Green Deep Eutectic Solvents (DESs) for Sustainable Metal Recovery from Thermally Treated PCBs: A Greener Alternative to Conventional Methods

Waste PCBs the core of e-waste is rich in copper, tin, zinc, iron, and nickel. Leaching base metals from PCB used to be done in toxic, corrosive acidic/alkali mediums. In this work, an environmentally friendly method for leaching metals from thermally treated PCBs (TPCBs) of mobile phones was proposed using choline chloride based deep eutectic solvents (DES). DES selectivity and solubility of metals from metal oxides were the main screening criteria. FA-ChCl had the maximum solubility of Cu, Fe, and Ni, while Urea-ChCl had high Zn selectivity and solubility. Oxalic acid has high selectivity for Sn. FA-ChCl extracted Cu and Fe best at 16 h, 100 °C, and 1/30 g/mL. Urea-ChCl extracted Zn (90.4±2.9 %) from TPCBs at 100 °C, 21 h, 1/20 g/mL, and 400 rpm. Oxalic acid (1 M) removed 92.3±2.1 % Sn from TPCBs in 1 h at 80 °C and 1/20 g/mL. The shrinking core model-based kinetic investigation of FA-ChCl for Cu extraction showed a diffusion-controlled process. The proposed method is greener than mineral acids utilized for metal extraction.

A feasible approach for the treatment of waste computer casing plastic using subcritical to supercritical acetone: Statistical modelling and optimization

Electronic waste (e-waste) usage has increased tremendously with the rapid evolution of technologies. The accumulated e-waste has now emerged as one of the crucial concerns regarding environmental pollution and human health. Recycling e-waste is commonly focused on metal recovery; nevertheless, a significant fraction of plastics (20-30%) are in e-waste. There is an indispensable need to focus on e-waste plastic recycling in an effective way, which has been mostly overlooked to date. An environmentally safe and efficient study is conducted using subcritical to supercritical acetone (SCA) to degrade the real waste computer casing plastics (WCCP) in the central composite design (CCD) of response surface methodology (RSM) to achieve the maximum oil yield of the product. The experiment parameters were varied in the temperature span of 150-300 °C, residence time between 30 and 120 min, solid/liquid ratio between 0.02 and 0.05 (g/ml), and NaOH amount from 0 to 0.5 g. Adding NaOH into the acetone helps to achieve efficient degradation and debromination efficiency. The study emphasized the attributes of oils and solid products recovered from the SCA-treated WCCP. The characterization of feed and formed products is performed with different characterization techniques such as TGA, CHNS, ICP-MS, FTIR, GC-MS, Bomb calorimeter, XRF, and FESEM. The highest oil yield achieved is 87.89% from the SCA process at 300 °C, in 120min, 0.05 S/L ratio, and 0.5 g of NaOH. GC-MS results disclose that the liquid product (oil) comprises single- and duplicate-ringed aromatic and oxygen-containing compounds. Isophorone is the significant component of the liquid product obtained. Furthermore, SCA's possible polymer degradation mechanistic route, bromine distribution, economic feasibility, and environmental aspect were also explored. This present work represents an environmentally friendly and promising approach for recycling the plastic fraction of e-waste and recovering valuable chemicals from WCCP.

A sustainable route for the recovery of metals from waste printed circuit boards using methanesulfonic acid

The rapid increase in electronic waste (e-waste) generation and its unsustainable management pose a threat to the environment and human well-being. However, various valuable metals are present in e-waste, which makes it a potential secondary source to recover metals. Therefore, in the present study, efforts were made to recover valuable metals (Cu, Zn, and Ni) from waste printed circuit boards (WPCB) of computers using methanesulfonic acid (MSA). MSA is contemplated as a biodegradable green solvent and has a high solubility for various metals. The effect of various process parameters (MSA concentration, H₂O₂ concentration, stirring speed, liquid to solid ratio, time, and temperature) was investigated on metal extraction to optimize the process. At the optimized process conditions, 100% extraction of Cu and Zn was achieved, while Ni extraction was around 90%. The kinetic study for metal extraction was performed using a shrinking core model and findings showed that MSA-aided metal extraction is a diffusion-controlled process. Activation energies were found to be 9.35, 10.89, and 18.86 kJ/mol for Cu, Zn, and Ni extraction, respectively. Furthermore, the individual recovery of Cu and Zn was achieved using the combination of cementation and electrowinning, which resulted in 99.9% purity of Cu and Zn. The current study proposes a sustainable solution for the selective recovery of Cu and Zn from WPCB.

A sustainable approach for material and metal recovery from E-waste using subcritical to supercritical methanol

The heterogeneous nature of e-waste, which is a rich source of metals, polymers, glass fibres and ceramics, is troublesome. Multi-step processes are employed to effectively treat e-waste with minimum environmental impact. In this research, a subcritical to supercritical methanol environment was investigated to pre-treat e-waste, recovering non-metallic fractions and eventually concentrate metals from e-waste. Experiments were conducted in the temperature range of 150 °C to 300 °C at an autogenous pressure with initial atmospheric pressure. The mechanism of depolymerization was investigated by varying reaction time from 30 min to 240 min; solid to liquid ratio of 1:10 to 1:30 g/ml in a batch reactor under N₂ environment. Comparative analysis of liquid products obtained after Supercritical Methanol (SCM) treatment for both Waste Random Access Memory (WRAM) and Waste Printed Circuit Board (WPCB) was done with pyrolyzed oil/liquid product. This research briefly illustrates oil and solid product compositional changes with operating temperature, pressure, and solid/liquid ratio range. The metal concentrations of copper, nickel, silver, zinc, and gold are greater than 90% after SCM treatment. For comparison, the feed material was pyrolyzed under the same condition, the difference in oil and solid products are assessed. In the end section, the environmental and economic benefits of SCM were also discussed compared to other supercritical and conventional technologies. An efficient and greener approach of supercritical solvent is proposed via this research for e-waste recycling.

