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This study presents the fabrication of nanocomposite for the sequestering of Cr(VI) from solution. The nanocomposites were obtained from the molecular sieve and functionalized multiwall carbon nanotubes and further modified with Pentaclethra macrophylla (oil bean tree) stem bark extract. The pristine molecular sieve (MS) and the modified nanocomposite [Pentaclethra macrophylla stem bark extract anchored on molecular sieve (SMP)] adsorbent were characterized by the FTIR, FESEM, XRD, BET, and TGA techniques. The batch adsorption experiment revealed an agitation time of 120 min, 0.02 g dosage, and sorbate pH of 2.0 as optimum conditions for effective use of MS and SMP. Under these conditions a maximum monolayer capacity (qmax) of 135.5 mg g���1 was obtained for SMP, a value that is better compared to many other related absorbent materials. The uptake of Cr(VI) onto MS and SMP was best described by pseudo-first-order and Elovich kinetic models respectively. Meanwhile, the Freundlich model was noticed to sufficiently describe the isotherm data obtained for MS and SMP. The adsorption of Cr(VI) onto MS and SMP was spontaneous, endothermic, and entropy-driven. The reusability of the nanocomposite and its efficient Cr(VI) removal, present SMP as a potent adsorbent for the sequestration Cr(VI) from aqueous solution. nsufficient innovative research on the sequestration of Cr(VI) from the aquatic ecosystem has made Cr(VI) a recalcitrant water contaminant that often affects water sources. In this work, a novel plant anchor-nanocomposite was fabricated from the spent molecular sieve, multi-walled carbon nanotubes, and the extract from the stem bark of Pentaclethra macrophylla. It was envisaged that due to the phytochemical constituent of the modifier, this nanocomposite could also act as potent adsorbents for the treatment of Cr(VI) polluted water. To the best of our knowledge, the application of Pentaclethra macrophylla stem bark extract as a modifier for the green fabrication of nanocomposite has not been reported. The resulting composites showed good uptake capacity for Cr(VI) as well as efficient reusability.

In this research, the mechanism and efficiency of Cr(VI) uptake onto Irvingia gabonensis stem bark extract modified silica gel (IGMS) was reported for the first time. The pristine silica gel (PS) and IGMS adsorbents were characterized by the XRD, FTIR, FESEM, EDX, BET, and TGA techniques. The characterizations proved the successful coating of the plant extract onto silica gel. The FTIR spectra showed the Si–O–Si bands present on the silica gel materials. The FESEM revealed an increase in surface roughness of IGMS after coating with the plant extract, while TGA showed a high thermal stability of both PS and IGMS with over 65% of the initial weight retained at 800 °C. The batch Cr(VI) adsorption revealed optimum uptake at pH 2.0, with a maximum monolayer uptake capacity of 23.26–26.18 mg/g for IGMS at temperatures of 295 to 318 K. The kinetic modeling of Cr(VI) uptake onto PS and IGMS was best fitted by the Elovich model in comparison to the pseudo-second-order, pseudo-first-order, and intraparticle diffusion model. The Langmuir and Freundlich isotherms gave the best fit to the adsorption of Cr(VI) onto IGMS and PS, respectively. Adsorption thermodynamics revealed endothermic, increased randomness and spontaneous removal of Cr(VI) onto IGMS and PS adsorbents. The results revealed that Irvingia gabonensis stem bark extract modified silica gel is a viable and highly efficient adsorbent for the removal of Cr(VI) from Cr(VI)-contaminated effluents.

Multiwalled carbon nanotubes/quartzite nanocomposite modified with the extract of Dacryodes edulis leaves was synthesized and designated as Q, which was applied for the removal of Cr(VI) from water. The adsorbents (PQ and Q) were characterized using the SEM, EDX, FTIR, TGA, XRD, and BET analyses. The XRD revealed the crystalline composition of the nanocomposite while the TGA indicated the incorporated extract as the primary component that degraded with an increase in temperature. The implication of the modifier was noticed to enhance the adsorption capacity of Q for Cr(VI) by the introduction of chemical functional groups. Optimum Cr(VI) removal was noticed at a pH of 2.0, adsorbent dose (50 mg), initial concentration (100 mg dm−3), and contact time (180 min). The kinetic adsorption data for both adsorbents was noticed to fit well to the pseudo-second-order model. The adsorption equilibrium data were best described by the Langmuir model. The uptake of Cr(VI) onto PQ and Q was feasible, endothermic (ΔH: PQ = 1.194 kJ mol−1 and Q = 34.64 kJ mol−1) and entropy-driven (ΔS : PQ = 64.89 J K−1 mol−1 and q = 189.7 J K−1 mol−1). Hence, the nanocomposite demonstrated potential for robust capacity to trap Cr(VI) from aqueous solution.

