Hazardous Organic Wastes Research Articles

Research on the microscale effects of fuel pellets carrying chemical pesticide distillation residues

To effectively deal with organic hazardous wastes generated in the production processes of chemical pesticide industries. In this study, the strong shear force generated by high-speed rotating blades was utilized to fully mix and stir pasty or viscous liquid organic hazardous wastes with porous solid fuels. The wastes were broken down into small molecular clusters and evenly distributed on the surfaces of the pores of porous solid fuel particles. This study then investigated the thermal characteristics of fuel particles carrying the distillation residues of chemical pesticides under microscale effects, the volatilization and destruction removal characteristics, the formation of pollutants, and the migration and transformation of F and Cl elements. The results showed that when the average diameter of the fuel particles was 6 mm and the mass ratio of the chemical pesticide distillation residue to the fuel particles was 2:3, small molecular clusters of the residue were evenly distributed on the surfaces of the fuel particles, with a dispersity of 67 %. The volatilization rate of the irritating odors in the coated particles was less than 2 %. With an increase in the proportion of the chemical pesticide distillation residue, the ignition temperature of the particles decreased, the thermal stability increased, the burnout temperature rose, and the maximum weight loss rate first increased and then decreased. The Ca and alkali metal oxides in the fuel particles had a significant effect on fixing chlorine and fluorine.

NH4Cl recovery from high-ammonia organic waste liquor by electrolysis with aluminum soluble anode

High-ammonia organic waste liquor is regarded as highly toxic and non-biodegradable due to containing high concentration of ammonia and organic refractory compounds. Treating high-ammonia organic waste liquor could be costly in the need of large energy or chemical agent input. Recovery of ammonium is an alternative way because high ammonium waste liquor could act as a reservoir of nitrogenous fertilizer. In this study, NH4Cl was separated from waste liquor by electrolysis with aluminum-soluble anode. The white foamy substances with NH4Cl purity over 90 % were produced at a current density of 12.5 mA/cm2 with 100 min electrocution. The white foamy substance production rate was increased as pH rose, and NH4Cl purity increased from 82.44 % at pH 4 to 91.34 % at pH 6. The soluble aluminum from anode sacrifice promoted crystallization and separation of NH4Cl by participating in the formation of CGAs (Colloidal Gas Aphrons) and improving their stability. Organic substances in the liquor functioned as surfactant to generate of CGAs, CGAs carried NH4Cl crystals floated to the surface and formed the white foamy substance. The study proposes an efficient, sustainable method for the hazardous high-ammonia organic waste liquor resource utilization.

Eco-Friendly Stability Indicating HPLC Method for Estimation of Elbasvir and Grazoprevir by Quality by Design Approach

Introduction: The pharmaceutical industry faces a significant problem as a result of the worldwide requirement to modify processes in order to comply with the green analytical chemistry (GAC) requirements. An enormous amount of organic hazardous waste is produced by high-performance liquid chromatography (HPLC), one of the methods employed the most frequently at different stages in the pharmaceutical sector. Aim: To develop analytical quality by design-aided stability indicating green high-performance liquid chromatography (HPLC) method for estimation of Elbasvir and Grazoprevir in a dosage form. Material and Methods: The critical chromatographic factors were the % of ethanol in the mobile phase, flow rate, and their overall effect on the responses like asymmetry, theoretical plates, and resolution were studied to optimize the method. Green analytical chemistry (GAC) has mainly focused on developing analytical methods that are safe for the environment. Therefore, it is imperative that the GAC principles be applied in pharmacological analysis. A rotatable central composite design was employed, and the optimized conditions for chromatographic separation were made with a run time of 5 minutes using Zorbax C18 column (4.6× 150 mm, 5 µm) with 0.1% Trifluoroacetic acid and ethanol (40:60 v/v) as components of a mobile phase, flowing at a rate of 1.0 ml/minute. Photodiode array detection was carried out at 253 nm. Results: The retention time was 1.8 min for EBS and 2.84 min for GZP. According to the ICH guidelines, the proposed method was validated and stress studies revealed that Elbasvir and Grazoprevir are prone to acidic, basic, and oxidation stress conditions. An analytical eco-scale score evaluated the greenness profile and a software-based evaluation. Conclusion: The developed HPLC method is eco-friendly and shall be adopted in the routine quality control of Elbasvir and Grazoprevir in a tablet dosage form.