Microwave-assisted extraction of lignin from coconut coir using deep eutectic solvents and its valorization to aromatics

Lignin is a rich renewable source of aromatics present in lignocellulosic biomass (LCB). The extraction of lignin from the intricate LCB network is a challenging task for successful commercialization of sustainable biorefineries. In the present study, a series of choline chloride (ChCl)-carboxylic acid based deep eutectic solvents (DESs) were used for the extraction of lignin from coconut coir under microwave irradiation. Among the synthesized DESs, ChCl: lactic acid (LA) (1:4) gave the highest lignin yield of 82% with >95% purity. Interestingly, the severity factor (H factor) for the pretreatment process was found to be a significantly lower (55.5) as compared to reported studies due to efficient microwave heating. Moreover, the DES showed good recyclability for four recycle runs thus making it a promising candidate for the delignification of LCB. Finally, the extracted lignin was converted to aromatics via catalytic transfer hydrogenation (CTH) using Ru/C and isopropanol as in-situ hydrogen donor.

Valorisation of xylose to renewable fuels and chemicals, an essential step in augmenting the commercial viability of lignocellulosic biorefineries

Biologists and engineers are making tremendous efforts in contributing to a sustainable and green society. To that end, there is growing interest in waste management and valorisation. Lignocellulosic biomass (LCB) is the most abundant material on the earth and an inevitable waste predominantly originating from agricultural residues, forest biomass and municipal solid waste streams. LCB serves as the renewable feedstock for clean and sustainable processes and products with low carbon emission. Cellulose and hemicellulose constitute the polymeric structure of LCB, which on depolymerisation liberates oligomeric or monomeric glucose and xylose, respectively. The preferential utilization of glucose and/or absence of the xylose metabolic pathway in microbial systems cause xylose valorization to be alienated and abandoned, a major bottleneck in the commercial viability of LCB-based biorefineries. Xylose is the second most abundant sugar in LCB, but a non-conventional industrial substrate unlike glucose. The current review seeks to summarize the recent developments in the biological conversion of xylose into a myriad of sustainable products and associated challenges. The review discusses the microbiology, genetics, and biochemistry of xylose metabolism with hurdles requiring debottlenecking for efficient xylose assimilation. It further describes the product formation by microbial cell factories which can assimilate xylose naturally and rewiring of metabolic networks to ameliorate xylose-based bioproduction in native as well as non-native strains. The review also includes a case study that provides an argument on a suitable pathway for optimal cell growth and succinic acid (SA) production from xylose through elementary flux mode analysis. Finally, a product portfolio from xylose bioconversion has been evaluated along with significant developments made through enzyme, metabolic and process engineering approaches, to maximize the product titers and yield, eventually empowering LCB-based biorefineries. Towards the end, the review is wrapped up with current challenges, concluding remarks, and prospects with an argument for intense future research into xylose-based biorefineries.

Controlling liquid hydrocarbon composition in valorization of plastic waste via tuning zeolite framework and SiO2/Al2O3 ratio

Abundance of plastic waste has become threat to the mankind and aquatic life and thus needs to be recycled or converted into value added products. Liquefaction of waste plastics via catalytic cracking is one the efficient routes towards plastic waste management. Concerning this, in present study, conversion of polymer mixture containing polypropylene, low-density polyethylene and high-density polyethylene (PP, LDPE and HDPE) was done for the production of gasoline and diesel range hydrocarbons using two-step cracking approach. MWW and MFI (12 and 10 member ring structures respectively) type zeolites having different pore structure and acidity were used for catalytic cracking of polymer feed at 350 °C. Investigations revealed that MWW type zeolite having two independent pore channels selectively provides gasoline range of hydrocarbons (C₇-C₁₂, 99.12%) in polymer cracking reaction as compared to MFI type which results in C₁₃-C₂₀ range of hydrocarbons (73.19%). Hydrocarbon compositions were confirmed from GC-MS, ¹H, ¹³C NMR and FT-IR techniques. In activity results it was observed that acidity of zeolites affects the liquid yield and hydrocarbon distribution as analysed by using zeolites of two different SiO₂/Al₂O₃ (SAR) ratio (30 and 55) which directs that zeolite (MFI/MWW) with lower SAR (30) having higher acidity results in higher yield of fuel range liquid hydrocarbons as compared to higher SAR (55) zeolite. Characterization studies such as XRD, N₂-physisorption, NH₃-TPD, FE-SEM and EDX were performed to check the physiochemical properties of zeolite and correlated with the activity. Overall, the present investigation provides detailed comparative study on plastic degradation using MFI and MWW type zeolites resulting into different range of liquid hydrocarbons.

Efficient recovery of Cu and Ni from WPCB via alkali leaching approach

The large generation of electronic waste (e-waste) is posing a serious threat to society. It is important to develop sustainable technology for the effective management of e-waste and the recovery of valuable metals from it. The present study employed hydrometallurgical approach for Cu and Ni extraction from waste printed circuit boards (WPCB) of mobile phones. This study demonstrates the application of ammonia-ammonium sulfate leaching for the maximum recovery of Cu and Ni. Investigations revealed that the most favourable reaction parameters for efficient metal extraction are - ammonia concentration - 90 g/L, ammonium sulfate concentration - 180 g/L, H₂O₂ concentration - 0.4 M, time - 4 h, liquid to solid ratio - 20 mL/g, temperature - 80 °C and agitation speed - 700 rpm. Under these conditions, 100% Cu and 90% Ni were extracted. Furthermore, the kinetic study was performed using the shrinking core model which revealed that the internal diffusion is the rate-controlling step for Cu and Ni extraction. The activation energies for Cu and Ni extraction were found out to be 4.5 and 5.7 kJ/mol, respectively. Finally, Cu was recovered with 98.38% purity using electrowinning at a constant DC voltage of 2.0 V at Al cathode. The present study provides a solution for concurrent extraction of Cu and Ni from the raw WPCB of mobile phones and selective recovery of Cu from metal leached solution. The process has the potential to recover the resources from WPCB while minimising the pollution caused by mismanagement of WPCB.

