Biopolymer composites are known for their utility in diverse applications. In this paper, we report an effective methodology for the detoxification of chromium using cellulose-montmorillonite composite material as the adsorbent. The interaction of surfactant modified sodium montmorillonite (NaMMT) with cellulose biopolymer is followed by the subsequent adsorption of Cr(VI) from aqueous solution as bichromate anion onto the surface of the biocomposite material. The composite adsorbent was characterized comprehensively using Fourier transform infrared spectroscopy (FT-IR), Energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD) and Branauer-Emmett-Teller (BET) isotherm studies. The material exhibited a maximum adsorption capacity of 22.2 mg g–1 in accordance with the Langmuir isotherm model. The mesoporous nature of the material was ascertained from the nitrogen adsorption isotherm study and the adsorption process was in accordance with second order kinetics. The spontaneity of the adsorption process could be confirmed from the study of the adsorption thermodynamics. The composite material could be regenerated using sodium hydroxide as the eluent. The adsorbent could be reused with quantitative recovery for 10 adsorption–desorption cycles. An aqueous phase feed volume of 400 mL could be quantitatively treated by column method at 100 mg L–1 concentration of Cr(VI) with a preconcentration factor of 50. The applicability of the method is demonstrated in the quantitative removal of total chromium from a chrome tannery effluent sample.

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We report an interesting interaction between oxidized multiwalled carbon nanotubes (oxi-MWCNTs), tetra n-heptylammonium bromide (ionic liquid) and Cr(vi)/Cr(iii).

Graphite-like graphitic carbon nitride (g-C 3 N 4 ) has gained considerable interest in the past few years. However, merely a few studies have been undertaken regarding the application of g-C 3 N 4 for metal adsorption and visible-lightdriven reduction of aromatic nitro compounds. Here, we describe a versatile method for the preparation of g-C 3 N 4 nanocomposite decorated with magnetite nanoparticles (g-C 3 N 4 @Fe 3 O 4 NPs) that subsequently showed their efficiency in sequestration of Cr(VI)/Cr(III) and NaBH 4 -mediated conversion of 2-nitroaniline (2-NA) and 4-nitroaniline (4-NA) under visible-light exposure. The as-synthesized g-C 3 N 4 @Fe 3 O 4 NPs adsorbent revealed excellent water dispersibility, superior magnetic property, and porous structure. Numerous surface hydroxyls (−OH) and amino groups (−N, −NH, −NH 2 ) enabled g-C 3 N 4 @Fe 3 O 4 NPs to rapidly isolate Cr(VI) from aqueous solution through applying an outer magnetic field. The adsorbed Cr(VI) on the g-C 3 N 4 @Fe 3 O 4 NPs surface offered a maximum equilibrium adsorption capacity of 555 mg g −1 , and their absorption behavior followed the Langmuir isotherm and pseudo-second-order kinetics model. The morphology, surface properties, crystalline structure, and chemical compositions of g-C 3 N 4 @Fe 3 O 4 NPs were thoroughly investigated. In real-world applications, g-C 3 N 4 @Fe 3 O 4 NPs was implemented for the determination of total chromium in industrial soil sludge samples. Additionally, NaBH 4 -induced reduction of 2-NA to 2-aminoaniline and 4-NA to 4-aminoaniline catalyzed by g-C 3 N 4 @ Fe 3 O 4 NPs (catalyst loading as low as 20 mg) was achieved within 8 min.

The universal concern for heavy metal removal demands effective methods for detoxification. Chromium(VI) is one such heavy metal which is recognized to be carcinogenic. In this paper, an efficient approach is proposed for the removal of chromium based on the impregnation of trioctylamine (TOA) on a macroporous Amberlite XAD-1180 polymeric matrix. Chromium(VI) could be quantitatively adsorbed in an acidic medium (pH 2 to 3), while chromium(III) could be retained on the resin matrix at alkaline pH. The adsorbent was characterized using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) studies. The comprehensively characterized adsorbent showed a high adsorption capacity of 171.82 mg 3 g À1 in accordance with the Langmuir isotherm model. The adsorption follows second-order kinetics, and a study of the various thermodynamic parameters such as Gibbs energy, entropy, and the enthalpy changes showed that the adsorption decreases with an increase in temperature. Column studies and regeneration data validated the performance efficiency of the adsorbent with large sample volume tolerance (1 L) and high preconcentration factor (100). The resin column could be regenerated using NaOH after the removal of total chromium without any loss in the performance efficiency for nearly 15 cycles. Chromium could be effectively separated from a synthetic mixture of various ions, thus making it a viable proposition for the detoxification of chromium from industrial effluents.

