]·0.33DMF, where x = 0.2, 0.4. . .1.8, and examined the changes of their luminescent properties induced by variations of metal composition, finding the promising white emission sources with high light purity....
The preparation of stable dispersions of MoS2 by ultrasonic aqueous and/or organic media containing amphiphilic molecules is an attractive and widely applicable method to form MoS2 fine particles while suppressing its aggregation. In this study, we developed a series of polymers with pendant sulfide moieties as a new dispersant, under the hypothesis that it would interact with sulfur atoms on MoS2 surfaces. First, we designed a sulfide group-substituted methacrylate derivative (ESMA) with the hypothesis that it would interact with the MoS2 surface through sulfur-sulfur interactions. Then, we synthesized well-defined polymers with pendant sulfide groups by living radical polymerization (ATRP). Next, 0.5 wt% MoS2 was added to a DMSO solution containing 1 wt% of the obtained polymer (polyESMA), and the mixture was treated with a bath-type ultrasonicator for 3 h to obtain a MoS2 dispersion. We found that stable dispersions of MoS2 in a fine particle state, although not in the form of single-layer or few-layer nanosheets, could be readily formed in DMSO using polyESMA as a polymeric dispersant. Furthermore, we synthesized polymeric dispersants with different molecular weights and investigated the relationship between the structure of the dispersant and the dispersion stability....
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