High quality liquid fuel production from waste plastics via two-step cracking route in a bottom-up approach using bi-functional Fe/HZSM-5 catalyst

Plastic waste is a serious menace to the world due to its fastest growth rate of ~ 5% per annum and requires efficient technologies for its safe disposal. Plastic liquefaction producing liquid hydrocarbons is an effective way to dispose waste plastics in an eco-friendly manner. In present study, high quality liquid fuel is produced from waste plastics via two-step bottom-up cracking approach. A comparative analysis of liquid products obtained in thermal and catalytic cracking performed at relatively lower temperature (350 °C) with minimal catalyst to plastic feed ratio (1:30) has been studied. Catalytic cracking via two-step bottom-up route provides higher fraction of fuel range hydrocarbons in comparison to the thermal cracking. Catalytic cracking is performed using two different catalysts; HZSM-5 and 5%Fe/HZSM-5 in which later results in higher liquid yield (76 wt%) than former (60 wt%) having comparable fuel characteristics. GC-MS results confirm that liquid product obtained via catalytic cracking contains higher fraction of fuel range hydrocarbons (C₆-C₂₀); 66.39% for 5%Fe/HZSM-5 and 47.33% for HZSM-5 which is comparatively higher than that obtained in thermal cracking (27.39%). FT-IR, ¹H and ¹³C NMR spectroscopic studies confirm that liquid hydrocarbons obtained via catalytic cracking have comparable chemical characteristics with fuel range hydrocarbons. Physiochemical properties of catalysts are studied using XRD, XPS, BET, FE-SEM, HR-TEM, NH₃-TPD and H₂-TPR techniques and correlated with activity results. Analysis of commercial diesel fuel is also incorporated to compare the fuel characteristics of liquid products.

Pretreatment of lignocellulosic biomass: A review on recent advances

Depleting fossil reserves and growing energy needs have raised the demand for an alternative and clean energy source. The use of ubiquitously available lignocellulosic biomass for developing economic and eco-friendly large scale biorefinery applications has provided the much-needed impetus in this regard. The pretreatment process is a vital step for biomass transformation into added value products such as sugars, biofuels, etc. Different pretreatment approaches are employed to overcome the recalcitrance of lignocellulosic biomass and expedite its disintegration into individual components- cellulose, hemicellulose, and lignin. The conventional pretreatment methods lack sustainability and practicability for industrial scale up. The review encompasses the recent advances in selective physical and chemical pretreatment approaches such as milling, extrusion, microwave, ammonia fibre explosion, eutectic solvents etc. The study will allow a deeper understanding of these pretreatment processes and increase their scope as sustainable technologies for developing modern biorefineries.

Unravelling the reactivity of metastable molybdenum carbide nanoclusters in the C-H bond activation of methane, ethane and ethylene

C-H bond activation steps in non-oxidative methane dehydroaromatization (MDA), constitute a key functionalization of the reactant and adsorbed species to form aromatics. Previous studies have focused on studying the energetics of these steps at the most stable active sites involving molybdenum carbide species. Herein, a different paradigm is presented via studying the reactivity of a metastable molybdenum carbide (Mo₂C₆) nanocluster for the C-H bond activation of methane, ethane, and ethylene and comparing it with the reactivity of the lowest energy Mo₂C₆ nanocluster. Interestingly, the metastable nanocluster is observed to result in a consistent reduction (by half) in the C-H bond activation barrier of the respective alkane and alkene molecules compared to the global minimum isomer. This specific metastable form of the nanocluster is identified from a cascade genetic algorithm search, which facilitated a rigorous scan of the potential energy surface. We attribute this significant lowering of the C-H bond activation barrier to unique co-planar orbital overlap between the reactant molecule and active centers on the metastable nanocluster. Based on geometrical and orbital analysis of the transition states arising during the C-H bond activation of methane, ethane, and ethylene, a proton-coupled electron transfer mechanism is proposed that facilitated C-H bond cleavage. Motivated by the high reactivity for C-H bond activation observed on the metastable species, a contrasting framework to analyze the elementary-step rate contributions is presented. This is based on the statistical ensemble analysis of nanocluster isomers, where the calculated rates on respective isomers are normalized with respect to the Boltzmann probability distribution. From this framework, the metastable isomer is observed to provide significant contributions to the ensemble average representations of the rate constants calculated for C-H bond activation during the MDA reaction.

Environmentally friendly approach for the recovery of metallic fraction from waste printed circuit boards using pyrolysis and ultrasonication

Electronic waste (e-waste) with an annual growth rate of 3-5% is one of the fastest-growing waste streams. The unregulated accumulation and improper recycling can cause grave hazards to human beings and the environment. On the contrary, e-waste can be considered as a secondary source of metals and energy due to its high metal content and polymeric material. Thus, the present study demonstrates technology for the metallic fraction recovery and the production of valuable gases from e-waste. The process involves pyrolysis at a temperature range of 200 °C-600 °C in a fixed bed setup for 10-60 min. Under optimized operating conditions, 35 wt% combustible gases and 60 wt% solid product were obtained at a pyrolysis temperature of 400 °C in 20 min. The gaseous product consisted of CH₄, H₂, CO and CO₂, having the heating value 28 MJ/kg whereas, the solid product is a mixture of metals and other solid residue material. Treatment of the solid product using an ultrasonication process resulted in around 90 wt% recovery of metallic fraction, thereby leaving behind solid residue. Moreover, the transfer of precious metals (Au, Ag, Pd and Pt) was nearly 100% to the metallic fraction. This process combines mild temperature pyrolysis and ultrasonication process to provide a solution for efficient management of e-waste, metallic fraction recovery and valuable gases production.

