An Investigation into the Stability Source of Collagen Fiber Modified Using Cr(III): An Adsorption Isotherm Study.

The enhanced hydrothermal stability of leather, imparted by little Cr(III), has traditionally been ascribed to strong coordinate bonds. However, this explanation falls short when considering that the heat-induced shrinking of collagen fiber is predominantly driven by rupturing weak H-bonds. This study explored the stability source via adsorption thermodynamics using collagen fiber as an adsorbent. Eleven isotherm models were fitted with the equilibrium dataset. Nine of these models aptly described Cr(III) adsorption based on the physical interpretations of model parameters and error functions. The adsorption equilibrium constants from six models could be transformed into dimensionless thermodynamic equilibrium constants. Based on the higher R2 of the van't Hoff equation, thermodynamic parameters (∆G°, ∆H°, ∆S°) from the Fritz-Shluender isotherm model revealed that the adsorption process typifies endothermic and spontaneous chemisorption, emphasizing entropy increase as the primary driver of Cr(III) bonding with collagen. Thus, the release of bound H2O from collagen is identified as the stability source of collagen fiber modified by Cr(III). This research not only clarifies the selection and applicability of the isotherm model in a specific aqueous system but also identifies entropy, rather than enthalpy, as the principal stability source of Cr-leather. These insights facilitate the development of novel methods to obtain stable collagen-based material.

Highly efficient U(VI) capture from nuclear wastewater by an easily synthesized lignin-derived biochar: Adsorption performance and mechanism.

The efficient recycling of uranium (U) by adsorbents remains challenging due to the strong interference from coexisting impurities, insufficient desorption efficiency, and weak irradiation instability. In this work, a novel lignin-derived biochar (AL/BC) with high surface area and abundant functional groups was developed through a green and simple pyrolysis process, and an adsorbent for U(VI) capture was used. The optimist AL/BC-600 exhibited ultrahigh adsorption capacity for U(VI) of 4007 mg/g, possessing a wide pH range of 1-11, and powerful anti-interference ability when coexisting with various common cations and anions. In addition, AL/BC-600 showed high tolerance even under strong irradiation at a dose of 350 kGy. Most importantly, after the tenth round of the adsorption-desorption cyclic utilization, the adsorption efficiency and desorption rate of AL/BC-600 were actually over 95% and 80%, respectively. Hence, this study provides a green and simple process for synthesizing a novel adsorbent for highly efficient U(VI) capture, not only paving a path for alleviating the increasingly serious energy crisis, but also facilitating the low-carbon and circular development of lignin.

Simultaneously efficient adsorption and highly selective separation of U(VI) and Th(IV) by surface-functionalized lignin nanoparticles: A novel pH-dependent process.

The simultaneous removal and selective separation of U(VI) and Th(IV) via adsorption remain challenging due to their strong mobility, reactivity, and similar chemical properties. Thus, a surface-functioned lignin nanoparticle (AL-PEI) was synthesized to adsorb U(VI)/Th(IV) in a unitary system via a pH-dependent process. In alkaline solution, AL-PEI exhibited excellent adsorption performance, and the maximum adsorption capacities for U(VI) and Th(IV) reached 392 and 396 mg/g, respectively. Discrepantly in acidic solution, the adsorption performance of AL-PEI for U(VI) could still reach a high capacity (332 mg/g), whereas highly limited adsorption capacity (less than 40 mg/g) for Th(IV) was obtained, and the separation factor of U(VI) from U(VI)-Th(IV) matrix significantly reached 6662 in 3 M of the HNO3 medium. The simultaneously efficient adsorption in alkaline solution and highly selective separation performance in acidic solution of AL-PEI also showed excellent anti-ions interference capacities, high reusability, and strong stability. This study is the first to apply lignin fabricating radiation-resistant adsorbent material, and the adsorbent displays good performance for U(VI)/Th(IV) removal and selective separation via a novel pH-dependent process, which is important to the green and sustainable development of nuclear energy and environmental protection.

Graphitic N-doped biochar for superefficient uranium recycling from nuclear wastewater.