Microstructural evaluation of composites incorporated with industrial waste

Oil sludge is waste, which has a potential impact on nature and human health. Solidification/stabilization technology has stood out as an effective approach to treating this waste by transforming it into non-toxic, insoluble forms. Thus, the objective of the present research was to treat hazardous organic waste, through stabilization by solidification and evaluate the resulting matrix, through X-ray Diffraction Analysis, Scanning Electron Microscopy and Thermogravimetric Analysis. Cementitious matrices were prepared with addition of 5% and 20% oil sludge. After the curing time, the specimens were ground and submitted for characterization analyses. This, indicated a high organic mass to be treated and presented an amount of chromium above the maximum permissible limit. The incorporation of the oil sludge did not have a significant impact on the hydration reactions of the cementitious matrices, as indicated by the characteristic peaks of Portlandite and Calcium Silicate. The scanning electron microscopy analysis pointed out that the oil sludge did not interfere in the cement hydration reactions, resulting in the formation of the main hydration products. There was a significant difference in mass losses between the treatment with 5% and 20% oil sludge, with greater losses when incorporating a larger amount of residue, while the curing time had no significant influence.

Assessment of enzymatically synthesized DNA for gene assembly.

Phosphoramidite chemical DNA synthesis technology is utilized for creating de novo ssDNA building blocks and is widely used by commercial vendors. Recent advances in enzymatic DNA synthesis (EDS), including engineered enzymes and reversibly terminated nucleotides, bring EDS technology into competition with traditional chemical methods. In this short study, we evaluate oligos produced using a benchtop EDS instrument alongside chemically produced commercial oligonucleotides to assemble a synthetic gene encoding green fluorescent protein (GFP). While enzymatic synthesis produced lower concentrations of individual oligonucleotides, these were available in half the time of commercially produced oligonucleotides and were sufficient to assemble functional GFP sequences without producing hazardous organic chemical waste.

MICROBIAL BIOREMOVAL OF DIVALENT TOXIC METALS

The problems of polymetallic wastewater treatment from mining enterprises as well as the accumulation of organic waste are acute worldwide. The application of any existing methods of wastewater purification is ineffective and impossible due to the huge volumes and high concentrations of metals. Similarly, modern methods are ineffective for the treatment of huge amounts of organic waste. Therefore, there is a necessity to develop novel environmental biotechnologies providing the simultaneous degradation of organic waste and detoxification of toxic metals. The purpose of the work was to theoretically substantiate and experimentally confirm the possibility of toxic divalent cations removal using dissimilatory sulfate reduction via anaerobic fermentation of ecologically hazardous model organic waste. Colorimetric and potentiometric methods were used for pH and redox potential measurement; volumetric and chromatographic methods – to control volume and composition of synthesized gas; permanganate method – to determine the concentration of dissolved organic carbon (DOC); photocolorimetric method via the qualitative reaction with Nessler’s reagent was used to determine the concentration of ammonium ions. The Co2+ and Ni2+ content in medium was determined by a colorimetric method with 4-(2-pyridylazo)resorcinol (PAR). Fermentation parameters were calculated with the use of mathematical and statistical ones. Modified Postgate B medium with different sources of carbon and energy (potatoes, alanine, and meat) was used for cultivation of dissimilatory sulfate reducing bacteria. The anaerobic microbiome obtained from the sludge of methane tanks showed high efficiency to remove Co2+ and Ni2+ from the liquid medium. The highest efficiency (100% in 9 days) was observed when alanine was used as a source of carbon and energy. The slowest metal precipitation process occurred using meat (20 days). Also, the use of a protein substrate did not provide the expected alkalinization of the medium, which could significantly accelerate the process of metal precipitation. The precipitation of cobalt and nickel cations during the hydrogen fermentation of potato starch was complicated by acidification of the medium, but it was equally effective when the pH was adjusted. The proposed approach, the slow dissimilatory sulfate reduction, due to the sparingly soluble calcium sulfate as electron acceptor, can be used as a basis for the development of new biotechnologies for the treatment of wastewater contaminated with divalent heavy metals with the simultaneous treatment of ecologically hazardous compounds.

