In the present study, the novel Ag/cellulose nanocrystal (CNC)-doped CeO2 quantum dots (QDs) with highly efficient catalytic performance were synthesized using one pot co-precipitation technique, which were then applied in the degradation of methylene blue and ciprofloxacin (MBCF) in wastewater. Catalytic activity against MBCF dye was significantly reduced (99.3%) for (4%) Ag dopant concentration in acidic medium. For Ag/CNC-doped CeO2 vast inhibition domain of G-ve was significantly confirmed as (5.25-11.70 mm) and (7.15-13.60 mm), while medium- to high-concentration of CNC levels were calculated for G + ve (0.95 nm, 1.65 mm), respectively. Overall, (4%) Ag/CNC-doped CeO2 revealed significant antimicrobial activity against G-ve relative to G + ve at both concentrations, respectively. Furthermore, in silico molecular docking studies were performed against selected enzyme targets dihydrofolate reductase (DHFR), dihydropteroate synthase (DHPS), and DNA gyrase belonging to folate and nucleic acid biosynthetic pathway, respectively to rationalize possible mechanism behind bactericidal potential of CNC-CeO2 and Ag/CNC-CeO2.
Toxic elements in drinking water have great effects on human health. However, there is very limited information about toxic elements in drinking water in Afghanistan. In this study, levels of 10 elements (chromium, nickel, copper, arsenic, cadmium, antimony, barium, mercury, lead and uranium) in 227 well drinking water samples in Kabul, Afghanistan were examined for the first time. Chromium (in 0.9% of the 227 samples), arsenic (7.0%) and uranium (19.4%) exceeded the values in WHO health-based guidelines for drinking-water quality. Maximum chromium, arsenic and uranium levels in the water samples were 1.3-, 10.4- and 17.2-fold higher than the values in the guidelines, respectively. We next focused on uranium, which is the most seriously polluted element among the 10 elements. Mean ± SD (138.0 ± 1.4) of the (238)U/(235)U isotopic ratio in the water samples was in the range of previously reported ratios for natural source uranium. We then examined the effect of our originally developed magnesium (Mg)-iron (Fe)-based hydrotalcite-like compounds (MF-HT) on adsorption for uranium. All of the uranium-polluted well water samples from Kabul (mean ± SD = 190.4 ± 113.9 μg/L; n = 11) could be remediated up to 1.2 ± 1.7 μg/L by 1% weight of our MF-HT within 60 s at very low cost (<0.001 cents/day/family) in theory. Thus, we demonstrated not only elevated levels of some toxic elements including natural source uranium but also an effective depurative for uranium in well drinking water from Kabul. Since our depurative is effective for remediation of arsenic as shown in our previous studies, its practical use in Kabul may be encouraged.
Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.
This study investigated the removal of parabens, N,N-diethyl-m-toluamide (DEET), and phthalates by ozonation. The second-order rate constants for the reaction between selected compounds with ozone at pH 7 were of (2.2 +/-0.2) X 10(6) to (2.9 +/-0.3) X 10(6) M 1/s for parabens, (2.1+/- 0.3) to (3.9 +/-0.5) M-1/s for phthalates, and (5.2 +/-0.3) M-1/s for DEET. The rate constants for the reaction between selected compounds with hydroxyl radical ranged from (2.49 +/-0.06) x 10(9) to (8.5 +/-0.2) x 10(9) M-1/s. Ozonation of selected compounds in secondary wastewater and surface waters revealed that ozone dose of 1 and 3 mg/L yielded greater than 99% depletion of parabens and greater than 92% DEET and phthalates, respectively. In addition, parabens were found to transform almost exclusively through the reaction with ozone, while DEET and phthalates were transformed almost entirely by hydroxyl radicals (.OH).