An ultra-light flexible aerogel-based on methane derived CNTs as a reinforcing agent in silica-CMC matrix for efficient oil adsorption

Bamboo shaped multi-walled Carbon Nanotubes were synthesized by the thermo-catalytic decomposition of methane in a modified chemical vapour deposition reactor. The prepared carbon nanotubes were reinforced in the mero-hydrophobic carboxymethyl cellulose and silica matrix for the preparation of low density, highly flexible aerogel. The synthesized aerogel exhibited a large specific surface area and uniform pore structure as confirmed by the nitrogen adsorption-desorption analysis. The water contact angle of 148.8° for the aerogel demonstrated that the synthesized aerogels were superhydrophobic in nature. The performance of aerogels was tested for the adsorption of singer oil and motor oil. Investigations revealed that aerogel can adsorb more than 28 times its weight effectively. Moreover, the adsorbed oil can be recovered by mechanical squeezing owing to its flexible nature. In addition, the aerogel could maintain its oil adsorption capacity even after 5 regeneration cycles, demonstrating superior recyclability. The peculiar properties - outstanding flexibility and superhydrophobicity exhibited by the aerogels establish them as a proficient and recyclable oil adsorbents during the oil seepage.

Greener approach for the extraction of copper metal from electronic waste

Technology innovations resulted into a major move from agricultural to industrial economy in last few decades. Consequently, generation of waste electronic and electrical equipments (WEEE) has been increased at a significant rate. WEEE contain large amount of precious and heavy metals and therefore, can be considered a potential secondary resource to overcome the scarcity of metals. Also, presence of these metals may affect the ecosystem due to lack of adequate management of WEEE. Building upon our previous experimental investigations for metal extraction from spent catalyst, present study explores the concept of green technology for WEEE management. Efforts have been made to recover base metal from a printed circuit board using eco-friendly chelation technology and results were compared with the conventional acid leaching method. 83.8% recovery of copper metal was achieved using chelation technology whereas only 27% could be recovered using acid leaching method in absence of any oxidant at optimum reaction conditions. Various characterization studies (energy dispersive X-ray analysis, scanning electron microscopy, X-ray diffraction, inductive coupled plasma spectrophotometry) of Printed Circuit Board (PCB) and residues were performed for qualitative and quantitative analysis of samples. Significant metal extraction, more than 96% recovery of chelating agent, recycling of reactant in next chelation cycle and nearly zero discharge to the environment are the major advantages of the proposed green process which articulate the transcendency of chelation technology over other conventional approaches. Kinetic investigation suggests diffusion controlled process as the rate determining step for the chelate assisted recovery of copper from WEEE with activation energy of 22kJ/mol.

Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient

Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday's law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.

Chelation technology: a promising green approach for resource management and waste minimization

Green chemical engineering recognises the concept of developing innovative environmentally benign technologies to protect human health and ecosystems. In order to explore this concept for minimizing industrial waste and for reducing the environmental impact of hazardous chemicals, new greener approaches need to be adopted for the extraction of heavy metals from industrial waste. In this review, a range of conventional processes and new green approaches employed for metal extraction are discussed in brief. Chelation technology, a modern research trend, has shown its potential to develop sustainable technology for metal extraction from various metal-contaminated sites. However, the interaction mechanism of ligands with metals and the ecotoxicological risk associated with the increased bioavailability of heavy metals due to the formation of metal-chelant complexes is still not sufficiently explicated in the literature. Therefore, a need was felt to provide a comprehensive state-of-the-art review of all aspects associated with chelation technology to promote this process as a green chemical engineering approach. This article elucidates the mechanism and thermodynamics associated with metal-ligand complexation in order to have a better understanding of the metal extraction process. The effects of various process parameters on the formation and stability of complexes have been elaborately discussed with respect to optimizing the chelation efficiency. The non-biodegradable attribute of ligands is another important aspect which is currently of concern. Therefore, biotechnological approaches and computational tools have been assessed in this review to illustrate the possibility of ligand degradation, which will help the readers to look for new environmentally safe mobilizing agents. In addition, emerging trends and opportunities in the field of chelation technology have been summarized and the diverse applicability of chelation technology in metal extraction from contaminated sites has also been reviewed.

Study of beam loading and its compensation in the Compact Ultrafast Terahertz Free-Electron Laser injector linac

The RF properties of an accelerating structure, and the pulse structure and charge per bunch in the electron beam propagating through it are important parameters that determine the impact of beam loading in the structure. The injector linac of the Compact Ultrafast Terahertz Free-Electron Laser (CUTE-FEL) has been operated with two different pulse structures during initial commissioning experiments and the effect of beam loading on the accelerated electron beam parameters has been studied analytically for these two pulse structures. This paper discusses the analytical study of beam loading in a Standing Wave, Plane Wave Transformer linac employed in the CUTE-FEL setup, and a possible technique for its compensation for the electron beam parameters of the CUTE-FEL. A parametric study has been performed to study beam loading for different beam currents and to optimize injection time of the electron beam to compensate beam loading. Results from the parametric study have also been used to explain previously observed results from acceleration experiments in the CUTE-FEL setup.

A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (e(b)) ~1, resonant frequency f(π) = 2856 MHz, and waveguide-to-cavity coupling coefficient β(π) ~1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (f(f) and f(h)), and of the waveguide-to-full-cell coupling coefficient (β(f)). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL∕SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

Oxygen glucose deprivation model of cerebral stroke in PC-12 cells: glucose as a limiting factor

Optimum time points for oxygen-glucose deprivation (OGD) and re-oxygenation have been identified to suggest the suitability of PC-12 cells as rapid and sensitive in vitro model of cerebral stroke. Further, the precise role of glucose as one of the limiting factors was ascertained. PC-12 cells were subjected to receive OGD of 1-8 h followed by re-oxygenation for 6 to 96 h in medium having glucose 0-10 mg/ml. Loss of cell viability was assessed using trypan blue dye exclusion and MTT assays. The significant (p < 0.05) reduction in percent viable cell count was started at 2 h of OGD (80.7 +/- 2.0) and continued in further OGD periods (3, 4, 5, 6, 7, and 8 h), i.e. 65.7 +/- 3.5, 59.7 +/- 4.6, 54.3 +/- 3.2, 44.7 +/- 2.9, 20.3 +/- 4.3, 5.7 +/- 2.0 of counted cells, respectively. Cells growing in glucose-free medium have shown a gradual (p < 0.001) decrease in cell viability throughout the re-oxygenation. Re-oxygenation of 24 h was found to be first statistically significant time point for all the glucose concentrations. Glucose concentration during re-oxygenation was found to be one of the key factors involved in the growth and proliferation in PC-12 cells. The OGD of 6 h followed by a re-oxygenation period of 24 h with 4-6 mg/ml glucose concentration could be recorded as optimum conditions under our experimental conditions.