Numerical simulation study on the formation and control of HCl during the gasification of industrial organic hazardous waste

The utilization of industrial organic waste instead of coal by high temperature gasification to produce syngas is a promising way to reduce carbon emissions. The distinct property of industrial hazardous waste is characterized as high content of chlorine and volatile organics, which is significantly different from coal-water slurry. Herein, novel numerical models were established to simulate to the formation and control of HCl in the Texaco gasifier, where the chlorine-containing substances were simplified as dichloromethane to describe the mass transfer during the gasification. The models presented a good accuracy with the minimum error of 0.55% in syngas components prediction. The simulation demonstrated that HCl was generated near the nozzle, and the increasing of CaO amount and the decreasing of its particle size had positive effect on dechlorination. However, excessively reducing the size of CaO below 0.1 mm decreased its promoting effect, and high temperature in flame zone inhibited the dechlorination reaction. Therefore, the models developed in this work provided the feasibility of the general numerical simulation method to optimize the operating conditions in order to reduce the corrosion of chlorine to equipment and improve the stability of operation during the gasification process of organic hazardous waste.

The co-pyrolysis of waste urea-formaldehyde resin with pine sawdust: co-pyrolysis behavior, pyrocarbon and its adsorption performance for Cr (VI).

Urea-formaldehyde (UF) resin is difficult to degrade and classified as hazardous organic waste. To address this concern, the co-pyrolysis behavior of UF resin with pine sawdust (PS) was studied, and the adsorption properties of pyrocarbon were evaluated with Cr (VI). Thermogravimetric analysis revealed that adding a small amount of PS can improve the pyrolysis behavior of UF resin. Based on the Flynn Wall Ozawa (FWO) method, the kinetics and activation energy values were estimated. It was observed that when the amount of UF resin exceeded twice that of PS, the activation energy of the reaction decreased, and they acted synergistically. The characterization of pyrocarbon samples showed that the specific surface area increased with the increase of temperature, while the content of functional groups showed the opposite trend. Intermittent adsorption experiments showed that 5UF + PS400 achieved 95% removal of 50mg/L Cr (VI) at 0.6g/L dosage and at pH 2. The adsorption process was consistent with the Langmuir isotherm and pseudo-second-order kinetics, and the maximum adsorption was 143.66mg/g at 30 ℃. Furthermore, the adsorption process consisted of electrostatic adsorption, chelation, and redox reaction. Overall, this study provides a useful reference for the co-pyrolysis of UF resin and the adsorption capacity of pyrocarbon.

Utilization of chemically modified coal fly ash as cost-effective adsorbent for removal of hazardous organic wastes

Disposal of dyes wastewater into aquatic streams is considered as a major challenge due to its effect on water ecosystem. Direct dyes have a complex aromatic structure. Therefore, it is difficult to separate them from industrial wastewater. Conversely, fly ash is a main by-product pollutant generated from coal burning to fulfill energy requirements. In this study, thermochemical treatment process was applied to coal fly ash (CFA) in order to increase its surface area, improve its pore’s structure and enhancing its adsorption capacity for direct blue 78 dye (DB78) removal. The treated coal fly ash (TCFA) was characterized by physicochemical analyses such as XRD, XRF, TGA, SEM, FTIR, surface area (SBET) and particles size analysis. Batch experiments were conducted to analyze the adsorption behavior for TCFA and to examine the DB78 dye removal efficiency. The physicochemical analysis results indicated that a higher increase in CFA surface area from 9.6 to 60.4 m2g−1 was obtained due to the modification process. The maximum removal efficiency using TCFA was 99.7% for initial dye concentration 10 mg/L and TCFA dose 2 g/L. The adsorption isotherm was studied by Langmuir and Freundlich model using different dye concentrations. The results showed that equilibrium data followed closely Langmuir isotherm model (R2 = 0.99) indicating monolayer and homogeneous adsorption process.