Nanocrystalline cellulose (NCC) was used as a dual reducing- and stabilizing agent in the production of silver nanoparticles (AgNPs), and addition of Stӧber silica (SiO2) provided an efficient support. The silica was prepared by a sol-gel method, the added NCC confined the AgNPs and added stability. The formed AgNPs/SiO2/NCC nanocomposite was evaluated as a substrate for surface-enhanced Raman scattering (SERS) of the fungicide and pesticide malachite green (MG) and the results were compared with the corresponding silica-free AgNPs/NCC material. A UV–vis peak for AgNPs/SiO2/NCC was broad with a shoulder at 490 nm, which we ascribe to the phenomena of plasmonic nanoparticle clustering. TEM micrographs showed that the plasmonic nanoparticles were monodispersed with a mean diameter of 19.5 nm in AgNPs/NCC while they aggregated into clusters on SiO2 in AgNPs/SiO2/NCC resulting in approximately 20 nm increase in mean diameter of the SiO2. The SERS performance of the composite material was evaluated by using MG as a probe and showed AgNPs/SiO2/NCC as a superior sensory substrate due to the silica clustering which is directly related to an increased formation “hot spot” zones leading to a significant amplification of SERS signals observed as higher intensities of Raman peaks of MG. SERS substrate of silver nanoclusters with net negative surface charge detected MG. The improved “hot spot” signal detection led to high sensitivity with a limit of detection (LOD) of 0.9 nM while AgNPs/NCC showed LOD of 5.2 nM, based on a signal to background ratio of 3:1. This result underscores the huge but under-appreciated contribution of SERS “hot spots” as AgNPs assembled into clusters in contrast to monodispersed AgNPs in the absence of SiO2.

Nanocrystalline cellulose (NCC) was isolated from discarded cigarette filter (DCF) and used in the dual role of reducing- and stabilizing agent in the formation of silver nanoparticles (AgNPs). By this method, a notable size variation of the synthesized AgNPs was found over the pH range 5–10, ranging from 4.61 nm at pH = 9 increasing to 19.93 nm diameter at pH = 5. The size and yield of the AgNPs were also affected by reaction time and concentration. The spherically shaped AgNPs induced a localized surface plasmon resonance (LSPR) around 416 nm. The Ag content in dry AgNPs was 81.9 wt%, which correlated with 82.1 wt% mass left at 600 °C. Further analysis showed that the dry AgNPs were macroporous with reduced surface area and porosity upon calcination. The sensitivity of the AgNPs colloids showed excellent surface-enhanced Raman scattering (SERS) of riboflavin. The limit-of-detection (LOD) for riboflavin based on a signal to background ratio of 3:1 was found to be 3 × 10−7 M. The intensities of SERS signals increased with increase in concentration.

Two Schiff bases, (E)-1-(4-methoxyphenyl)-N-((E)-3-(4-nitrophenyl)allylidene)methanamine (compound 1) and (E)-N-((E)-3-(4-nitrophenyl)allylidene)-2-phenylethanamine (compound 2) have been synthesized and characterized using spectroscopic methods; time of flight MS, 1H and 13C NMR, FT-IR, UV–VIS, photoluminescence and crystallographic methods. The structural and electronic properties of compounds 1 and 2 in the ground state were also examined using the DFT/B3LYP functional and 6-31 + G(d,p) basis set, while the electronic transitions for excited state calculations were carried out using the TD-DFT/6-31 + G(d,p) method. The Schiff base compounds, 1 and 2 crystallized in a monoclinic crystal system and the P21/c space group. The emission spectra of the compounds are attributed to conjugated π-bond interaction while the influence of the intra-ligand charge transfer resulted in a broad shoulder for 1 and a double emission peak for 2. The calculated transitions at 450 and 369 nm for 1 and 2 respectively are in reasonable agreement with the experimental results. The higher values of dipole moment, linear polarizability and first hyperpolarizability of 1, suggest a better optical property and better candidate for the development of nonlinear optical (NLO) materials.

