Construction of Cu-N coordination into natural biopolymer lignin backbone for highly efficient and selective removal of cationic dyes

Bio-inspired porous adsorbents with lotus-leaf-like hierarchical structures and mussel adhesive surfaces for high-capacity removal of toxic dyes

Basic dyes are highly toxic and have adverse effects on humans such as accelerated heart rate, shock, cyanosis, and tissue necrosis upon ingestion or skin contact. Efficient removal of basic dye pollutants from wastewater is therefore essential for the protection of the environment and human health. Biomolecules exhibit excellent dye removal performance in terms of removal capacity, selectivity, and rate. However, their poor thermal/chemical stability precludes their large-scale industrial applications. Herein, porous aromatic frameworks (PAFs) were utilized for the biomimetic construction of mussel, which included two unique features: (1) multistage pore structures for the rapid transport of dye contaminants and (2) mussel-inspired adhesive surfaces for cationic dye removal. Accordingly, the solid PAFs exhibited a record adsorption capacity of 7300 mg g-1 and ultrahigh adsorption rates for cationic dye (safranine T) (188.78 mg g-1 min-1 in the first 20 min). Notably, the bionic adsorbent system exhibited outstanding dye removal performance under various conditions such as after multiple reuse cycles, acid/alkali environments, presence of multiple anions, and in different water bodies (e.g., seawater, lake water, rainwater, and sanitary wastewater). This demonstrates the broad adaptability of the system and its ability to effectively deal with dye contamination in a variety of environments.

Thermophilic lignin-based laccase nanozyme with CuNx center for the detection of epinephrine and degradation of phenolic pollutants

Natural laccases are a family of multi‑copper oxidases that can oxidize multiple phenol substrates and of great importance to contaminant remediation and biosensing. However, the construction of substitutes for the expensive and perishable laccase used in harsh conditions remains a great challenge. Here, we reported a novel strategy for the fabrication of copper-doped lignin-based laccase nanozymes (Cu-AL) through the coordination of aminated lignin and different copper sources. The Cu-AL prepared from CuSO4, possessed highest Cu content and Cu+ proportion, exhibited the best laccase-like activity to various phenols degradation. Strikingly, the thermophilic Cu-AL exhibited superior catalytic activity at 100 °C (3.23 times than that of 60 °C) and durability (> 50 % activity even after 160 days stored in water). Furthermore, a smartphone-based detection platform was successfully developed to achieve the rapid, convenient, and accurate detection of epinephrine concentration. In summary, this work provides a new sustainable and low-cost way to design robust laccase nanozymes from lignocellulose biomass, especially for expanding the applications of enzymatic reaction with high-temperature operation and/or long-term storage in environmental remediation and biosensing.

Unlocking the potential of Algerian lignocellulosic biomass: exploring indigenous microbial diversity for enhanced enzyme and sugar production

Nowadays, natural resources like lignocellulosic biomass are gaining more and more attention. This study was conducted to analyse chemical composition of dried and ground samples (500 μm) of various Algerian bioresources including alfa stems (AS), dry palms (DP), olive pomace (OP), pinecones (PC), and tomato waste (TW). AS exhibited the lowest lignin content (3.60 ± 0.60%), but the highest cellulose (58.30 ± 2.06%), and hemicellulose (20.00 ± 3.07%) levels. DP, OP, and PC had around 30% cellulose, and 10% hemicellulose. OP had the highest lignin content (29.00 ± 6.40%), while TW contained (15.70 ± 2.67% cellulose, 13.70 ± 0.002% hemicellulose, and 17.90 ± 4.00% lignin). Among 91 isolated microorganisms, nine were selected for cellulase, xylanase, and/or laccase production. The ability of Bacillus mojavensis to produce laccase and cellulase, as well as B. safensis to produce cellulase and xylanase, is being reported for the first time. In submerged conditions, TW was the most suitable substrate for enzyme production. In this conditions, T. versicolor K1 was the only strain able to produce laccase (4,170 ± 556 U/L). Additionally, Coniocheata hoffmannii P4 exhibited the highest cellulase activity (907.62 ± 26.22 U/L), and B. mojavensis Y3 the highest xylanase activity (612.73 ± 12.73 U/L). T. versicolor K1 culture showed reducing sugars accumulation of 18.87% compared to initial concentrations. Sucrose was the predominant sugar detected by HPLC analysis (13.44 ± 0.02 g/L). Our findings suggest that T. versicolor K1 holds promise for laccase production, while TW represents a suitable substrate for sucrose production.

Effective adsorption of As(V) from aqueous solution by quaternary ammonium and Zn2+ decorated lignin-based sorbent

Arsenic poses a serious harm to the natural environment and human health. Lignin decorated with quaternary ammonium and metal ion can effectively adsorb arsenic from aqueous solution. Zn2+/quaternary ammonium lignin was synthesized by quaternization and metallization from lignin with 3-Chloro-2-hydroxypropyl trimethylammonium chloride and ZnCl2. The morphology, functional groups and chemical compositions of adsorbent were identified by SEM-EDS, FTIR and XRD. The effects such as pH, initial As(V) concentration, contact time and adsorbent dosage on the adsorption capacity were investigated in batch system. The adsorption mechanism was explored by SEM-EDS, FTIR and XPS. It was shown that the adsorbent was rough and contained a large amount of quaternary ammonium and Zn2+. Zn2+/quaternary ammonium lignin exhibited much strong affinity towards As(V) with the maximum adsorption capacity of 70.38 mg·g-1 at 25 °C, oscillation rate of 180 r·min-1, pH of 5, initial As(V) concentration of 100 mg·L-1, contact time of 30 min and 1 g·L-1 Zn2+/quaternary ammonium lignin. The adsorption could be well described by Langmuir model and quasi-second-order kinetic model, indicating the monolayer homogeneous chemisorption nature. As(V) was adsorbed through electrostatic attraction of Zn2+ and ion exchange between H2AsO4- and Cl-.