Catalytic pyrolysis of oily sludge with iron-containing waste for production of high-quality oil and H2-rich gas

Oily sludge (OS), as a kind of organic hazardous waste with complex components, is suitable for treatment by pyrolysis. To attain effective removal of petroleum hydrocarbons and explore synergistic disposal for multi-source solid wastes, the catalytic effects of steel slag (SS) and red mud (RM) were investigated in this work. They could reduce the activation energy, accelerate OS degradation and shift the degradation of petroleum hydrocarbons towards lower temperature. What’s more, RM with higher iron content worked better, gained more pyrolytic gas and higher H2 production as well. More pyrolytic gas production was obtained when RM addition was at a low proportion. However, excessive catalyst would play a certain inhibitory role. The addition of RM promoted oil recovery at low temperature (400–500 °C) but brought more gas originating from oil cracking at high temperature (600 °C). At 400 °C, the oil yield elevated continuously with prolonging retention time. Nevertheless, even if the retention time was long enough, the harmless disposal for OS could not be completed with the catalysis of RM. Finally, the pristine minerals in RM were co-pyrolysis with OS individually to explore catalytic contributions. Metal oxides could enhance the gas yield and reduce the oil yield. The order of catalytic capacities was Fe2O3＞CaO＞SiO2＞Al2O3. Fe2O3 promoted H2 production and conversion from heavy oil into light fuels. Besides, Fe2O3 was reduced into Fe3O4 with part of [O] shifting into oil. CaO, SiO2, and Al2O3 could reduce the oxygen content in the pyrolytic oil through their acid-base properties to improve the oil quality. This work summarized the functions of various components in RM, might provide inspiration for getting insight into the application of collaborative treatment of different solid wastes.

Facile Synthesis of MgO Nanoparticle-Embedded Fe/N/S Codoped Carbon Materials from Oily Sludge for Efficient CO2 Capture

Oily sludge generated from the modern petrochemical industry is a large-scale hazardous solid waste. Pyrolysis with efficient catalysts is considered as a promising technology to convert the oily sludge into value-added chemicals or fuels without significant impact on the environment, but the solid char with spent catalysts does not find an application. In this study, the solid char obtained from catalytic pyrolysis of the oily sludge is applied as an adsorbent for CO2 capture. The char can be regarded as MgO nanoparticle-embedded Fe/N/S codoped carbon (MgO·FeOx@NSC) based on its structure and composition. MgO·FeOx@NSC presents a favorable performance toward CO2 capture. The maximum CO2 adsorption capacity is 4.57 mol/kg, and this value remains unchanged for more than 10 cycles of reuse. The mechanism for CO2 capture is analyzed with Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Physical adsorption and chemical interaction are identified as the primary contributors to the CO2 adsorption with MgO·FeOx@NSC, in which MgO, nitride-N, and sulfide-S are the main species contributing to the chemical interactions between CO2 and MgO·FeOx@NSC. This study will open up a new way for the sustainable management of hazardous organic solid wastes.

Valorization of Hazardous Organic Solid Wastes towards Fuels and Chemicals via Fast (Catalytic) Pyrolysis