The adsorption of methylene blue (MB) from aqueous solution using a low-cost adsorbent, rejected tea (RT), has been studied by batch adsorption technique. The adsorption experiments were carried out under different conditions of initial concentration (50-500 mg/L), solution pH 3-12, RT dose (0.05-1g) and temperature (30-50 degrees C). The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model with maximum monolayer adsorption capacities found to be 147, 154 and 156 mg/g at 30, 40 and 50 degrees C, respectively. Three kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion were employed to describe the adsorption mechanism. The experimental results showed that the pseudo-second-order equation is the best model that describes the adsorption behavior with the coefficient of correlation R(2)>or=0.99. The results suggested that RT has high potential to be used as effective adsorbent for MB removal.
Oil palm fronds (OPF) were used to prepare activated carbon (PFAC) using physiochemical activation method, which consisted of potassium hydroxide (KOH) treatment and carbon dioxide gasification. The effects of the preparation variables, which were activation temperature, activation time and chemical impregnation ratios (KOH: char by weight), on the carbon yield and bentazon removal were investigated. Based on the central composite design (CCD), two factor interaction (2FI) and quadratic models were, respectively, employed to correlate the PFAC preparation variables to the bentazon removal and carbon yield. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The optimum conditions for preparing activated carbon from OPF were found as follows: activation temperature of 850 degrees C, activation time of 1h and KOH:char ratio of 3.75:1. The predicted and experimental results for removal of bentazon and yield of PFAC were 99.85%, 20.5 and 98.1%, 21.6%, respectively.
The effects of Mecoprop (RS)-MCPP were investigated in an anaerobic membrane bioreactor (AnMBr) fed with synthetic wastewater containing stepwise increases in Mecoprop concentration, 5-200 mg L(-1) over 240 days. Effects were observed in terms of soluble chemical oxygen demand (COD) removal efficiency, volatile fatty acid (VFA) production, and methane yield. Soluble COD removal efficiency was stable at Mecoprop concentrations below 200 (±3) mg L(-1), with an average of 98 (±0.7)% removal. However, at 200 (±3) mg L(-1) Mecoprop, the COD removal efficiency decreased gradually to 94 (±1.5)%. At 5 mg L(-1) Mecoprop, acetic and propionic acid concentrations increased by 60% and 160%, respectively. In contrast, when Mecoprop was increased to 200 (±3) mg L(-1), the formation and degradation of acetate was unaffected by the higher Mecoprop concentration, acetate remaining below 35 mg L(-1). Increases in the Mecoprop specific utilization rate were observed as Mecoprop was increased stepwise between 5 and 200 mg L(-1).
The influence of TiO2 nanoparticles (TiO2-NPs) (10-50mg/L) on aerobic granulation of algal-bacterial symbiosis system was investigated by using two identical sequencing batch reactors (SBRs). Although little adverse effect was observed on their nitritation efficiency (98-100% in both reactors), algal-bacterial granules in the control SBR (Rc) gradually lost stability mainly brought about by algae growth. TiO2-NPs addition to RT was found to enhance the granulation process achieving stable and compact algal-bacterial granules with remarkably improved nitratation thus little nitrite accumulation in RT when influent TiO2-NPs⩾30mg/L. Despite almost similar organics and phosphorus removals obtained in both reactors, the stably high nitratation efficiency in addition to much stable granular structure in RT suggests that TiO2-NPs addition might be a promising remedy for the long-term operation of algal-bacterial granular system, most probably attributable to the stimulated excretion of extracellular polymeric substances and less filamentous TM7.
Environmental contamination by petroleum hydrocarbons, mainly crude oil waste from refineries, is becoming prevalent worldwide. This study investigates the bioremediation of water contaminated with crude oil waste. Bacillus salamalaya 139SI, a bacterium isolated from a private farm soil in the Kuala Selangor in Malaysia, was found to be a potential degrader of crude oil waste. When a microbial population of 108 CFU ml-1 was used, the 139SI strain degraded 79% and 88% of the total petroleum hydrocarbons after 42 days of incubation in mineral salt media containing 2% and 1% of crude oil waste, respectively, under optimum conditions. In the uninoculated medium containing 1% crude oil waste, 6% was degraded. Relative to the control, the degradation was significantly greater when a bacteria count of 99 × 108 CFU ml-1 was added to the treatments polluted with 1% oil. Thus, this isolated strain is useful for enhancing the biotreatment of oil in wastewater.
