Titania nanowires as substrates for sensing and photocatalysis of common textile industry effluents

Sensing and photocatalysis of textile industry effluents such as dyes using mesoporous anatase titania nanowires are discussed here. Spectroscopic investigations show that the titania nanowires preferentially sense cationic (e.g. Methylene Blue, Rhodamine B) over anionic (e.g. Orange G, Remazol Brilliant Blue R) dyes. The adsorbed dye concentration on titania nanowires increased with increase in nanowire dimensions and dye solution pH. Electrochemical sensing directly corroborated spectroscopic findings. Electrochemical detection sensitivity for Methylene Blue increased by more than two times in magnitude with tripling of nanowire average length. Photodegradation of Methylene Blue using titania nanowires is also more efficient than the commercial P25-TiO₂ nanopowders. Keeping illumination protocol and observation times constant, the Methylene Blue concentration in solution decreased by only 50% in case of P25-TiO₂ nanoparticles compared to a 100% decrease for titania nanowires. Photodegradation was also found to be function of exposure times and dye solution pH. Excellent sensing ability and photocatalytic activity of the titania nanowires is attributed to increased effective reaction area of the controlled nanostructured morphology.     

Spectrophotometric determination of Blue Procion HEGN in effluents of textile industry exploiting the dye aggregation effect and flow injection analysis.

A new spectrophotometric method involving flow injection analysis and textile dye aggregation effect is proposed. The method is based on the aggregation effect of Blue Procion HEGN at pH 3, which relocates its maximum absorption wavelength from 620 to 776 nm, avoiding the interference of other blue textile dyes. For this task, a simple and robust flow injection system was designed, which became a very stable analytical method. When the system was applied to Blue Procion determination in effluent of textile industry, precise results were observed (RSD < 2% within 1.0 and 5.0 mg l(-1) HEGN). The analytical frequency was 80 measurements per hour; the analytical curve was linear from 1.0 to 5.0 mg l(-1) HEGN; the detection limit considering three times the standard deviation of the blank solution (n = 10) was estimated as 0.03 mg l(-1) HEGN; and recoveries between 95% and 105% were found. The system consumes 20 mg of sodium citrate and 125 microl of the sample per determination. No baseline drift was observed during extended (5 h) operation periods.     

Critical flux in NF of high molar mass polysaccharides and effluents from the paper industry

High molar mass polysaccharides (locust bean gum and karaya gum) and effluents from a mechanical pulp mill and a paper mill were nanofiltered with commercially available nanofiltration (NF) membranes. The effect of the filtration conditions on the flux (critical flux), retention, and the fouling of the membranes was studied. The experiments were conducted by increasing and decreasing the pressure and measuring the flux thus obtained.

The critical flux was observed to increase with increasing flow velocity and decreasing concentration. An increase in pH increased the electrostatic repulsion between the membrane and the dissociated (charged) components in the paper mill effluents. As a result, a higher critical flux was obtained and also the retentions of the charged substances improved. Only a weak form of the critical flux was observed with the mill effluents. The permeate flux deviated from the pure water flux even at the lowest pressure, but increased linearly with pressure until the weak form of the critical flux was exceeded. The small decrease in flux immediately after filtration was started was probably caused by the plugging of the free spaces in the membranes or by the adsorption of foulants onto the membrane surface.

In the filtrations with the high molar mass polysaccharides, a strong form of the critical flux as well as a weak form were observed. The significant irreversible fouling of the most hydrophobic membrane was due to adsorption of the model substances by hydrophobic interaction. A precleaning of the membranes with an alkaline cleaning agent improved the pure water fluxes by up to 30%, but it had only a small effect on the critical or the limiting flux. The pure water fluxes of precleaned membranes after filtration were still higher than the pure water fluxes of the untreated membranes before filtration.     