Recently, two-dimensional transition metal dichalcogenides (TMDs) have received tremendous attention in many fields including environmental remediation. Magnetic nanoparticles (Fe 3 O 4 NPs) decorated with MoS 2 (MoS 2 @Fe 3 O 4 NPs) have been synthesized via a new one-step synthesis route and utilized as an efficient adsorbent for removal of Cr(VI)/Cr(III) from aqueous solutions. The obtained MoS 2 @Fe 3 O 4 NPs with numerous surface hydroxyl groups show uniform size and shape, excellent water-dispersibility, and superior magnetic property to enhance the adsorption. The physicochemical properties of the adsorbent prior to and after adsorption of Cr(VI)/Cr(III) were extensively characterized using several advanced instrumental techniques.The adsorption of Cr(VI)/Cr(III) on MoS 2 @Fe 3 O 4 NPs was performed under batch conditions aiming at identification of optimal contact time, pH value of chromium solution, and influence of the presence of competitive ions. This study was supported by modeling of adsorption equilibrium and kinetics by using empirical equations.

A novel aluminium oxy hydroxide [Al-O(OH)] modified graphene oxide was prepared by a chemical precipitation method wherein Al 3+ ions could interact effectively with the different functional groups of graphene oxide (GO). The prepared (GO-Al-O(OH) adsorbent was tested for the effective defluoridation of water. The Al 3+ modified graphene oxide adsorbent was characterized using FT-IR, FT-Raman, SEM-EDS, XRD and XPS studies. The thermodynamically feasible adsorption is supported by the pseudo second order kinetics and a high Langmuir maximum adsorption capacity (51.42 mg g À1 ) for the GO-Al-O(OH) adsorbent. Furthermore, we could treat 2.0 L of 5.0 mg L À1 fluoride ion solution to bring the level within the permissible limits and the regeneration of the adsorbent was done using ammonium hydroxide. Experimental details MaterialsGraphite with a mean particle size (<20 mm) was procured from Sigma Aldrich. Orthophosphoric acid (H 3 PO 4 , 85%), hydrogen peroxide (H 2 O 2 , 30%), potassium permanganate (KMnO 4 ), aluminum sulfate hydrate (Al 2 (SO 4 ) 3 $16H 2 O), sodium

Aggregation-induced emission enhancement (AIEE) of thiolated gold nanoclusters (AuNCs) has emerged as an attractive and alternative strategy to improve their brightness. This study demonstrates Ce(iii)-triggered AIEE of glutathione-capped AuNCs (GSH-AuNCs) through the coordination between two carboxylic groups of GSH and Ce(iii). The cluster size and valence state of GSH-AuNCs are almost identical to those of a Ce(iii)-induced assembly of GSH-AuNCs (named Ce(iii)-GSH-AuNCs). More importantly, the as-prepared Ce(iii)-GSH-AuNCs exhibit a higher quantum yield (up to 13%), longer luminescence lifetime, and shorter maximum luminescence peak than GSH-AuNCs. Additionally, Ce(iii)-GSH-AuNCs possess redox-switchable luminescence, high salt stability, and long-term storage stability. These findings provide clear evidence that the Ce(iii)-triggered aggregation of GSH-AuNCs is a crucial factor to improve the luminescence property of GSH-AuNCs. Intriguingly, the presence of adenosine triphosphate (ATP) switches off the luminescence of Ce(iii)-GSH AuNCs through the significant formation of Ce(iii)-ATP complexes. Furthermore, the ATP-induced luminescence quenching of Ce(iii)-GSH-AuNCs can be paired with the alkaline phosphatase (ALP)-ATP system to design a turn-on luminescent probe for ALP; the limit of detection for ALP is estimated to be 0.03 U L-1. Also, the biocompatibility of Ce(iii)-GSH-AuNCs enables the proposed system to detect ALP in human serum and HeLa cells.