Kinetics and Mechanism of Formation of 2,3-Disubstituted 1,4-Benzothiazines: One Pot DMSO Assisted Cyclocondensation of Bisanilino Disulphide and 1, 3-Dicarbonyls

The kinetics of DMSO (dimethylsulphoxide) assisted one pot cyclocondensation of bisanilino disulphide and 1,3-dicarbonyls has been investigated using spectral method. The kinetic measurements have been carried by varying media, temperature and concentration of the reactants. The assistance of DMSO is investigated. The order of reaction, effects of substituents with dicarbonyls on the rates and thermodynamic parameters has also been reported. First time reaction conditions are optimised for performing the cyclocondensation conveniently and rapidly. Probably mechanism has been proposed and order of reaction was determined on the basis of rate expression and was in agreement with second order rate equation, used for the determination of rate constants.

Adsorption of reactive blue 49 onto cross-linked chitosan-based composites containing waste mussel shell and waste active sludge char

Cross-linked chitosan/waste mussel shell (C/WMS) and chitosan/waste mussel shell/waste active sludge char (C/WMS/WASC) composites were prepared from waste mussel shell, waste active sludge (WAS), and chitosan, were cross-linked with glutaraldehyde. The quantities of chitosan, WMS, and WASC used for the C/WMS and C/WMS/WASC composites were 1:1 and 1:0.5:0.5, respectively. The two adsorbents were characterized their quality by a scanning electron microscope (SEM), an energy-dispersive X-ray spectroscopy (EDX), and a Brunauer, Emmett and Teller (BET) analyzer. The effects of contact time (0–1,620 mins), pH (1–5), adsorbent dosage (0.01–0.1 g/50 ml), initial dye concentration (20–100 mg/L), and temperature (25–45 °C) on Reactive Blue 49 (RB49) adsorption onto C/WMS and C/WMS/WASC composites were investigated. The maximum RB49 adsorption capacity of C/WMS and C/WMS/WASC composites were 54.7 and 38.8 mg/g, respectively. The experimental data were analyzed by kinetic and isotherm models. The Freundlich isotherm was a good fit for the experimental data of RB49 adsorption on C/WMS and C/WMS/WASC composites, and the adsorption kinetics for both adsorbents were the pseudo-second-order rate equation. All results showed the preparative adsorbents can be used as effective adsorbents for the treatment of waste water contaminated with RB49 since being low cost and eco-friendly for the environment.

Biodegradation of omethoate by Bacillus sp. YB-10: optimization of culture conditions and degradation characteristics

Omethoate is an acute organophosphorus pesticide which is widely used. It presents a high pollution potential and health risk nowadays. In this study, Bacillus sp. YB-10, which was isolated from the activated sludge of a pharmaceutical wastewater treatment plant, was used for degrading omethoate. The culture conditions and degradation characteristics were investigated. Results showed that the Bacillus sp. YB-10 could degrade omethoate through co-metabolism. The optimal carbon and nitrogen sources were glucose and NH4NO3, respectively. Response surface methodology (RSM) results showed that the most appropriate nutrition ratio of C:N:P was 3:1:1 when degrading 1,000 mg/L of omethoate. Omethoate degradation kinetics could be described by a first-order rate equation. The optimal degradation conditions were pH of 7.0, temperature of 30℃, initial bacteria concentration of 0.25%, rotation speed of 150 r/min. Under the optimal conditions, the degradation rate reached 77.24% within 5 d by the Bacillus sp. YB-10 when the initial omethoate concentration was 1,000 mg/L.

Study on Cecropin B2 Production via Construct Bearing Intein Oligopeptide Cleavage Variants

In this study, genetic engineering was applied to the overexpression of the antimicrobial peptide (AMP) cecropin B2 (cecB2). pTWIN1 vector with a chitin-binding domain (CBD) and an auto-cleavage Ssp DnaB intein (INT) was coupled to the cecB2 to form a fusion protein construct and expressed via Escherichia coli ER2566. The cecB2 was obtained via the INT cleavage reaction, which was highly related to its adjacent amino acids. Three oligopeptide cleavage variants (OCVs), i.e., GRA, CRA, and SRA, were used as the inserts located at the C-terminus of the INT to facilitate the cleavage reaction. SRA showed the most efficient performance in accelerating the INT self-cleavage reaction. In addition, in order to treat the INT as a biocatalyst, a first-order rate equation was applied to fit the INT cleavage reaction. A possible inference was proposed for the INT cleavage promotion with varied OCVs using a molecular dynamics (MD) simulation. The production and purification via the CBD-INT-SRA-cecB2 fusion protein resulted in a cecB2 yield of 58.7 mg/L with antimicrobial activity.