Removal of phenols from water and petroleum industry refinery effluents by activated carbon obtained from coconut coir pith

Coir pith obtained from the coir industry as waste biomass was used to prepare activated carbon by chemical activation using phosphoric acid (H₃PO₄). The influences of activation temperature and lasting time of activation on specific surface areas (SSA) of the activated carbons were observed. Physical characteristics of the activated carbon were investigated using X-ray diffraction (XRD), infra-red spectroscopy (IR), surface area analyzer, scanning electron microscopy (SEM), thermal analysis and potentiometric titration. The feasibility of using activated carbon for the removal of phenol (P), p-chlorophenol (PCP) and p-nitrophenol (PNP) from water and petroleum refinery industry effluents was investigated. The effects of contact time, adsorbent dose, ionic strength and initial concentration on the adsorption of phenols onto the activated carbon were investigated. The optimum pH for the maximum removal of phenols was 6.0. The equilibrium adsorption data of phenols were correlated to Langmuir and Freundlich isotherm models, the latter being the best fit of the experimental data. Dynamics of the sorption process and mass transfer were investigated using McKay and Urano-Tachikawa models. Adsorption kinetic data fits the Urano-Tachikawa kinetic model. The utility of the adsorbent was tested by using petroleum refinery industry effluent. The adsorbed phenols can be recovered by treatment with 0.1 M NaOH solution.     

Selective membrane alternative to the recovery of zinc from hot-dip galvanizing effluents

This work reports the study of the kinetics of zinc recovery from spent pickling solutions by means of emulsion pertraction technology (EPT) in order to reuse the metal in electrolytic processes. Tributyl phosphate (TBP) and service water were used as extraction (EX) and back-extraction (BEX) agents, respectively. Kinetic experiments were carried out in hollow fiber membrane contactors in order to analyse the influence of several operation variables on the rate of zinc recovery. A mathematical model that considers the mass transfer resistance shared between the organic liquid membrane and the organic phase boundary layer was developed; the mass transfer coefficients were estimated by means of the parameter estimation tool ASPEN CUSTOM MODELER (from ASPENTECH) to obtain the values k_m = 2.68 × 10⁻⁷ m/s and A_Vk_o = 0.0125 s⁻¹. Simulated results agreed satisfactorily well with experimental data. Consequently, the kinetic model and parameters were confirmed. Finally, a comparison between EPT and non-dispersive solvent extraction (NDSX) was carried out in order to evaluate the advantages and disadvantages of both membrane configurations.     

Carboxymethyl cellulose- and fluorapatite-coated silver[orthophosphate-bromide] nanostructures for photodegradation of an azo dye from the textile industry

Visible light photoactive silver[orthophosphate-bromide] loaded on fluorapatite (FA) and carboxymethyl cellulose (CMC) supports were prepared by an ionic liquid-assisted precipitation method and used as effective light driven heterogeneous systems for removal of Acid Blue 92 (AB92) azo dye and E. coli gram-negative bacteria from the wastewaters. The prepared samples were characterized by X-ray diffraction (XRD) powder, diffuse reflectance spectroscopy (DRS), Furrier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherms (BET). The XRD patterns well proved the formation of Ag₃PO₄ and AgBr photocatalytic crystalline phases of the nanostructures. Besides, the SEM images demonstrated that the photoactive particles were homogenously dispersed on the surface and the average size of the particles is below 90 nm. The antibacterial experiments showed that the products particularly the FA-based photocatalyst can also be utilized as efficient antimicrobial agents. According to the results, the CMC-based photocatalyst was more active during the first time of using while the other one was determined to be promising enough during the recycling tests.     

Evaluation of separation and purification processes in the antibiotic industry

Antibiotic production is a complex capital intensive process, which divides naturally into two segments, fermentation and separation/purification. The separation and purification section is very large as a result of the number of processing steps required (up to 60) and the need to purify and recycle large quantities of organic solvents. Separation and purification is not generic within the antibiotic industry. Not only does each individual antibiotic require a different separation process, but also there are many different separation schemes in use for the same antibiotic. Much research is currently in progress on three relatively new separation techniques on a commercial level, which may lead to substantial reductions in the complexity of the process; chromatography (both conventional preparative HPLC and annular chromatography), supercritical extraction, and various membrane processes.     