Extraction of nickel from spent catalyst using fresh and recovered EDTA

This study investigates the possibility of recovering nickel from spent catalyst (NiO/Al(2)O(3)) used in the fertilizer industry. EDTA (ethylenediaminetetraaceticacid) di sodium salt was used as a chelating to extract the Ni after which sulfuric acid was added to obtain NiSO(4). The dechelation process takes 5-6h to break the complex and EDTA which was recovered as H(4)EDTA acid in the solid form and solution contains NiSO(4). The objective was to evaluate the nickel removal efficiency of EDTA and reusability of recovered EDTA. The parameters affecting nickel recovery were EDTA concentration, time of chelation, catalyst to liquid ratio (s:l), mixing speed, pH and catalyst particle size. The extraction was up to 95% under the following conditions: 0.8M concentration of EDTA, solid to liquid ratio 1:50 (g/ml), particle size 100 microm, pH 10, 10h of chelation time, 700 rpm and 100 degrees C. Up to 95% of the EDTA could be recovered without losing significant activity.

Melatonin protects against experimental reflux esophagitis

Reflux esophagitis (RE), a major gastrointestinal disorder results from excess exposure of the esophageal mucosa to acidic gastric juice or bile-containing duodenal contents refluxed via an incompetent lower esophageal sphincter. Recent studies implicated oxygen derived free radicals in RE induced esophageal mucosal damage resulting in mucosal inflammation. Thus, control over free radical generation and modulation of inflammatory responses might offer better therapeutic effects to counteract the severity of RE. In this context we investigated the effect of melatonin against experimental RE in rats. Melatonin pretreatment significantly reduced the haemorrhagic lesions and decreased esophageal lipid peroxidation aggravated by RE. Moreover, the depleted levels of superoxide dismutase and glutathione observed in RE were replenished by melatonin signifying its free radical scavenging properties and antioxidant effects resulting in the improvement of esophageal defense mechanism. Further melatonin repressed the upregulated levels of expression of proinflammatory cytokines like, TNF-alpha, IL-1beta and IL-6 in RE. However, increased levels of the anti-inflammatory cytokine IL-10 remained unaltered after melatonin administration signifying its immunomodulatory effect through suppression of Th1-mediated immune responses. The involvement of receptor dependent actions of melatonin against RE were also investigated with MT2 receptor antagonist, luzindole (LUZ). LUZ failed to antagonize melatonin's protective effects against RE indicating that melatonin mediated these beneficial effects in a receptor-independent fashion. Thus, esophageal mucosal protection elicited by melatonin against experimental RE is not only dependent on its free radical scavenging activity but also mediated in part through its effect on the associated inflammatory events in a receptor-independent manner.

PARFLEX--a very useful drug for management of surgical pain

The aim was to assess and document the efficacy and tolerability of parflex (FDC of aceclofenac with paracetamol and serratiopeptidase) in management of pain and inflammation in adult patients undergoing surgical procedures (or operations). The design was open, prospective, non-comparative and multi-dose study of patients undergoing surgical procedures at a leading, tertiary-care, teaching hospital (setting) in Lucknow, the name being, King George's Medical College, Lucknow 226003. The patients were 50 adult patients of either sex undergoing surgery. They were given 1 tablet twice daily, taken after meals. Treatment duration was for a total of up to 7 days (intervention). Primary efficacy variables were relief from postoperative pain. Secondary efficacy variables were global assessment of efficacy and toleration by patients and treating physicians. Record was made of spontaneously reported adverse events with their nature, intensity and outcome (tolerability). Out of 50 patients, 31% were (ENT), 36% were (Orthopaedic) and 33% were (Gynaecology). They were enroled in this study. The observations made were mean pain score showed significant improvement with study drug - decreasing from 2.66 at baseline to 1.36 after 48 hours, and to 0.8 at the end of study. Composite score for pain, fever and swelling also showed substantial gains visit-on- visit-decreasing from 3.62 at baseline to 2.04 after 48 hours, and to 0.98 at final visit. None of the patients reported any adverse event. Global efficacy assessment was rated as 'excellent or good' by 54% of patients and in 59% of patients by their treating physicians. To conclude, parflex is an effective analgesic, anti-inflammatory drug that has a valuable therapeutic option for controlling pain and inflammation after surgical procedures.

Thermodynamic and breakthrough column studies for the selective sorption of chromium from industrial effluent on activated eucalyptus bark

Studies were carried out on adsorption of Cr(VI) on an adsorbent made from eucalyptus bark. Results revealed that sorption of chromium on activated eucalyptus bark (AEB) was endothermic in nature. Thermodynamic parameters such as the entropy change, enthalpy change and Gibb's free energy change were found out to be 100.97 J mol(-1)K(-1), 33 kJ mol(-1) and -0.737 kJ mol(-1), respectively. Industrial chrome effluent of different chromium concentration at different pH was used as feedstock for the fixed bed adsorption studies. When effluent was fed to the column at low pH of 2, the breakthrough volume increased significantly compared to effluent at higher pH of 4.85. The surface properties of sorbent were characterized by the Scanning electron microscopy, X-ray diffraction technique and Infrared techniques. It was concluded that AEB sorbent column could be used effectively for removal of chromium from industrial effluents by reducing the pH of chrome effluent to two and at optimal column conditions.