Facile Synthesis of Novel Carboxymethyl-Chitosan/Sodium Alginate Grafted with Amino-Carbamate Moiety/Bentonite Clay Composite for Effective Biosorption of Ni (II) from Aqueous Solution

In the present study, a novel biosorbent clay composite, based on carboxymethyl-chitosan/sodium alginate grafted with amino-carbamate moiety/bentonite clay (CA-CMC/Bt) was prepared. The produced sorbent was conditioned in the form of hydrogel beads by ionotropic gelation with Ca(II) ions, and thoroughly characterized using FTIR, XRF, XRD, SEM and zeta potential measurements. FTIR and SEM confirmed the successful grafting and intercalation of clay mineral into modified biopolymer. Hydrogel beads were observed to be very integrated and stable under a wide pH working range (from 2.0 to 12.0). CA-CMC/Bt was employed for adsorptive remediation of Ni(II) from aqueous media. Sorption process was found as a function of various parameters such as sorbent dosage, contact time, pH and initial concentration. Kinetic data could be well explained by pseudo second order rate equation (PSORE), suggesting that complexation or valence forces are playing significant role in the uptake of Ni(II) ions. Isothermal sorption data was analysed using different sorption models such as Langmuir, Freundlich and Sips. Data was well fitted with Langmuir and Sips model, maximum monolayer sorption capacity (qm) was calculated (by non-linear fitting of data) as 159 mg/g at 298 K and pH 5.5. Separation factor (RL) was found as 0 < RL < 1 which indicated favourable sorption. Thermodynamic parameters i.e. ΔGo, ΔHo and ΔSo were quantified and patterned the sorption process as exothermic, spontaneous with increase in system entropy. CA-CMC/Bt was found cost-effective, efficient and reusable material in Ni(II) competitive recovery.

A comparative study on Co(II) removal capacity from water samples by sorption using limestone and nanolimestone

Powdered nanolimestone (NLS) and limestone (LS) have been investigated as an adsorbent for the removal of cobalt from aqueous solutions. Batch experiments were carried out to investigate the effect of pH. The favorable pH for maximum cobalt adsorption was 6.8. The surface area increased in the case of NLS up to 6.2 m2/g, while it was equal to 0.5 m2/g in the case of LS. The adsorption capacity calculated by the Langmuir equation was 17.1 mg/g for LS and 60.0 mg/g for NLS at pH 6.8. The adsorption capacity increased with temperature and the kinetics followed a first-order rate equation. The enthalpy change (ΔHo) was 20.8 Jmol−1 for LS and 41.6 Jmol−1 for NLS, while entropy change (ΔSo) was 33.3 JK−1 mol−1 for LS and 74.8 JK−1 mol−1 for NLS, which substantiates the endothermic and spontaneous nature of the cobalt adsorption process. All of the results suggested that the NLS is very strong and could be an excellent nano-adsorbent for cobalt contaminated water treatment more than limestone.

Chemical pretreatments of Trapa bispinosa's peel (TBP) biosorbent to enhance adsorption capacity for Pb(ll)

In this study, Trapa bispinosa's peel (TBP) biomass is exploited as an effective, low cost and new adsorbent to remove Pb(II) from aqueous solution. TBP is pretreated and modified with HNO3, HClO4 and H2O2 to enhance the Pb(II) removal and it is perceived that chemical modifications enhance the adsorption capacity of TBP. The adsorption behavior of Pb(II) is studied under different conditions, including pH (3-6), TBP dose (0.050.8 g), stirring speed (100-200 rpm), initial Pb(II) ion concentration (25-400 mg L-1) and contact time (0-1440 min). Kinetic study reveals sorption is fast in first 15 to 30 min achieving equilibrium in 60 min with qmax (mg g-1) are 77.09, 105.40 and 123.82 for NT-TBP, NA-TBP and HCA-TBP respectively. The Langmuir model successfully defines the sorption data having higher R2 and good agreement between theoretical and experimental uptake capacity of Pb(II). The kinetic study exhibits that the pseudo-second order rate equation is better portrayed sorption process. TBP modified with HClO4 shows the highest metal uptake in comparison to HNO3, H2O2 modified TBP and native TBP.

Application of a Mixed Order Model to Determine the Rate Adsorption of 1-Nitronaphthalene onto Activated Carbon

This study investigated the adsorption kinetics of 1-nitronaphthalene solution (a polycyclic aromatic hydrocarbon, PAH) onto seven different masses of activated carbon. The coefficient of determination (r2) was used to determine the best-fit kinetic model and to confirm agreement between experimental data and the kinetic rate equations. The results indicated that adsorption could be defined with masses of 0.0200 g and 0.0501 g when fitted using a second order rate equation. Adsorption on to masses of 0.1003 g, 0.1203, 0.1501 g, and 0.2001 g was best defined when data were fitted to a pseudo second order rate equation. However, adsorption onto a mass of 0.0701g did not fit with any simple rate law. Consequently, a new mathematical mixed order equation was developed to determine the rates of adsorption and the rate constants by combining two orders of equations: the pseudo first order and pseudo second order, to achieve a better fit with the same data.