Phosphoric acid impregnated activated carbon from date pits (DPAC) was prepared through single step activation. Prepared DPAC was studied for its structural, elemental, chemical, surface and crystal nature. Adsorption ability of the DPAC was assessed through divalent lead ions separation studies. Effect of adsorbent dosage, contact time, pH, operating temperature and initial feed concentration on lead removal by DPAC was studied. Maximum Pb(II) adsorption capacity of 101.35 mg/g was attained for a contact time of 30 min and pH of 6 at 30°C. Increase in initial feed concentration enhanced the adsorption ability of DPAC and the rise in adsorbent dosage resulted in improved Pb(II) removal efficiency. Thermodynamic studies revealed that the lead adsorption on DPAC was exothermic and instantaneous in nature. Kinetic and equilibrium studies confirmed the suitability of pseudo-second order and Langmuir isotherm for divalent lead ions binding on DPAC. Reusability studies showed that HCl was the effective regeneration medium and the DPAC could be reused for a maximum of 4 times with slight reduction in Pb(II) removal efficiency (<10%). Results indicated the promising use of date pits biomass as a low cost and efficient starting material to prepare activated carbon for divalent lead ions removal.
Rice husk is a base adsorbent for pollutant removal. It is a cost-effective material and a renewable resource. This study provides the physicochemical characterization of chemically and thermally treated rice husk adsorbents for phenol removal from aqueous solutions. We revealed new functional groups on rice husk adsorbents by Fourier transform infrared spectroscopy, and observed major changes in the pore structure (from macro-mesopores to micro-mesopores) of the developed rice husk adsorbents using scanning electron microscopy. Additionally, we studied their surface area and pore size distribution, and found a greater enhancement of the morphological structure of the thermally treated rice husk compared with that chemically treated. Thermally treated adsorbents presented a higher surface area (24-201 m2.g-1) than those chemically treated (3.2 m2.g-1). The thermal and chemical modifications of rice husk resulted in phenol removal efficiencies of 36%-64% and 28%, respectively. Thus, we recommend using thermally treated rice husk as a promising adsorbent for phenol removal from aqueous solutions.
The natural coagulant Moringa oleifera lectin (MoL) as cationic protein is a promising candidate in coagulation process of water treatment plant. Introducing the gene encoding MoL into a host, Pichia pastoris, to secrete soluble recombinant protein is assessed in this study. Initial screening using PCR confirmed the insertion of MoL gene, and SDS-PAGE analysis detected the MoL protein at 8 kDa. Cultured optimization showed the highest MoL protein at 520 mg/L was observed at 28 °C for 144 h of culturing by induction in 1% methanol. Approximately, 0.40 mg/mL of recombinant MoL protein showed 95 ± 2% turbidity removal of 1% kaolin suspension. In 0.1% kaolin suspension, the concentration of MoL at 10 μg/mL exhibits the highest turbidity reduction at 68 ± 1%. Thus, recombinant MoL protein from P. pastoris is an effective coagulant for water treatment.
Bio-hydrogen production from wastewater using sludge as inoculum is a sustainable approach for energy production. This study investigated the influence of initial pH and temperature on bio-hydrogen production from dairy wastewater using pretreated landfill leachate sludge (LLS) as an inoculum. The maximum yield of 113.2 ± 2.9 mmol H2/g chemical oxygen demand (COD) (12.8 ± 0.3 mmol H2/g carbohydrates) was obtained at initial pH 6 and 37 °C. The main products of volatile fatty acids were acetate and butyrate with the ratio of acetate:butyrate was 0.4. At optimum condition, Gibb's free energy was estimated at -40 kJ/mol, whereas the activation enthalpy and entropy were 65 kJ/mol and 0.128 kJ/mol/l, respectively. These thermodynamic quantities suggest that bio-hydrogen production from dairy wastewater using pretreated LLS as inoculum was effective and efficient. In addition, genomic and bioinformatics analyses were performed in this study.