Solidification/stabilization of arsenic containing solid wastes using portland cement, fly ash and polymeric materials

Stabilization/solidification (S/S) is used as a pre-landfill waste treatment technology that aims to make hazardous industrial wastes safe for disposal. Cement-based solidification/stabilization technology is widely used because it offer assurance of chemical stabilization of many contaminants and produce a stable form of waste. The leaching behavior of arsenic from a solidified/stabilized waste was studied to obtain information about their potential environmental risk. Activated alumina (AA) contaminated with arsenic was used as a waste, which was stabilized/solidified (S/S) using ordinary portland cement (C), fly ash (FA), calcium hydroxide (CH) and various polymeric materials such as polystyrene and polymethyl methacrylate (PMMA). Toxicity characteristics leaching procedure (TCLP) and semi-dynamic leach tests were conducted to evaluate the leaching behavior of arsenic. Formations of calcite along with precipitate formation of calcium arsenite were found to be responsible for low leaching of arsenic from the stabilized/solidified samples. Effective diffusivity of arsenic ion from the matrix and leachablity index was also estimated. Minimum leaching of the contaminant was observed in matrix having AA+C+FA+CH due to the formation of calcite.

Removal of chromium from industrial waste by using eucalyptus bark

Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879 kJ mol(-1) for Cr(VI) and -3.885 kJ mol(-1) for Cr(III) for removal from industrial effluent. The negative value of deltaG0 indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH 2. Adsorption capacity was found to be 45 mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250 mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.

A field study and continuous removal of fluoride in a packed column

The synthetic water performance in the light of fluoride removal was studied and compared with the actual fluoride contaminated water of different selected water collection stations. An indegeneous activated alumina was used as adsorbent. The performance of the column for fluoride contaminated water was about 94% fluoride reduction at a pH value of 7.0 and the presence of total dissolved solids (T.D.S.). 2114 mg/L in subsoil water decreased the fluoride removal by 5%.

Equilibrium and kinetics studies on removal of arsenite by iron oxide coated activated alumina

Arsenic in drinking water is causing much concern because of its toxicity. It occurs in water naturally as As(III) and As(V). Of these As (III) is more toxic. Adsorption on activated alumina has been one of the most commonly used methods for As (V) removal from drinking water. But it is not very effective for As (III). Activated alumina was modified by coating it with Iron oxide to make it suitable for As (III) adsorption. Iron oxide coated activated alumina was tested for its effectiveness as an adsorbent for As (III). The As (III) adsorption was strongly dependent on pH and a maximum removal of 98% was observed at a pH of 12. The adsorption process followed a first order kinetics. The equilibrium was attained after 8 hours. The kinetic study was carried out with different initial As (III) concentration. It was observed that time taken to attain equilibrium was independent of initial concentration but percentage removal decreased with increasing initial concentration. The adsorption isotherms were fitted well to both Langmuir and Freundlich equation.

Modification of reserpine-induced emetic response in pigeons by alpha 2-adrenoceptors

In the present study, an attempt has been made to elucidate the role of alpha 2-adrenoceptors in reserpine-induced emesis in pigeons. Reserpine was found to induce dose-dependent emesis and a 500 micrograms kg-1 dose was found to be the 100% emetic dose. alpha 2-adrenoceptor agonists clonidine and alpha-methylnoradrenaline inhibited the reserpine induced emesis. Out of the two selective alpha 2-adrenoceptor antagonists idazoxan and yohimbine, only the latter induced a dose-dependent emesis. However, both the drugs potentiated reserpine-induced emesis and antagonised its inhibition by clonidine. Prior depletion of monoamines by reserpine also blocked the emetic response of reserpine. These observations indicate that release of monoamines is responsible for its emetic response in pigeons which is modulated by presynaptic alpha 2-adrenoceptors in a predictable manner.

Dopaminergic involvement in the effects of piracetam on foot shock induced aggression in mice

The effects of piracetam-a nootropic drug, were studied on foot shock induced aggressive behaviour in mice. Intraperitoneal injection of piracetam resulted in a biphasic response i.e.; initial excitation followed by inhibition of the aggressive behaviour. The initial excitation was observed with only 100 and 50 mg/kg doses of piracetam and not with the lower doses (25 and 12.5 mg/kg). Dopaminergic receptor blocker haloperidol (0.5; 0.25 and 0.12 mg/kg, ip) and pimozide (1.0 mg/kg, ip) produced inhibition of the aggressive behaviour. Lowering of the dose of haloperidol to 0.06 mg/kg resulted in an excitation of the aggressive behaviour. No motor deficit or catalepsy was observed with either haloperidol or pimozide injected in the doses indicated above. Pretreatment of the mice with haloperidol (0.12; 0.25 and 0.5 mg/kg) led to a dose-dependent blockade of the piracetam (100 mg) induced excitation of the aggressive behaviour, but the inhibition of the aggressive behaviour was not blocked by pretreatment with the excitatory dose of haloperidol. Similarly, pimozide (1.0 mg/kg) pretreatment also effectively blocked the excitatory effect of piracetam on aggressive behaviour. The results suggest the involvement of dopaminergic system in the excitatory effects of piracetam on aggressive behaviour. The inhibitory effect of piracetam appears to be independent of this mechanism.

Serotonergic modulation of spinal cord sympathetic preganglionic neurone activity in cardiovascular regulation

The present study demonstrates the effect of activation of spinal serotonergic receptors on heart rate, blood pressure and cardiac arrhythmia induced by coronary artery ligation in cervical spinal cord transected and bilaterally vagotomized dogs. Intrathecal injection of serotonin (5-HT) evoked a fall in blood pressure (mean decrease, 16 +/- 3) and a decrease in heart rate (mean change, 24 +/- 6) and these effects were blocked by intrathecal pretreatment with methysergide. The magnitude of ventricular ectopics evoked by coronary artery ligation was decreased by serotonin (mean decrease, 31 +/- 5%), and this effect of serotonin was blocked by methysergide pretreatment intrathecally (mean change, 7 +/- 5%). Methysergide per se, increased the magnitude of ventricular ectopics (mean increase, 24 +/- 5%). The serotonergic receptors of the spinal cord appear to have an inhibitory influence on the cardiovascular functions.