The management of municipal and industrial organic solid wastes has become one of the most critical environmental problems in modern societies. Nowadays, commonly used management techniques are incineration, composting, and landfilling, with the former one being the most common for hazardous organic wastes. An alternative eco-friendly method that offers a sustainable and economically viable solution for hazardous wastes management is fast pyrolysis, being one of the most important thermochemical processes in the petrochemical and biomass valorization industry. The objective of this work was to study the application of fast pyrolysis for the valorization of three types of wastes, i.e., petroleum-based sludges and sediments, residual paints left on used/scrap metal packaging, and creosote-treated wood waste, towards high-added-value fuels, chemicals, and (bio)char. Fast pyrolysis experiments were performed on a lab-scale fixed-bed reactor for the determination of product yields, i.e., pyrolysis (bio)oil, gases, and solids (char). In addition, the composition of (bio)oil was also determined by Py/GC-MS tests. The thermal pyrolysis oil from the petroleum sludge was only 15.8 wt.% due to the remarkably high content of ash (74 wt.%) of this type of waste, in contrast to the treated wood and the residual paints (also containing 30 wt.% inorganics), which provided 46.9 wt.% and 35 wt.% pyrolysis oil, respectively. The gaseous products ranged from ~7.9 wt.% (sludge) to 14.7 (wood) and 19.2 wt.% (paints), while the respective solids (ash, char, reaction coke) values were 75.1, 35, and 36.9 wt.%. The thermal (non-catalytic) pyrolysis of residual paint contained relatively high concentrations of short acrylic aliphatic ester (i.e., n-butyl methacrylate), being valuable monomers in the polymer industry. The use of an acidic zeolitic catalyst (ZSM-5) for the in situ upgrading of the pyrolysis vapors induced changes on the product yields (decreased oil due to cracking reactions and increased gases and char/coke), but mostly on the pyrolysis oil composition. The main effect of the ZSM-5 zeolite catalyst was that, for all three organic wastes, the catalytic pyrolysis oils were enriched in the value-added mono-aromatics (BTX), especially in the case of the treated wood waste and residual paints. The non-condensable gases were mostly consisting of CO, CO2, and different amounts of C1–C4 hydrocarbons, depending on initial feed and use or not of the catalyst that increased the production of ethylene and propylene.

Audit And Analysis Of Waste Management In Baucau Municipality, Timor-Leste

Baucau is a municipality of Timor Leste, on the north coast in the eastern part of the country. The capital city is also named Baucau. The population in this municipality is 123,203 people (2015 census) and the area is 1,494 km². With a large population, which results in the production of waste increasing every day but the people in the municipality of Baucau face a lack of landfills and poor waste management. Many people in the municipality litter in drainage canals and public places whose sources come from household, commercial and office activities, so the researcher aims to 1.) examine the quantity and characteristics of waste from household activities and commercial activities in Bahu village (urban). , Tirilolo (peri-urban) and Caibada (rural) and 2.) studied the existing condition of waste management in the municipality of Baucau. From the results of the study, it was stated that in the three villages the composition of waste produced was organic waste, Metals, E-waste, Paper, cardboard, carton, Plastic bottles/PET, hazardous waste and glass. From household activities that produce waste, the highest is Bahu village (urban) with a total weight of 189,664 Kg, followed by Tirilolo (peri-urban) village with a total weight of around 155,224 Kg and the lowest is Caibada village (rural) reaching 106.655 Kg. From commercial activities consisting of 2 (two) hotels, 2 (two) supermarkets and 1 (one) restaurant. The three commercial activities that produce the most waste is supermarkets with a total waste weight of 86,323 Kg, followed by restaurants with a total weight of 57,886 Kg, and the lowest is hotels with a total weight of 6,799 Kg. The management of household, commercial and office waste in Baucau Municipality currently consists of three (3) parts: 1) Waste is transported by SMASA, 2) Discarded carelessly, and 3) Burned.

Emission Characteristics of NOx and SO2 during the Combustion of Antibiotic Mycelial Residue.