The adsorption behavior of basic, methylene blue (MB), and reactive, remazol brilliant violet 5R (RBV), dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon (IBSAC) was executed via batch and column studies. The produced activated carbon was characterized through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch studies were performed to investigate the effects of contact time, initial concentration, and solution pH. The equilibrium data for both MB and RBV adsorption better fits Langmuir model with maximum adsorption capacity of 434.78 and 212.77 mg/g, respectively. Kinetic studies for both MB and RBV dyes showed that the adsorption process followed a pseudo-second-order and intraparticle diffusion kinetic models. For column mode, the breakthrough curves were plotted by varying the flow rate, bed height, and initial concentration and the breakthrough data were best correlated with the Yoon-Nelson model compared to Thomas and Adams-Bohart model. The adsorption activity of IBSAC shows good stability even after four consecutive cycles.
The conventional treatment process of palm oil mill effluent (POME) produces a highly colored effluent. Colored compounds in POME cause reduction in photosynthetic activities, produce carcinogenic by-products in drinking water, chelate with metal ions, and are toxic to aquatic biota. Thus, failure of conventional treatment methods to decolorize POME has become an important problem to be addressed as color has emerged as a critical water quality parameter for many countries such as Malaysia. Aspergillus fumigatus isolated from POME sludge was successfully grown in POME supplemented with glucose. Statistical optimization studies were conducted to evaluate the effects of the types and concentrations of carbon and nitrogen sources, pH, temperature, and size of the inoculum. Characterization of the fungus was performed using scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and Brunauer, Emmet, and Teller surface area analysis. Optimum conditions using response surface methods at pH 5.7, 35 °C, and 0.57 % w/v glucose with 2.5 % v/v inoculum size resulted in a successful removal of 71 % of the color (initial ADMI of 3,260); chemical oxygen demand, 71 %; ammoniacal nitrogen, 35 %; total polyphenolic compounds, 50 %; and lignin, 54 % after 5 days of treatment. The decolorization process was contributed mainly by biosorption involving pseudo-first-order kinetics. FTIR analysis revealed that the presence of hydroxyl, C-H alkane, amide carbonyl, nitro, and amine groups could combine intensively with the colored compounds in POME. This is the first reported work on the application of A. fumigatus for the decolorization of POME. The present investigation suggested that growing cultures of A. fumigatus has potential applications for the decolorization of POME through the biosorption and biodegradation processes.
Reactive dyes account for one of the major sources of dye wastes in textile effluent. In this study, decolorization of the monoazo dye, Acid Orange 7 (AO7) by the Enterococcus faecalis strain ZL that isolated from a palm oil mill effluent treatment plant has been investigated. Decolorization efficiency of azo dye is greatly affected by the types of nutrients and the size of inoculum used. In this work, one-factor-at-a-time (method and response surface methodology (RSM) was applied to optimize these operational factors and also to study the combined interaction between them. Analysis of AO7 decolorization was done using Fourier transform infrared (FTIR) spectroscopy, desorption study, UV-Vis spectral analysis, field emission scanning electron microscopy (FESEM), and high performance liquid chromatography (HPLC). The optimum condition via RSM for the color removal of AO7 was found to be as follows: yeast extract, 0.1% w/v, glycerol concentration of 0.1% v/v, and inoculum density of 2.5% v/v at initial dye concentration of 100 mg/L at 37 °C. Decolorization efficiency of 98% was achieved in only 5 h. The kinetic of AO7 decolorization was found to be first order with respect to dye concentration with a k value of 0.87/h. FTIR, desorption study, UV-Vis spectral analysis, FESEM, and HPLC findings indicated that the decolorization of AO7 was mainly due to the biosorption as well as biodegradation of the bacterial cells. In addition, HPLC analyses also showed the formation of sulfanilic acid as a possible degradation product of AO7 under facultative anaerobic condition. This study explored the ability of E. faecalis strain ZL in decolorizing AO7 by biosorption as well as biodegradation process.