Central alpha-adrenoceptor influence over the cardiovascular reflexes activated by veratrine

Intravenous veratrine induced alterations in cardiovascular parameters in cats were used as a tool for assessing the influence of central alpha-adrenoceptors over reflex adjustments in the heart rate and blood pressure. Blockade of central alpha 2-adrenoceptors with idazoxan or yohimbine, inhibited, while their activation by clonidine, as also blockade of alpha 1-adrenoceptors, with prazosin, potentiated the veratrine induced bradycardia. The hypotensive effect was relatively unaltered by these treatments. Low doses of clonidine potentiated the veratrine-induced bradycardia. It appears that alpha 2-adrenoceptor mechanisms exert greater control over the reflex regulation of heart rate than over reflex control of blood pressure.

Atrial natriuretic factor suppresses M-current in frog but not in rat sympathetic neurones

The effects of atrial natriuretic factor (ANF) were investigated on rat and bullfrog sympathetic ganglia. Although there was little effect on neurones from rat superior cervical ganglion (SCG), B-cells in bullfrog paravertebral ganglia (BFSG) were depolarized. This depolarization was often associated with an increase in excitability and suppression of a voltage-dependent K+ current, the M-current (IM). ANF did not affect the amplitude of the nicotinic EPSP in either ganglion.

Angiotensin receptors at the spinal cardiovascular loci

Intrathecal injection of graded doses of angiotensin elicited a significant, dose-related rise in blood pressure without affecting heart rate. Tachyphylaxis appeared with repeated intrathecal injections but intravenous angiotensin could elicit pressor effects at this stage. Intrathecal administration of saralasin per se, did not affect resting heart rate or blood pressure. However, pretreatment with saralasin completely antagonized the intrathecal angiotensin-induced rise in blood pressure without significantly altering the effect of intravenous angiotensin. A facilitatory role for blood pressure regulation is suggested for the angiotensin receptors at the spinal cardiovascular loci.

Role of medullary cholinoceptors in baroreflex bradycardia

Cholinergic receptors present in three medullary nuclei namely, the nucleus tractus solitarii (NTS), nucleus ambiguous (AMB) and the dorsal motor nucleus of the vagus nerve (DMV) have been studied with regard to their role in regulation of heart rate (HR), blood pressure (BP) and baroreceptor reflex activation induced bradycardia in cats. Microinjection of carbachol into NTS was without effect while administration of carbachol or pilocarpine into AMB and DMV elicited dose related decrease in HR without affecting BP. These effects were completely antagonized by ethylbenztropine. Bilateral muscarinic cholinoceptor blockade of either AMB or DMV, with ethylbenztropine, produced a partial inhibition of the baroreflex bradycardia while intracisternal ethylbenztropine completely abolished this reflex response. Involvement of muscarinic cholinoceptors of AMB or DMV in baroreflex mediated adjustments of HR is therefore suggested.

Nucleus locus coeruleus: evidence for alpha 1-adrenoceptor mediated hypotension in the cat

Microinjection of noradrenaline or phenylephrine into the nucleus locus coeruleus of cats induced a dose dependent and long lasting hypotension. Clonidine was required in a dose of 1 microgram for eliciting a significant hypotension while its lower doses (up to 500 ng) failed to elicit any significant cardiovascular alteration. The effects on heart rate evoked by these agents were insignificant. Microinjection of alpha-adrenoceptor antagonists prazosin, piperoxan and RX 781094 per se did not evoke any significant cardiovascular effects and only prazosin pretreatment showed dose dependent antagonism of the hypotensive effect of clonidine. Piperoxan was required in four times higher dose (20 micrograms) to partially antagonize the clonidine induced hypotension. RX 781094, a selective alpha 2-adrenoceptor antagonist, however, even up to a dose of 20 micrograms (four times that of prazosin) did not alter the effect of clonidine. Similar pattern of antagonism was also seen for noradrenaline and phenylephrine. The results demonstrate the presence of alpha 1-adrenoceptors in the nucleus locus coeruleus, the activation of which leads to a fall in blood pressure.

An investigation into the mechanism of cardiovascular responses elicited by electrical stimulation of locus coeruleus and subcoeruleus in the cat

Electrical stimulation of locus coeruleus (LC) and subcoeruleus (SC) elicited an increase in heart rate (HR) and blood pressure (BP). Adrenergic neurone blockade in the posterior hypothalamus with guanethidine and also bilateral adrenalectomy completely blocked the LC stimulation induced cardiovascular responses. The cardiovascular responses elicited by electrical stimulation of SC were, however, unaffected by the former and only partially inhibited by the latter. It is suggested that the LC stimulation-evoked rise in HR and BP is mediated by catecholamine release from the adrenal medulla due to an activation of the hypothalamic-adrenal axis. The cardiovascular responses elicited by stimulation of SC are mainly due to activation of the sympathetic preganglionic neurones and are further augmented by the adrenal catecholamine release.

Spinal site of antiarrhythmic action of morphine and pethidine in normal and spinal cord transected dogs

In coronary artery ligated conscious dogs, intravenous (i.v.) injection of both morphine (8.0 mg/kg) and pethidine (12.0 and 24.0 mg/kg) inhibited the cardiac arrhythmia while naloxone (1.0 mg/kg) facilitated it. Intravenous pretreatment with naloxone completely blocked the morphine induced inhibition of the arrhythmia. Pethidine, however, elicited significant inhibition of the arrhythmia in the naloxone pretreated animals but its duration of action was markedly reduced. The temporal effect of i.v. injection of xylocaine (24.0 mg/kg) was parallel to that of pethidine (24.0 mg/kg) injected i.v. in the naloxone pretreated animals. In cervical spinal cord transected and bilaterally vagotomized dogs, i.v. injection of only 50.0 micrograms/kg of morphine elicited significant inhibition of the arrhythmia which was completely blocked by intrathecal pretreatment with a small dose (1.0 micrograms/kg) of naloxone. The same dose of naloxone, when given intravenously, failed to block the effect of morphine. The antiarrhythmic activity of morphine against the cardiac arrhythmia induced by coronary artery ligation appears to be due to activation of spinal opioid receptors. The local anaesthetic activity of pethidine contributes towards its early phase of antiarrhythmic activity.