Inorganic speciation analysis of selenium by ion chromatography-inductively coupled plasma-mass spectrometry and its application to effluents from a petroleum refinery

A new method for the speciation analysis of selenite (Se-IV), selenate (Se-VI), and selenocyanate (SeCN⁻) is described and first results are presented on the distribution of these species in wastewater samples from a Brazilian oil refinery plant. The method is based on the ion chromatographic separation of these species followed by on-line detection of ⁷⁷Se, ⁷⁸Se, and ⁸²Se using quadrupole inductively coupled plasma-mass spectrometry (ICPMS). The system employed consisted of a HPLC pump equipped with a manual syringe loading injector, and an anion exchange column (Metrosep A Supp1), the latter interfaced with the ICPMS via a concentric nebulizer–cyclonic spray chamber sample introduction device. Several eluents already described in the literature for the speciation analysis of inorganic selenium were tested, permitting in most cases a good separation of Se(IV) and Se(VI), however, resulting all in very long residence times (> 30 min) and associated peak broadening for the SeCN⁻ ion. This drawback could be effectively avoided by using as the mobile phase a solution of cyanuric acid (3 mmol L⁻¹), modified with acetonitrile (2% v/v) and percchlorate acid (2.5 mmol L⁻¹). Typical retention times (s) for the three analyte species were: selenite (210) < selenate (250) < selenocyanate (450). Repeatabilities in peak position were better than 1% and in peak area evaluation about 3%. Absolute limits of detection (in ng) for these species using an ELAN 5000 instrument and a 500-μL sample injection loop are 0.04, 0.05 and 0.09, respectively. No certified reference materials were available for this study, however, results on spiked wastewater samples showed acceptable recoveries (80–110%) and repeatabilities (RSD < 5%), thus validating this method for its intended purpose. Once optimized, the method was applied to wastewater samples from an oil refinery plant. In all samples until now analyzed, selenocyanate was by far the most abundant selenium species reaching concentrations of up to 90 μg L⁻¹. Selenite was detected only in one sample and selenate could not identified in any of the samples analyzed. Total concentrations of selenium in most samples, assessed by hydride generation ICPMS and by solution nebulization inductively coupled plasma optical emission spectrometry (ICPOES), exceeded those obtained from speciation analysis, indicating the presence of other selenium species not observed by the here used methodology.     

Characterization of the different fractions obtained from the pyrolysis of rope industry waste

A study of the possibilities of pyrolysis for recovering wastes of the rope's industry has been carried out. The pyrolysis of this lignocellulosic residue started at 250 °C, with the main region of decomposition occurring at temperatures between 300 and 350 °C. As the reaction temperature increased, the yields of pyrolyzed gas and oil increased, yielding 22 wt.% of a carbonaceous residue, 50 wt.% tars and a gas fraction at 800 °C. The chemical composition and textural characterization of the chars obtained at various temperatures confirmed that even if most decomposition occurs at 400 °C, there are some pyrolytic reactions still going on above 550 °C. The different pyrolysis fractions were analyzed by GC–MS; the produced oil was rich in hydrocarbons and alcohols. On the other hand, the gas fraction is mainly composed of CO₂, CO and CH₄. Finally, the carbonaceous solid residue (char) displayed porous features, with a more developed porous structure as the pyrolysis temperature increased.     

Evaluation of toxic metals in the industrial effluents and their segregation through peanut husk fence for pollution abatement

The industrial pollution is exponentially growing in the developing countries due to the discharge of untreated effluents from the industries in the open atmosphere. This may cause severe health hazards in the general public. To reduce this effect, it is essential to remove the toxic and heavy metals from the effluents before their disposal into the biosphere. In this context, samples of the effluents were collected from the textile/yarn, ceramics and pulp/paper industries and the concentrations of the toxic metal ions were determined using neutron activation analysis (NAA) technique. The observed concentration values of the As, Cr and Fe ions, in the unprocessed industrial effluents, were 4.91 ± 0.8, 9.67 ± 0.7 and 9.71 ± 0.8 mg/L, respectively which was well above the standard recommended limits (i.e. 1.0, 1.0 and 2.0 mg/L, respectively). In order to remove the toxic metal ions from the effluents, the samples were treated with pea nut husk fence. After this treatment, 91.5% arsenic, 81.9% chromium and 66.5% iron metal ions were successfully removed from the effluents. Then the treated effluents contained concerned toxic metal ions concentrations within the permissible limits as recommended by the national environmental quality standards (NEQS).     