The antibiotic mycelial residue (AMR) generated from cephalosporin C production is a hazardous organic waste, which is usually disposed of by landfilling that causes potential secondary environmental pollution. AMR combustion can be an effective method to treat AMR. In order to develop clean combustion technologies for safe disposal and energy recovery from various AMRs, the emission characteristics of NOx and SO2 from AMR combustion were studied experimentally in this work. It was found that the fuel-N is constituted by 85% protein nitrogen and 15% inorganic nitrogen, and the fuel-S by 78% inorganic sulfur and 22% organic sulfur. Nitrogen oxide emissions mainly occur at the volatile combustion stage when the temperature rises to 400 °C, while the primary sulfur oxide emission appears at the char combustion stage above 400 °C. Increasing the combustion temperature and airflow cause higher NOx emissions. High moisture content in AMR can significantly reduce the NOx emission by lowering the combustion temperature and generating more reducing gases such as CO. For the SO2 emission, the combustion temperature (700 to 900 °C), airflow and AMR water content do not seem to exhibit obvious effects. The presence of CaO significantly inhibits SO2 emission, especially for the SO2 produced during the AMR char combustion because of the good control effect on the direct emission of inorganic SO2. Employing air/fuel staging technologies in combination with in-situ desulfurization by calcium oxide/salts added in the combustor with operation temperatures lower than 900 °C should be a potential technology for the clean disposal of AMRs.

Stationary Phases for Green Liquid Chromatography.

Industrial research, including pharmaceutical research, is increasingly using liquid chromatography techniques. This involves the production of large quantities of hazardous and toxic organic waste. Therefore, it is essential at this point to focus interest on solutions proposed by so-called “green chemistry”. One such solution is the search for new methods or the use of new materials that will reduce waste. One of the most promising ideas is to perform chromatographic separation using pure water, without organic solvents, as a mobile phase. Such an approach requires novel stationary phases or specific chromatographic conditions, such as an elevated separation temperature. The following review paper aims to gather information on stationary phases used for separation under purely aqueous conditions at various temperatures.

Catalytic pyrolysis of oil-based drill cuttings over metal oxides: The product properties and environmental risk assessment of heavy metals in char

Oil-based drill cuttings (OBDC), a hazardous organic waste generated from the exploration and extraction of shale gas fields, have received widespread attention for their safe disposal and utilization. In this study, OBDC pyrolysis experiments were conducted on a fixed-bed reactor. The effects of temperature (450 °C, 500 °C, 550 °C, and 600 °C) and catalysts (MgO, Fe2O3, and CaO) on product distribution, oil quality, and potential ecological risk assessment of heavy metals were investigated. Results revealed that the oil yield reached the maximum (14.94%) at 500 °C in uncatalyzed cases. The addition of catalysts could increase the total yield of oil and gas. In particular, the oil yield increased by 13.32% with CaO catalysis, while the oil recovered by MgO and Fe2O3 was almost the same as without catalyst. In addition, the higher low heating value (LHV) of oil (41.46 MJ/kg) and gas (34.07 MJ/Nm3) were found with CaO catalysis, implying that CaO has better performance on recovery of oil and gas than MgO and Fe2O3. Moreover, the oil content of char was far below 0.3%, the potential ecological risk assessment of heavy metal in char showed slight risks to the environment, suggesting that char can be treated as general solid waste.

Treatment of Organic Wastewater by Supercritical Water Oxidation

Supercritical water oxidation (SCWO) is a robust process in removing the hazardous organic wastes. Therefore, it is necessary to improve the SCWO process to eliminate the organic hazardous wastes. In present work, SCWO process used cyclohexylamine (CHA) as the organic chemical model. The co-oxidizers consisted of propylene glycol (PG), methanol and the oxygen source was hydrogen peroxide. The experiments were conducted using at a laboratory scale. A plug-flow reactor was utilized at different operating temperatures ranging from 425 to 525 ºC, the critical pressure was 25 MPa. At working temperatures, the co-oxidizer and the oxidant ratios were also investigated . The results indicated that the temperature had an impact on the removal efficiency of cyclohexylamine. The maximum total organic carbon removal (TOC) in the presence of propylene glycol was achieved with 98% at 525 ºC and the residence time was 14 s.