Owing to the common phenomenon of cyanide toxicity, this study focused on oxidative catalytic detoxification of aqueous cyanide in the presence of copper-crown chitosan nanofiber. To overcome the difficulty in electrospinning chitosan, chitosan-salicylaldehyde was initially synthesized via Schiff base condensation, electrospun, and post neutralised into chitosan nanofiber. The copper-crown nanofiber was prepared using the impregnation method. The nanofiber material was characterized using FT-IR, SEM, TGA and DSC. The observed pseudo first-order rate constant for the catalytic H2O2 oxidation of aqeous cyanide with copper-crown nanofiber as catalyst was found to be 16 times greater than the oxidation with only copper catalyst. In addition, the reaction was found to be dependent on the size of the copper-crown nanofiber, pH, temperature, and H2O2/CN-. The reusability of the copper-crown nanofiber catalyst makes the process economically and potentially viable for commercial application.

This study investigates the capacity of spent self-indicating silica gels modified with Harpephyllumcaffrum(wild plum) stem bark extract to remove hexavalent chromium from wastewater. The physicochemical properties of the adsorbents were assessed using FESEM, FTIR, PXRD, TGA and BET surface analyser. The batch adsorption technique was used to examine the capacity of spent self-indicating silica gel (SIPP) and modified spent self-indicating silica gel (SIP) to eliminate Cr(VI) from the aqueous solution. The uptake capacity of the sorbents was noticed to increase with increasing adsorbent dose, contact time and initial concentration of Cr(VI). On the contrary, the potential of SIPP and SIP were observed to decline with increasing solution pH, similarly as found for most Cr(VI) absorbents. However, the uptake capacity of the SIPP and SIP were noticed to be optimum at 0.05 g adsorbent dosage and 180 min contact time. Meanwhile, the kinetic behaviour of SIPP and SIP in the removal of Cr(VI) was best described by the Elovich kinetic model. Furthermore, the uptake of Cr(VI) onto SIP and SIPP was sufficiently described by the three-parameter isotherm Sips and Freundlich isotherms respectively. The Cr(VI) adsorption was endothermic, entropy-driven, and feasible. The application of Harpephyllum caffrumstem bark extract on SIPP as Cr(VI) adsorbent was significant and the reusability of the adsorbent portrayed the capacity of SIP to adapt to a full-scale wastewater treatment practice.

Aluminium oxide (ALU) and carbon-coated aluminium oxide modified with Kigelia africana leaf extract (KECA) were employed for the removal of toxic hexavalent chromium (Cr(VI)) from the aqueous phase. The adsorbents (ALU and KECA) were characterized by TGA, BET, FESEM, FTIR, Raman and XRD spectroscopic techniques. The potential of KECA and ALU to remove Cr(VI) from simulated wastewater was optimum at pH 2, sorbent dose of 0.025 g and a contact time of 200 min. Meanwhile, the uptake capacity of KECA and ALU was enhanced with an increase in sorbent dose, contact time and initial Cr(VI) concentration. The uptake of Cr(VI) onto the adsorbents ALU and KECA was kinetically best described by the pseudo-second-order and Elovich models, respectively. Besides, the equilibrium data acquired for ALU and KECA obeyed Freundlich and Langmuir isotherm models, respectively. ALU and KECA were observed to have optimum adsorption capacity of 56.45 mg g−1 and 258.2 mg g−1, respectively. The adsorption of Cr(VI) onto the adsorbents was thermodynamically feasible, endothermic in nature and entropy-driven. A decrease in efficiency was observed on regeneration of the absorbents, thus limiting their reusability. However, the presence of functional groups with reducing property in the extract of Kigelia africana leaves was noticed to enhance the capacity of the adsorbent to abstract Cr(VI) from the solution. Hence, this study demonstrates the potential of KECA to sequestrate Cr(VI) from an aqueous solution and provides a reference for its application to the treatment of Cr(VI)-laden industrial wastewater.

