Heavy metal sequestration from wastewater by metal-organic frameworks: a state-of-the-art review of recent progress.

Metal-organic frameworks (MOFs) have emerged as highly promising adsorbents for removing heavy metals from wastewater due to their tunable structures, high surface areas, and exceptional adsorption capacities. This review meticulously examines and summarizes recent advancements in producing and utilizing MOF-based adsorbents for sequestering heavy metal ions from water. It begins by outlining and contrasting commonly employed methods for synthesizing MOFs, such as solvothermal, microwave, electrochemical, ultrasonic, and mechanochemical. Rather than delving into the specifics of adsorption process parameters, the focus shifts to analyzing the adsorption capabilities and underlying mechanisms against critical metal(loid) ions like chromium, arsenic, lead, cadmium, and mercury under various environmental conditions. Additionally, this article discusses strategies to optimize MOF performance, scale-up production, and address environmental implications. The comprehensive review aims to enhance the understanding of MOF-based adsorption for heavy metal remediation and stimulate further research in this critical field. In brief, this review article presents a comprehensive overview of the contemporary information on MOFs as an effective adsorbent and the challenges being faced by these adsorbents for heavy metal mitigation (including stability, cost, environmental issues, and optimization), targeting to develop a vital reference for future MOF research.

Amine-Decorated Methacrylic Acid-based Inverse Vulcanized Polysulfide for Effective Mercury Removal from Wastewater.

Mercury [Hg(II)] contamination is an indefatigable global hazard that causes severe permanent damage to human health. Extensive research has been carried out to produce mercury adsorbents; however, they still face certain challenges, limiting their upscaling. Herein, we report the synthesis of a novel amine-impregnated inverse vulcanized copolymer for effective mercury removal. Poly(S-MA) was prepared using sulfur and methacrylic acid employing the inverse vulcanization method, followed by functionalization. The polyethylenimine (PEI) was impregnated on poly(S-MA) to increase the adsorption active sites. The adsorbent was then characterized byusing Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). FTIR spectroscopy confirmed the formation of the copolymer, and successful impregnation of PEI and SEM revealed the composite porous morphology of the copolymer. Amine-impregnated copolymer [amine@poly(S-MA)] outperformed poly(S-MA) in mercury as it showed 20% superior performance with 44.7 mg/g of mercury adsorption capacity. The adsorption data best fit the pseudo-second-order, indicating that chemisorption is the most effective mechanism, in this case, indicating the involvement of NH2 in mercury removal. The adsorption is mainly a monolayer on a homogeneous surface as indicated by the 0.76 value of Redlich-Peterson exponent (g), which describes the adsorption nature advent from the R2 value of 0.99.

Synthesis and performance evaluation of slow-release fertilizers produced from inverse vulcanized copolymers obtained from industrial waste.

To improve crop nutrient uptake efficacy (NUE) and better manage fertilization, slow-release fertilizers (SRFs) are developed by either coating the urea granules or making a composite. Several materials have already been developed, nevertheless, scalability of those materials is still a challenge due to their inherit drawbacks (such as hydrophilicity, crystallinity, non-biodegradability, etc.). Herein, we utilized a biodegradable, green and sustainable copolymer produced from industrial waste (sulfur-petroleum industry waste and myrcene-citrus industry waste) to coat the urea using a facile coating method to develop novel SRFs and achieve better agronomic and environmental advantages. The copolymer was first synthesized using a facile, solvent-free one-pot method called inverse vulcanization followed by Fourier transform infrared spectroscopy (FTIR) analysis to confirm the successful reaction between myrcene and sulfur subsequently coating the copolymer on urea granule. The morphology and coating thickness of coated fertilizers were analysed using scanning electron microscopy (SEM), followed by a nitrogen release test in distilled water and a soil burial test to confirm the biodegradability. The nitrogen release test revealed that the SRF with the maximum coating thickness of 1733 µm releases only 16% of its total nitrogen after 4 days of incubation compared to the pristine urea which releases all its nutrient within 1 day. The soil burial test confirms the biodegradability of the copolymer, as after 50 days of incubation in soil the copolymer loses almost 18.25% of its total weight indicating that the copolymer is degrading.

Sulfur enriched slow-release coated urea produced from inverse vulcanized copolymer.