Degradation of urea-formaldehyde resin residues by a hydrothermal oxidation method into recyclable small molecular organics

Urea-formaldehyde (UF) resin residues and the related product wastes as organic hazardous wastes are difficult to be biodegraded or recycled. In this research, a hydrothermal oxidation method using hydrogen peroxide (H2O2) solution has been developed for the degradation and recycling of UF resin residues. The effects of solution concentration, temperature, and time on the degradation efficiency and products of UF resin residues were studied. Under optimal conditions, i.e., 140 °C and 5 wt% H2O2 solution, over 75% of UF resin residues was degraded after 3 h. The degradation efficiency is much higher than that of the traditional hydrothermal treatment or acid hydrolysis method. In addition, results from Fourier transform infrared spectroscopy (FTIR), gas chromatography–mass spectroscopy (GC–MS), nuclear magnetic resonance spectroscopy (NMR), and X-ray diffraction (XRD) confirmed that H2O2 solution degrades UF resin residues to low molecular compounds, such as alcohols, methylal, and amides. This research provides a novel and high-efficient hydrothermal oxidization process for the degradation of UF resin residues, which might be a promising environmentally friendly and low-cost method for the disposal and recycling of industrial UF resin residues.

Solid-State Thermolysis of 1D and 3D Cd-Coordination Polymers of l-methionine Derived Ligand to CdS Nanospheres: Facile Synthesis, Charecterization and Dye degredation Studies

• This article represents synthesis of coordination polymers 1/2 possessing one-dimensional (1D) and three-dimensional (3D) framework respectively. • The coordination polymers were characterized by various spectroscopic and analytical techniques as well as single crystal X-ray diffraction study. • CdS nanospheres ( CdS-1/2 ) were prepared by controlled solid-state thermolysis using of 1 and 2 as precursors. • The photocatalytic activities of 1, 2, CdS-1 , and CdS-2 were evaluated for degradation of methylene blue under visible light. • In comparison to coordination polymers, the NPs have greater photocatalytic efficiency. Two coordination polymers [Cd(L) 2 (H 2 O) 2 ] n ( 1 ) and [Cd(L)-µ 2 Cl] n ( 2 ) are synthesized from a l -methinone based reduced Schiff base ligand and characterized by various spectrochemical and analytical methods along with single-crystal X-ray analysis. The crystal structures indicate formation of a one-dimensional (1D) and a three-dimensional (3D) framework for 1 and 2 respectively. Controlled solid-state thermolysis of 1 and 2 , resulted size specific CdS nanospheres ( CdS-1/2 ) having hexagonal wurtzite structure with excellent optical properties. The photocatalytic activities of coordination polymers ( 1 / 2 ) as well as nanoparticles ( CdS-1/2) are evaluated in degradation of methylene blue (MB) solution in presence of visible light which shows enhanced catalytic efficiency of nanoparticles over coordination polymers. Catalytic efficacy and reusability suggest the synthesized nanospheres can be used as potential photocatalysts for removal of hazardous organic wastes from water.

Inorganic Metal-Oxide Photocatalyst for H2 O2 Production.

Hydrogen peroxide (H2 O2 ) is a mild but versatile oxidizing agent with extensive applications in bleaching, wastewater purification, medical treatment, and chemical synthesis. The state-of-art H2 O2 production via anthraquinone oxidation is hardly considered a cost-efficient and environment-friendly process because it requires high energy input and generates hazardous organic wastes. Photocatalytic H2 O2 production is a green, sustainable, and inexpensive process which only needs water and gaseous dioxygen as the raw materials and sunlight as the power source. Inorganic metal oxide semiconductors are good candidates for photocatalytic H2 O2 production due to their abundance in nature, biocompatibility, exceptional stability, and low cost. Progress has been made to enhance the photocatalytic activity toward H2 O2 production, however, H2 O2 photosynthesis is still in the laboratory research phase since the productivity is far from satisfaction. To inspire innovative ideas for boosting the H2 O2 yield in photocatalysis, the most well-studied metal oxide photocatalysts are selected and the modification strategies to improve their activity are listed. The mechanisms for H2 O2 production over modified photocatalysts are discussed to highlight the facilitating role of the modification methods. Besides, methods for the quantification of H2 O2 and associated radical intermediates are provided to guide future studies in this field.