The utilization of fibrous prunus dulcis seed shell powder (UPDSSP) and the phosphate-modified derivative (P-MPDSS) for the abstraction of Pb2+ was tested. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray (EDX), and the physicochemical characterizations revealed desirable characteristics of the adsorbents for efficient Pb(II) uptake. The FTIR of UPDSSP and P-MPDSS showed several functionality groups on the adsorbents. SEM morphology revealed high porosity surface structure of both adsorbents, while BET measurements showed an increase in surface area from 5.84 m2/g to 11.32 m2/g after phosphate modification. The modified adsorbent showed higher Pb(II) uptake than UPDSSP at variations of temperature, time, pH, metal concentration, and material dosage. pH 5.0 was optimum for Pb(II) adsorption and equilibrium was reached at 90 min on UPDSSP and P-MPDSS. The Freundlich isotherm presented the best fit (R2 > 0.991) than the Langmuir and Dubinin-Raduskkevich models. The pseudo-second-order gave the best fit (R2 > 0.971) than the pseudo-first-order and intraparticle diffusion kinetic equations. Thermodynamics showed endothermic, spontaneous, and physical adsorption of Pb(II) ions onto the adsorbents. The adsorbents showed good potentials for regeneration and reuse. The results revealed UPDSSP and P-MPDSS as viable materials for the decontamination of Pb polluted water.

Melon seed shells (MSS) are a hazard to the environment as they host disease vectors. To alleviate the effect, we explored melon seed shells (MSS) as a new source of nanocrystalline cellulose (NCC) with reducing- and stabilizing capacity for the synthesis of silver nanoparticles (AgNPs). The isolation of NCC from discarded MSS served the dual purpose of a reducing- and stabilizing agent in the synthesis of AgNPs. The isolated needle-like crystals (MSS-NCC) had a mean length 204 nm, width 7 nm and aspect ratio 30. The NCC had crystallinity index of 94% with surface rich in –OH and –COOH functionality. The obtained AgNPs covered the surface of the MSS-NCC and catalysed the reduction of nitrobenzene to aniline using NaBH4. The process of the reduction monitored via UV-vis spectroscopy was completed within 12 min. with a rate constant 0.04 min−1 as revealed by the kinetic study.

We report the isolation of nanocrystalline cellulose (NCC) produced from discarded cigarette filters (DCF). The DCF were processed into cellulose via ethanolic extraction, hypochlorite bleaching, alkaline deacetylation, and then converted into NCC by sulfuric acid hydrolysis. The morphological structures of the isolated NCC established with TEM showed that the nanocrystals were needle-like with a mean length of 143nm. FEGSEM showed the morphological transition of the micro-sized DCF to self-assembled NCC while EDX revealed the presence of Ti (as TiO2) in DCF, which was retained in the NCC. A NCC sample was freeze-dried and showed a specific surface area of 7.78m2/g. The crystallinity of the NCC film and freeze-dried samples were 96.77% and 94.47%, respectively. Crystallite sizes of the freeze-dried (8.4nm) and film (7.6nm) samples correlated with the mean width (8.3nm) of the NCC observed under TEM.

Alternanthera pungens Kunth commonly called khaki weed is from the family Amaranthaceae. It is a herbaceous perennial plant that has stems prostrate, rarely rising and about 10-50 cm long. The work was carried out due to the scarcity of information on the volatile constituents from the plant leaves despite works on the flower and other parts. The extraction of the essential oils from the dried leaves was carried out by the hydro distillation method using an all-glass Clevenger apparatus. The extracted oils were then analyzed using gas chromatography-mass spectrometry (GC-MS). A total of twelve constituents' representing 93.39% of A. Pungens oil with a yield of 0.4% (v/w) was obtained. The analysis of the GC-MS results of the leaf oil showed that it was dominated by â-ionone (42.18%) and hexahydrofarnesyl acetone (15.53%), others in trace amounts include; methyl palmitate (6.13%), 1octadecyne (4.72%), undecane (3.73%), para-mentha-1, 3, 8-triene (3.65%), isophytol (3.21%), ?cadinene (3.06%), 1, 2-dimethyl cyclooctene (3.05%), para-cymene (2.96%), phytol (2.67%) and neophytadiene (2.50%). The common classes of compounds present in the leaves oil are aceto monocyclic monoterpenoid (42.18%), sesquiterpenoids (18.59%), hydrocarbons (11.50%), diterpenoids (8.38%), monoterpenes (6.61%) and fatty acids (6.13%).The constituents and the compositional pattern of essential oil identified from the leaves of Alternanthera pungens grown in Nigeria differ quantitatively and qualitatively from previously reported member of the genus and the presence of sesquiterpenoid as one of the major components of the oils justify the traditional use of the plants in treating pains, headaches and inflammations.