Photocatalytic Degradation Studies of Organic Dyes over Novel Cu/Ni Loaded Reduced Graphene Oxide Hybrid Nanocomposite: Adsorption, Kinetics and Thermodynamic Studies.

Nowadays, for environmental remediation, photocatalytic process involving graphene-based semiconductors is considered a very promising oxidation process for water treatment. In the present study, nanocomposite (Cu/Ni/rGO) has been synthesized by Dypsis lutescens leaf extract. Characterization of the sample was carried out by UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Different parameters like contact time, nanocatalyst amount, dye concentration, effect of temperature. and pH factor were optimized to examine the maximum removal efficiency for dyes rhodamine B and alizarine R with and without visible light source. In both cases, i.e., with or without light, maximum removal was observed at 20 mg of nanocatalyst for 5 ppm concentration of both dyes at 45 °C temperature and pH 10 for rhodamine B and pH 4 for alizarine R, respectively with a 20 min contact time. Maximum removal of dyes 93% rhodamine B and 91% alizarine R were observed under a tungsten lamp as compared to without a tungsten lamp, i.e., 78% of RhB and 75% of AR from mixture solution of these dyes. To assess the rate of reaction, spontaneity, and nature of reaction thermodynamics, kinetics and adsorption isotherms were studied. Thermodynamic values indicated that both dyes depicted endothermic and spontaneous degradation processes. Isotherm data fitted best to a Freundlich isotherm, while results of kinetic studies of both dyes followed the pseudo 2nd order kinetic equation. In the end, scavenging radical studies concluded that hydroxyl radicals were the main active specie involved in the photocatalytic degradation process, and regeneration experiments resulted that Cu/Ni/rGO nanocomposites were re-utilized for about four times.

Investigating the role of bulking agents in compost maturity.

Kitchen waste is increasing globally, similarly in Pakistan bulk of municipal solid waste comprises of kitchen waste specifically, tea waste. Composting of kitchen waste is one of the promising ways to convert waste into useful product, resulting into zero waste. This study is aimed to convert waste (kitchen waste) in to a resource (compost) using bulking agents (tea waste and biochar) for reducing maturity time. Secondly, compost application on Solanum lycopersicum (tomato) was also tested. Four compost treatments were designed under aerobic composting conditions for 30 days. Tea waste and biochar have accelerated the maturity rate and produced a nutrient rich compost. Final compost had Electrical Conductivity of 2mS/cm, Carbon Nitrogen ration of 15, 54% of organic matter, 15% of moisture content, 48% of cellulose content, and 28% of Lignin content. With the use of Co-compost the Solanum lycopersicum showed 133% germination index, 100% germination, 235% Munoo-Liisa Vitality Index and 1238% seed vigor index. Co-compost also improved the soil total nitrogen by 1.4%, total phosphorous by 2%, total potassium by 2.1% and bulk density by 2.6 gcm-3. This study successfully used tea waste and biochar as bulking agents to reduce maturation time to 30 days. Tea waste and biochar enhanced the organic matter degradation, lignocellulose degradation, water holding capacity, porosity, seed's vigor, germination index. This research can be helpful in developing home composting and home gardening to combat solid waste management and food security issue in developing countries.

Biodegradation of chlorpyrifos using isolates from contaminated agricultural soil, its kinetic studies.