Slow-release fertilizers are developed to enhance the nutrient use efficiency (NUE), by coating urea with less water soluble or hydrophobic material. Diverse range of materials have been utilized to coat urea, however, their inherit non-biodegradability, hydrophilicity, crystallinity, and high synthesis cost limits their scalability. Herein, we reported the preparation of a novel slow-release sulfur enriched urea fertilizers using sustainable hydrophobic, biodegradable, crosslinked copolymer made from sulfur and rubber seed oil (Poly(S-RSO)) through the use of dip coating method. Scanning electron microscopy (SEM) was employed to study the fertilizers morphology and estimate the coating film thickness. A nitrogen release test was carried out in distilled water, which revealed that the coated fertilizers with a coating thickness of 165 µm, 254 µm and 264 µm released only 65 % of its total nutrient content after 2, 19 and 43 days of incubation, respectively: hence, showing an excellent slow-release property. In soil, fertilizer with 264 µm coating thickness released only 17 % nitrogen after 20 days of incubation, in line with the European standard (EN 13266, 2001). The release kinetic data best fits the Ritger-Peppas model with a R2 value of 0.99 and the n value of 0.65 indicated the release was mainly due to diffusion. Submerged cultivation (SmC) demonstrated the potential of poly(S-RSO) to enhance sulfur oxidation; it was observed that the copolymer oxidation was 50 % greater than that of elemental sulfur. A comparison between the newly developed fertilizers and existing coated fertilizers was also presented. On the whole, the results demonstrated outstanding slow-release characteristics and improved sulfur oxidation.

A Degradable Inverse Vulcanized Copolymer as a Coating Material for Urea Produced under Optimized Conditions.

Global enhancement of crop yield is achieved using chemical fertilizers; however, agro-economy is affected due to poor nutrient uptake efficacy (NUE), which also causes environmental pollution. Encapsulating urea granules with hydrophobic material can be one solution. Additionally, the inverse vulcanized copolymer obtained from vegetable oils are a new class of green sulfur-enriched polymer with good biodegradation and better sulfur oxidation potential, but they possess unreacted sulfur, which leads to void generations. In this study, inverse vulcanization reaction conditions to minimize the amount of unreacted sulfur through response surface methodology (RSM) is optimized. The copolymer obtained was then characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR confirmed the formation of the copolymer, TGA demonstrated that copolymer is thermally stable up to 200 °C temperature, and DSC revealed the sulfur conversion of 82.2% (predicted conversion of 82.37%), which shows the goodness of the model developed to predict the sulfur conversion. To further maximize the sulfur conversion, 5 wt% diisopropenyl benzene (DIB) as a crosslinker is added during synthesis to produce terpolymer. The urea granule is then coated using terpolymer, and the nutrient release longevity of the coated urea is tested in distilled water, which revealed that only 65% of its total nutrient is released after 40 days of incubation. The soil burial of the terpolymer demonstrated its biodegradability, as 26% weight loss happens in 52 days of incubation. Thus, inverse vulcanized terpolymer as a coating material for urea demonstrated far better nutrient release longevity compared with other biopolymers with improved biodegradation; moreover, these copolymers also have potential to improve sulfur oxidation.

Multivariate Analysis Coupled with M-SVM Classification for Lard Adulteration Detection in Meat Mixtures of Beef, Lamb, and Chicken Using FTIR Spectroscopy.

Adulteration of meat products is a delicate issue for people around the globe. The mixing of lard in meat causes a significant problem for end users who are sensitive to halal meat consumption. Due to the highly similar lipid profiles of meat species, the identification of adulteration becomes more difficult. Therefore, a comprehensive spectral detailing of meat species is required, which can boost the adulteration detection process. The experiment was conducted by distributing samples labeled as "Pure (80 samples)" and "Adulterated (90 samples)". Lard was mixed with the ratio of 10-50% v/v with beef, lamb, and chicken samples to obtain adulterated samples. Functional groups were discovered for pure pork, and two regions of difference (RoD) at wavenumbers 1700-1800 cm-1 and 2800-3000 cm-1 were identified using absorbance values from the FTIR spectrum for all samples. The principal component analysis (PCA) described the studied adulteration using three principal components with an explained variance of 97.31%. The multiclass support vector machine (M-SVM) was trained to identify the sample class values as pure and adulterated clusters. The acquired overall classification accuracy for a cluster of pure samples was 81.25%, whereas when the adulteration ratio was above 10%, 71.21% overall accuracy was achieved for a group of adulterated samples. Beef and lamb samples for both adulterated and pure classes had the highest classification accuracy value of 85%, whereas chicken had the lowest value of 78% for each category. This paper introduces a comprehensive spectrum analysis for pure and adulterated samples of beef, chicken, lamb, and lard. Moreover, we present a rapid M-SVM model for an accurate classification of lard adulteration in different samples despite its low-level presence.