Recent developments and challenges of biocatalytic processes in the pharmaceutical industry

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Recent application of biochar on the catalytic biorefinery and environmental processes

Lignocellulosic biomass is an abundant and environment-friendly source for renewable energy production. The value and application of biochar, which is obtained from the thermochemical conversion of biomass, is increasing rapidly because of its high carbon content and porosity. The property of biochar, such as surface area, porosity, and number of functional groups, can be improved by controlling the conditions of biomass conversion, biochar activation, and functionalization methods. The production and activation of biochar as well as its potential use for soil remediation, pollutant adsorption, and biorefinery have been reviewed extensively over recent decades. This paper provides a conceptual approach for biochar production and activation together with its application as a catalyst for biorefineries and the removal of environmental contaminants.     

Recent application of biochar on the catalytic biorefinery and environmental processes

Biochar, produced and activated from thermochemical methods, was applied as catalyst for catalytic biorefinery and environmental pollutant removal. In this review, recent advanced studies of biochar catalyst were discussed.     

Determination of 19 volatile organic compounds in wastewater effluents from different treatments by purge and trap followed by gas-chromatography coupled to mass spectrometry

A rapid and simple methodology based on purge and trap with gas-chromatography coupled to triple quadrupole mass spectrometry has been developed for the analysis of 19 volatile organic compounds (VOCs) in wastewater (WW) effluents from four different treatments. The determination was carried out in the raw WW effluents, which were not submitted to any pre-treatment (e.g., filtration). A matrix effect study was also performed, concluding that solvent calibration was adequate to quantify VOCs in WW effluent samples containing a variety of suspended particulate matter. Adequate validation parameters were obtained with recovery values in the range 73–124% and precision values lower than 24%. Limits of quantification were established at 0.1 μg L^-1 for all VOCs. The proposed method was applied to the analysis of WW samples, detecting chloroform and toluene at concentrations ranging from 0.1 to 4.80 μg L^-1.     

Automated on-line preconcentration of palladium on different sorbents and its determination in environmental samples

The determination of noble metals in environmental samples is of increasing importance. Palladium is often employed as a catalyst in chemical industry and is also used with platinum and rhodium in motor car catalytic converters which might cause environmental pollution problems. Two different sorbents for palladium preconcentration in different samples were investigated: silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene tbiocarbohydrazide (DPTH-gel) and [1,5-Bis(2-pyridyl)-3-sulphophenyI methylene thiocarbonohydrazide (PSTH) immobilised on an anion-exchange resin (Dowex lx8-200)]. The sorbents were tested in a micro-column, placed in the auto-sampler arm, at the flow rate 2.8 mL min(-1). Elution was performed with 4 M HCl and 4 M HNO3, respectively. Satisfactory results were obtained for two sorbents.     

A whisker-like carbon composite for the immobilization of laccase and its bioelectrochemistry

A novel mesoporous carbon/whisker-like carbon (MCWC) composite was used for the immobilization of laccase (Lac) and its bioelectrochemical behaviors were studied. It was confirmed by XPS that Lac was strongly adsorbed on the surface of the MCWC composite. The cyclic voltammetric results showed that the immobilized Lac underwent a direct quasi-reversible electrochemical reaction. The value of the electron transfer rate constant k _s was estimated to be 0.770 s^?1, indicating a reasonably fast electron transfer between the immobilized Lac and the underlying electrode. The surface concentration (Γ) of Lac was estimated to be 2.730 × 10^?12 mol/cm². Further experimental results showed that the immobilized Lac displayed an appreciable electrocatalytic activity to the electrochemical reduction of O₂. These properties could be attributed to the particular structure of loosely packed nanometer-scale carbon whiskers and the existence of a large amount of oxygen-containing groups. The immobilization method and the novel carrier (MCWC) may find new applications in fabricating the biocatalysts for biofuel cells.     