Extensive pesticides use is negatively disturbing the environment and humans. Pesticide bioremediation with eco-friendly techniques bears prime importance. This study evaluates the bioremediation of chlorpyrifos in soil using indigenous Bacillus cereus Ct3, isolated from cotton growing soils. Strains were identified through ribotyping (16s rRNA) by Macrogen (Macrogen Inc. Geumchen-gu, South Korea). Bacillus cereus Ct3 was resistant up to 125 mg L-1 of chlorpyrifos and successfully degraded 88% of chlorpyfifos in 8 days at pH 8. Bacillus cereus Ct3 tolerated about 30-40 °C of temperature, this is a good sign for in situ bioremediation. Green compost, farmyard manure and rice husk were tested, where ANOVA (P < 0.05) and Plackett-Burman design, results indicated that the farm yard manure has significant impact on degradation. It reduced the lag phase and brought maximum degradation up to 88%. Inoculum size is a statistically significant (P < 0.05) factor and below 106 (CFU g-1) show lag phase of 4-6 days. Michaelis-Menten model results were as follows; R2 = 0.9919, Vmax = 18.8, Ks = 121.4 and Vmax/Ks = 0.1546. GC-MS study revealed that chlorpyrifos first converted into diethylthiophosphoric acid and 3,5,6-trichloro-2-pyridinol (TCP). Later, TCP ring was broken and it was completely mineralized without any toxic byproduct. Plackett-Burman design was employed to investigate the effect of five factors. The correlation coefficient (R2) between experimental and predicted value is 0.94. Central composite design (CBD) was employed with design matrix of thirty one predicted and experimental values of chlorpyrifos degradation, having "lack of fit P value" of "0.00". The regression coefficient obtained was R2 = 0.93 which indicate that the experimental vales and the predicted values are closely fitted. The most significant factors highlighted in CBD/ANOVA and surface response plots were chlorpyrifor concentration and inoculum size. Bacillus cereus Ct3 effectively degraded chlorpyrifos and can successfully be used for bioremediation of chlorpyrifos contaminated soils.

Effect of industrial wastewater on wheat germination, growth, yield, nutrients and bioaccumulation of lead.

Due to fresh water scarcity, farmers are using polluted water for irrigation. This research was conducted to study the bioaccumulation of Pb in wheat (Cv. Shafaq-2006). The experiment was comprised of seven treatments of lead i.e. 0-1,000 mg Pb/kg. The results revealed that lead severely reduces germination (- 30%), seedling fresh weight (- 74%), seedling dry weight (- 77%), vigor index (- 89%), tolerance index (- 84%), plant height (- 33%), number of leaves (- 41%), root fresh weight (- 50%), shoot fresh weight (- 62%), root dry weight (- 63%), shoot dry weight (- 71%), and root length (- 45%). The physiological parameters also respond negatively like stomatal conductance (- 82%), transpiration rate (- 72%) and photosynthetic rate (- 74%). Similarly, biochemical parameters also showed negative impacts, like carotenoids (- 41), total chlorophyll (- 43), chlorophyll a (- 42) and chlorophyll b (- 53). Yield parameters like the number of seed/plant, seed weight/plant, 1,000 seed weight and harvest index were reduced by 90%, 88%, 44% and 61%, respectively in T6. In addition, protein contents (- 81%), phosphorous (- 60%) and potassium (- 55%) were highly effected in the highest lead concentration (T6). Lead accumulation was extremely higher in seeds (119%) as compared to control plants. Lead bio-accumulation above threshold concentrations in crop parts is a serious human health concern.

Heavy metal phytoextraction potential of indigenous tree species of the family fabaceae.

Untreated industrial wastewater (IWW) creates a number of problems in ecosystem. This study highlights the possibility of using IWW for forest irrigation. Five tree species were selected for this study, Albizia lebbeck, Bauhinia purpurea, Dalbergia sissoo, Millettia peguensis, and Pongamia pinnata, and these species were grown in pots and were irrigated with different concentrations of IWW, rich in heavy metals. All the species showed positive results for fresh weight, plant height, and stem diameter. The maximum proline content was observed in B. purpurea (6.33), whereas the least quantity was observed in P. pinnata (3.89). Lead uptake (163.801 mg/day) by B. purpurea was promising. Uptake of Cr and Cu was slow in all species. Translocation factor of D. sissoo was maximum, that is 3.37. This study successfully combats wastewater problem. These five species are much tolerant in IWW and can be successfully used for phytoextraction processes. The chromium accumulation in stem is as follows: D. sissoo > A. lebbeck > M. peguensis > P. pinnata > B. purpurea. Metal Bioaccumulation in leaf and root was less. The idea is to utilize IWW to generate urban forests (in eco-friendly and sustainable way), which can reduce multiple problems such as IWW toxicity and air pollution through urban forestry.