Adrenergic influences on the spinal cardiovascular neurones

In cervical spinal cord transected and bilaterally vagotomized dogs, intrathecal (i.t.) injection of clonidine decreased the resting heart rate and mean arterial pressure (MAP) while isoprenaline increased the heart rate. The clonidine induced bradycardia and hypotension were antagonized by piperoxan pretreatment. Similarly, the isoprenaline induced tachycardia was antagonized by pretreatment (i.t.) with atenolol. Intrathecal atenolol per se decreased the heart rate and MAP while piperoxan had no effect. The post-coronary artery ligation cardiac arrhythmia, in the cervical spinal cord transected and bilaterally vagotomized dogs, was inhibited by clonidine, phenylephrine and methoxamine and facilitated by isoprenaline. beta-Adrenoreceptor antagonists propranolol, atenolol and acebutolol, given intrathecally, inhibited while piperoxan facilitated the cardiac arrhythmia. The clonidine and isoprenaline induced changes in the arrhythmia were antagonized by i.t. pretreatment with piperoxan and atenolol respectively. It appears that the alpha-adrenoreceptors are inhibitory while beta-adrenoreceptors are facilitatory for spinal control of heart rate and blood pressure and for post-coronary artery ligation cardiac arrhythmia.

Cardiovascular responses elicited by microinjection of cholinergic agents into nucleus dorsalis raphe in cats

The effect of cholinomimetics and cholinoceptor blocking agents microinjected into nucleus dorsalis raphe (NDR) has been studied on heart rate and blood pressure to identify the nature and role of these cholinoceptors in cardiovascular regulation. Microinjection of the cholinoceptor agonists, pilocarpine and carbachol into NDR elicited bradycardia and hypotension accompanied by salivation which could be blocked by local pretreatment with ethybenztropine (a muscarinic receptor blocker), but not by chlorisondamine (a nicotinic receptor blocker). Pretreatment with atropine methylnitrate (i.v.), which blocks only peripheral muscarinic receptors, did not prevent these cardiovascular responses evoked by carbachol microinjection. These cholinergic receptors seem to be localized in NDR since, microinjection of carbachol into neural structures adjoining NDR, failed to induce any cardiovascular responses. Muscarinic cholinoceptors are present in NDR which modulate cardiovascular activity by influencing sympathetic preganglionic neurons in the intermediolateral columns of the spinal cord.

Effects of morphine and pethidine on coronary vascular resistance, blood pressure, and myocardial infarction-induced cardiac arrhythmias

In the present study, the effects of morphine and pethidine on coronary vessel resistance (CPP), blood pressure (BP), and experimental myocardial infarction-induced cardiac arrhythmia were investigated. Both morphine and pethidine induced a fall in CPP and BP and inhibited the cardiac arrhythmia. The morphine effects on CPP and BP were largely blocked by mepyramine. The effects of pethidine, on the other hand, were not blocked by mepyramine, propranolol, or atropine. An interesting dose dependent inhibition of cardiac arrhythmia was observed with pethidine.

Cholinergic influences on the spinal cardiovascular neurones

1 In bilaterally vagotomized and spinal cord (C1) transected dogs, intrathecal (i.t.) injection of pilocarpine decreased while DMPP increased the blood pressure. These responses were antagonized by i.t. pretreatment with ethylbenztropine and chlorisondamine respectively. 2 No change in the resting heart rate occurred after intrathecal injection of cholinergic drugs in these animals. 3 The post-coronary artery ligation cardiac arrhythmia, in bilaterally vagotomized and spinal (C1) transected dogs, was inhibited by i.t. pilocarpine and chlorisondamine and facilitated by ethylbenztropine and DMPP. 4 The effects of muscarinic and nicotinic receptor agonists on the arrhythmia were blocked by their respective blockers. 5 It appears that the muscarinic receptors are inhibitory while nicotinic receptors are facilitatory for spinal control of vasomotor tone and the post-coronary artery ligation cardiac arrhythmia. However, the spinal muscarinic and nicotinic receptors do not appear to have a significant role in the regulation of normal heart rate.

Synthesis and pharmacological studies of 2'-sulphonyl[3-(3H-2,4-disubstituted-1,5-benzodiazepino)]-2,5-dimethyl-6,7-benzomorphans

2'-Sulphonyl[3-(3H-2,4-dimethyl-1,5-benzodiazepino)]-2,5-dimethyl-6,7-ben zomorphan (3a), 2'-sulfonyl[3-(3H-2 methyl-4-phenyl-1,5-benzodiazepino)]-2,5-dimethyl-6,7-benzomorphan (3b) and 2'-sulfonyl [3-(3H-2-methyl-4-oxo-5H-1.5-benzodiazepino)]-2,5-dimethyl-6,7-benzomorphan (3c), synthesized from 2,5-dimethyl-6,7-benzomorphan (1) in three steps via chlorosulphonation, condensation with sodium salt of acetylacetone, benzoylacetone and ethyl acetoacetate separately and condensation with o-phenylenediamine, were studied for their pharmacological activities. It was found that 3a has mild CNS depressant, analgesic and anticonvulsant (against petit mal type of seizures) activities. 3b has significant anti-depressant and mild analgesic activities while 3c has CNS depressant, mild analgesic and anticonvulsant activities (against petitmal type seizures).