In this present study, adsorptive membranes for Cr(VI) ion removal were prepared by blending polyethersulfone (PES) with hydrous ferric oxide (HFO) nanoparticles (NPs). The effects of HFO NPs to PES weight ratio (0-1.5) on the physicochemical properties of the resultant HFO/PES adsorptive membranes were investigated with respect to the surface chemistry and roughness as well as structural morphologies using different analytical instruments. The adsorptive performance of the HFO NPs/PES membranes was studied via batch adsorption experiments under various conditions by varying solution pH, initial concentration of Cr(VI), and contact time. The results showed that the membrane made of HFO/PES at a weight ratio of 1.0 exhibited the highest adsorption capacity which is 13.5 mg/g. Isotherm and kinetic studies revealed that the mechanism is best fitted to the Langmuir model and pseudo-second-order model. For filtration of Cr(VI), the best promising membranes showed improved water flux (629.3 L/m2 h) with Cr(VI) ion removal of 75%. More importantly, the newly developed membrane maintained the Cr(VI) concentration below the maximum contamination level (MCL) for up to 9 h.
Biological aerated filter (BAF), sand filtration (SF), alum and Moringa oleifera coagulation were investigated as a pre-treatment for reducing the organic and biofouling potential component of an ultrafiltration (UF) membrane in the treatment of lake water. The carbohydrate content was mainly responsible for reversible fouling of the UF membrane compared to protein or dissolved organic carbon (DOC) content. All pre-treatment could effectively reduce these contents and led to improve the UF filterability. Both BAF and SF markedly led to improvement in flux than coagulation processes, and alum gave greater flux than M. oleifera. This was attributed to the effective removal and/or breakdown of high molecular weight (MW) organics by biofilters. BAF led to greater improvement in flux than SF, due to greater breakdown of high MW organics, and this was also confirmed by the attenuated total reflection-Fourier transform infrared spectroscopy analysis. Coagulation processes were ineffective in removing biofouling potential components, whereas both biofilters were very effective as shown by the reduction of low MW organics, biodegradable dissolved organic carbon and assimilable organic carbon contents. This study demonstrated the potential of biological pre-treatments for reducing organic and biofouling potential component and thus improving flux for the UF of lake water treatment.
The ash of C. polygonoides (locally called balanza) was collected from Lakki Marwat, Khyber Pakhtunkhwa, Pakistan, and was utilized as biosorbent for methylene blue (MB) removal from aqueous solution. The ash was used as biosorbent without any physical or chemical treatment. The biosorbent was characterized by using various techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The particle size and surface area were measured using particle size analyzer and Brunauer-Emmett-Teller equation (BET), respectively. The SEM and BET results expressed that the adsorbent has porous nature. Effects of various conditions such as initial concentration of methylene blue (MB), initial pH, contact time, dosage of biosorbent, and stirring rate were also investigated for the adsorption process. The rate of the adsorption of MB on biomass sample was fast, and equilibrium has been achieved within 1 hour. The kinetics of MB adsorption on biosorbent was studied by pseudo-first- and pseudo-second-order kinetic models and the pseudo-second-order has better mathematical fit with correlation coefficient value (R (2)) of 0.999. The study revealed that C. polygonoides ash proved to be an effective, alternative, inexpensive, and environmentally benign biosorbent for MB removal from aqueous solution.
Effluent containing colour/dyes, especially reactive dyes, becomes a great concern of wastewater treatment because it is toxic to human life and aquatic life. In this study, reactive dye of Black B was separated using the supported liquid membrane process. Commercial polypropylene membrane was used as a support of the kerosene-tridodecylamine liquid membrane. Several parameters were tested and the result showed that almost 100% of 70 ppm Black B was removed and 99% of 70 ppm Black B was recovered at pH 2 of the feed phase containing 0.00001 M Na2SiO3, flow rate of 150 ml/min and 0.2 M NaOH. The membrane support also remained stable for up to 36 hours under an optimum condition.