Highly selective immobilization of Au nanoparticles onto isolated and dense nanopatterns of poly(2-vinyl pyridine) brushes down to single-particle resolution

Chemical patterns consisting of poly(2-vinyl pyridine) (P2VP) brushes in a background of a cross-linked polystyrene (PS) mat enabled the highly selective placement of citrate-stabilized Au nanoparticles (NPs) in arrays on surfaces. The cross-linked PS mat prevented the nonspecific binding of Au NPs, and the regions functionalized with P2VP brushes allowed the immobilization of the particles. Isolated chemical patterns of feature sizes from hundreds to tens of nanometers were prepared by standard lithographic techniques. The number of 13 nm Au NPs bound per feature increased linearly with increasing area of the patterns. This behavior is similar to previous reports using 40 nm particles or larger. Arrays of single NPs were obtained by reducing the dimensions of patterned P2VP brushes to below ~20 nm. To generate dense (center-to-center distance = 80 nm) linear chemical patterns for the placement of rows of single NPs, a block-copolymer (BCP)-assisted lithographic process was used. BCPs healed defects associated with the standard lithographic patterning of small dimensions at high densities and led to highly registered, linear, single NP arrays.     

Comprehensive evaluation of lipophilicity of biogenic amines and related compounds using different chemically bonded phases and various descriptors

The retention behavior for a series of biogenic amines and related sympathomimetic drugs has been investigated in reversed-phase thin-layer chromatography using RP-2, RP-8, RP-18W, and Diol stationary phase and mixtures of phosphate buffer (pH = 7.10) and methanol in different proportions as mobile phases. Several methodologies like arithmetic mean of experimental retention values, extrapolation to zero methanol concentration procedure and principal component analysis were applied to retention data values (R(M)) in order to determine relevant parameters (mean of R(M) - mR(M), R(M0), and scores corresponding to the first principal component - PC1/R(M) respectively) encoding information on the lipophilic behavior of compounds. High similarities in lipophilicity behavior of investigated amines were highlighted by mR(M) and PC1/R(M) lipophilicity indices for all of the studied stationary phases. The experimental results were compared with some computed lipophilicity parameters expressed as distribution coefficients at working pH (logD), partition coefficients (logP(N), logP(I), and diff(logP(N-I))) concerning both neutral and fully protonated species and difference between both species, and also with various lipophilicity values (logP) generated by different commonly used software. Significant correlations were observed between the experimental lipophilicity indices mR(M) respectively PC1/R(M) and diff(logP(N-I) ) values in all cases.     

Covalent immobilization of Candida antarctica lipase B on nanopolystyrene and its application to microwave-assisted esterification

Nanopolystyrene was used as a solid support for the covalent immobilization of Candida antarctica lipase B (CalB) using the photoreactive reagent 1-fluoro-2-nitro-4-azido benzene (FNAB) as a coupling reagent. The obtained derivative was then used as a biocatalyst in a microwave assisted esterification experiment. Factors such as contact time, pH, and enzyme concentration were investigated during immobilization. The hydrolytic activity, thermal, and operational stability of immobilized-CalB were determined. The maximum immobilized yield (218 μg/mg support) obtained at pH 6.8 exhibited optimum hydrolytic activity (4.42 × 10³ mU p-nitrophenol/min). The thermal stability of CalB improved significantly when it was immobilized at pH 10, however, the immobilized yield was very low (93.6 μg/mg support). The immobilized-CalB prepared at pH 6.8 and pH 10 retained 50% of its initial activity after incubation periods of 14 and 16 h, respectively, at 60 ℃. The operational stability was investigated for the microwave assisted esterification of oleic acid with methanol. Immobilized-CalB retained 50% of its initial activity after 15 batch cycles in the microwave-assisted esterification. The esterification time was notably reduced under microwave irradiation. The combined use of a biocatalyst and microwave heating is thus an alternative total green synthesis process.