Ultra-sensitive photoelectrochemical sensor for copper ion detection based on ITO/BiVO4 photoelectrode

In this work, a photoelectrochemical sensor for Cu2+ trace detection was prepared based on the excellent semiconductor material BiVO4 modified ITO electrode. It was found that Cu2+ formed a doping effect by adsorption on the surface of ITO/BiVO4 electrode, which inhibited the photogenerated electron complex and thus caused an increase in photocurrent. In addition, due to the complexation effect of EDTA on Cu2+, the Cu2+ adsorbed on the electrode surface is desorbed and the photocurrent returns to the blank value, making it possible to reuse electrodes. Under optimal conditions, the linearity range was measured between 0.1 pM and 0.1 μM and the detection limit was 0.063 pM. The PEC sensor exhibits the advantages of high sensitivity and reusability for Cu2+ detection. This provides a novel PEC detection platform for Cu2+ monitoring in environmental water samples.

Adsorption of methyl orange from aqueous solution with lignin-modified metal-organic frameworks: Selective adsorption and high adsorption capacity

The lignin-based metal-organic framework (UIO-g-NL) was prepared by a Schiff base reaction of aminated lignin and the zirconium cluster-based MOF (UIO-66-NH2) as an adsorbent of methyl orange (MO). The results showed that UIO-g-NL maintained the original crystal structure and aminated lignin was successfully introduced after functionalization. UIO-g-NL selectively adsorbed MO from a mixed solution 50 mg/L MO and 50 mg/L methylene blue (MB), with an adsorption efficiency of nearly 100%. In a mixed solution 250 mg/L MB and 250 mg/L MO, UIO-g-NL adsorbed both dyes with 1120.70 mg/g for MB and 961.54 mg/g for MO. Hydrogen bonding, π-π and NH-π interactions, and electrostatic attraction contribute to the MO adsorption by UIO-g-NL. In the MO/MB mixture, MO adsorption by UIO-g-NL follows the pseudo-second-order kinetic and Freundlich isotherm models, which is an endothermic, spontaneous, and feasible adsorption process. Furthermore, the MO adsorption efficiency of UIO-g-NL remained high (>90%) after six re-use cycles.

High efficient adsorption of W(VI) with a novel lignin-based biosorbent functionalized with Zn2+ and polyamine

Functionalized lignin-based biosorbent has become popular in wastewater treatment and extraction of valuable metals. Amination and metallization modification can effectively improve the adsorption performance of adsorbent. Zn2+/polyamine lignin for adsorption of W(VI) was synthesized by quaternization, amination and metallization from lignin with 3-chloro-2-hydroxypropyl trimethylammonium chloride, tetraethylenepentamine and ZnCl2. The adsorbent was characterized by SEM-EDS, FTIR and XRD. The adsorption performance of Zn2+/polyamine lignin for W(VI) was investigated in batch system. The adsorption mechanism was revealed by zeta potential, SEM-EDS and FTIR and XPS. It was shown that Zn2+/polyamine lignin exhibited great adsorption capacity at pH of 2, 25 °C, oscillation rate of 400 r/min, initial tungsten concentration of 700 mg·L-1 and adsorption time of 720 min. The maximum adsorption capacity of 0.5 g·L-1 Zn2+/polyamine lignin for W(VI) reached 488.28 mg·g-1. The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. W(VI) was adsorbed through electrostatic attraction of hydrogen bond and Zn2+, ion exchange with Cl- and coordination with -NH2. The adsorption capacity reduced by only 6.47 % after seven cycles of adsorption-desorption, which indicated that Zn2+/polyamine lignin had a great application prospect.

Diazo-reaction based dual-mode colorimetric-electrochemical sensing of nitrite in pickled food

Development of an effective and convenient sensor for sensitive detection of nitrites is of great concern since excessive amounts of nitrites can be harmful to both human health and the environment. In this work, Cu-MOF modified exfoliated graphite paper (EGP) was employed as a signal reporter to enable the visual and electrochemical dual-mode sensing of nitrites. Cu-MOFs were in situ synthesized on EGP, which exhibited an excellent oxidase enzyme-like activity to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidation product (oxTMB). The multi-layer structure and the superior electrical conductivity of EGP not only facilitated the loading of the Cu-MOF nanozyme for colorimetric sensing but also enabled its use as an underlying backbone to support electroanalysis. Based on the recognition of nitrite through a highly specific diazo reaction between nitrite and oxTMB, the addition of nitrite caused the colorimetric sensing solution to change color from blue to green, which allowed for the colorimetric sensing of nitrite with a limit of detection (LOD) of 8.5 × 10-6 mol L-1. Meanwhile, the Cu-MOF/EGP electrochemical platform was employed for ratiometric detection of nitrite based on the electrochemical oxidation of nitrite and TMB. Compared with the colorimetric mode, the electrochemical mode possessed higher sensitivity with a LOD of 5.4 × 10-7 mol L-1, indicating the high sensitivity and accuracy of the proposed dual-mode sensing strategy. Furthermore, the determination of nitrite in different pickled food samples is demonstrated.