N-doped biochar (AL-N/BC) prepared by pyrolyzing lignin in various temperatures manifested superefficient performance for uranium (U) recycling from nuclear wastewater. The optimist AL-N/BC-700 showed higher adsorption capacity of 25,000 mg/g and faster kinetics of 4100 g·min-1·mg-1 than the most of reported adsorbents, and excellent adsorption-desorption capability (adsorption rate > 90 % and desorption rate > 70 % after 12 cycles). Moreover, the high applicability of AL-N/BC-700 was verified by its superefficient U(VI) adsorption performance in a broad working pH range, various water matrices, and high irradiation stability. Furthermore, the adsorption mechanism discloses the significant role of graphitic N, rather than pyridinic N or pyrrolic N, for U(VI) adsorption. Overall, this work not only presents an applicable approach to alleviate the increasingly serious energy crisis via recycling U(VI) from nuclear wastewater, but also enriches the method of synthesizing N-doped materials for U(VI) adsorption.

Reductive immobilization of Cr(VI) in contaminated water by tannic acid.

The rapid reductive immobilization of Cr(VI) from the aqueous solution was achieved by reduction to Cr(III) using tannic acid (TA), and subsequent pH-triggering precipitation of the organo-Cr(III) complexes formed in the redox reaction. The effects of TA concentration, temperature, and solution pH on the reduction of Cr(VI) were examined by batch experiments, and the rapid redox reduction followed a second-order kinetics with respect to Cr(VI) concentration in the pH range of 2.0-3.0. UV-visible spectra, FTIR, and XPS confirmed the complete detoxification of Cr(VI) concomitant with carboxylation of partial phenolic hydroxyls in TA. Synchronously, the reduced Cr(III) coordinated with carboxyl groups in oxidized TA (OTA) to form complexes, which exhibited remarkable pH-dependent size distribution characteristics as illustrated by SEM images and sequential filtration/ultrafiltration. The resulted Cr(III) complexes could aggregate into colloids with larger size and precipitate out at pH range of 6.0-8.0 via cross-linking, thereby leading to 93% Cr and 89% TOC immobilization. An eco-friendly and cost-effective method for Cr(VI) elimination and immobilization is provided because polyphenols are natural polymers derived from plants.

Ecotoxicity and micellization behavior of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and its mixtures with nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO).

Surfactant mixtures have extensive industrial applications due to their ideal properties and low ecotoxicity. However, the ecotoxicity of surfactant mixtures with different proportions and their correlation with surface properties have remained poorly investigated. In this study, the ecotoxicity and surface activity of the composites of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO) in various mass ratios were assessed, and the correlation between ideal application properties and safe ecological perspective of the composites was explored. The ecotoxicity of individual SDBS, AEO, and SDBS/AEO mixtures was determined using the bioluminescence inhibition assay with Photobacterium phosphoreum, and the critical micelle concentrations (CMC) were measured by surface tension method and steady-state fluorescence spectroscopy. Sodium dodecylbenzene sulfonate (SDBS) showed a considerably higher toxicity than individual AEO and SDBS/AEO mixtures. Scanning electron microscope images illustrated the rupture of bacteria membrane induced by SDBS, and the addition of AEO alleviated the damage. According to the dose-response relationship on luminous bacteria, SDBS/AEO mixtures were divided into three groups (group I with a high proportion of SDBS, SDBS:AEO = 4:1 and 3:2; group II, SDBS:AEO = 1:1; group III with a high proportion of AEO, SDBS:AEO = 2:3 and 1:4). The sequence of toxicity of the SDBS/AEO mixtures was group II > group III > group I, demonstrating that the toxicity of the composites was related to the mixture proportion instead of the amount of AEO added. The CMC order of SDBS/AEO mixtures was group II > group I > group III, and it was proportion dependent. Furthermore, ΔCM was defined as the difference of the experimental (CM) and ideal CMC (CMideal) of the mixed system, indicating the interaction between the two kinds of surfactants. The order of the ΔCM was group II > group III > group I, which was consistent with the sequence of the toxicity. Therefore, ΔCM can be a potential indicator for the hazardous assessment of surfactant mixtures involving high ionic strength.