Initial Pollutant Concentration Research Articles

Removal of chromium (VI) ions from aqueous solutions

The object of the research is the flotoextraction of chromium (VI) ions from model and real waste waters. Hexavalent chromium compounds pose a serious hazard to surface and ground waters and can have mutagenic and carcinogenic effects on living organisms. The study of the process of flotoextraction as a method of purifying waste water from heavy metals using the example of chromium (VI) ions is an important task. The paper considers flotoextraction of chromium (VI) ions using a cationic surfactant – hexadecylpyridinium chloride and butyl alcohol as the organic phase. The dependences of the process efficiency on the presence of a cationic surfactant, the flotoextraction time, the type of organic extractant, the nature of the collector and the surfactant: Cr molar ratio, the initial concentration of pollutants, and the pH of the initial solution were obtained. Certain rational conditions for flotation allow removing 98–99.6 % of pollutants. The method was tested on real wastewater. The importance of this study is emphasized by the fact that flotoextraction has a number of features and advantages. In particular, the possibility of multiple concentration of pollutant ions in small volumes of an organic solvent and the possibility of its further regeneration. In this case, a much smaller amount of an organic solvent is used and the process is not limited by the distribution constant (compared to the extraction method). Flotoextraction is also characterized by the absence of foam (compared to the flotation method) and the absence of large amounts of wet sludge (compared to the reagent method). The proposed method provides a sufficient level of chromium ions removal from wastewater, and can also be used in systems for local wastewater treatment with the subsequent return of water to the technological process. This will ensure a reduction in costs for the consumption of water resources, discharge of wastewater into water bodies, and also limit the ingress of harmful substances into the environment.

Enhancing the visible-light photoactivity of silica-supported TiO2 for the photocatalytic treatment of pharmaceuticals in water.

Catalyst samples based on SiO2-supported TiO2 were prepared with the incorporation of Ag (metal), S (nonmetal), and ZnO@S (semiconductor and nonmetal). The materials were evaluated regarding their morphological, optical, and crystalline properties as well as their photoactivity under visible and ultraviolet light toward the degradation rate of a model emerging pollutant, acetaminophen (ACT). All modified materials exhibited improved performance over the undoped catalyst. The Ag-doped catalyst achieved the largest degradation under visible radiation (about 30% in 120 min), whereas under ultraviolet irradiation, the ZnO@S-doped sample exhibited the best performance (about 62% in 120 min). A Doehlert design was carried out to evaluate the influence of pH and temperature on the photoactivity of Ag-TiO2/SiO2. In addition, the role of each reactive species in the photodegradation reaction was investigated by radical scavenger experiments, and the superoxide radical anion O2•- was shown to be the predominant reactive species. The stability of the Ag-TiO2/SiO2 material under ultraviolet and visible light was confirmed after five successive operation cycles, showing a reasonable (about 50%) loss of activity under visible irradiation and a slight improvement (about 13%) under UV light, as a result of the photo-reduction of Ag+. Lastly, the effect of the initial pollutant concentration showed that ACT degradation using Ag-TiO2/SiO2 follows the Langmuir-Hinshelwood kinetics, with intrinsic reaction rate k = 2.71 × 10-4 mmol L-1 min-1under visible-light radiation.

H-Clinoptilolite as an Efficient and Low-Cost Adsorbent for Batch and Continuous Gallium Removal from Aqueous Solutions

In this paper, the gallium (III) ions’ adsorption onto protonated clinoptilolite (H-CLP) was investigated both in batch and fixed-bed column experiments. Regarding batch experiments, the influence of some parameters such as adsorbent dosage, size particle, and temperature was studied, determining that a dosage of 10 g/L for an initial pollutant concentration of 40 mg/L leads to a removal percentage over 85% regardless of particle size and temperature. On the other hand, adsorption of gallium onto H-CPL is an endothermic and spontaneous process in the studied temperature range, concluding that the maximum adsorption capacity was 16 mg/g for 60 °C. Concerning to the effect of the presence of other cations in solution, such as Na+, K+, or Ca2+, gallium adsorption capacity only drops by 20%, although the initial concentration of other cations in the solution is 50 times higher than gallium concentration. This means that clinoptilolite has a high affinity for gallium which can be very favorable for further selectivity tests. A crucial factor for this high selectivity could be the protonation of clinoptilolite which allows working without modifying the pH of the aqueous solution with acid. In the fixed-bed experiments, breakthrough curves were obtained, and the effect of operation variables was determined. A breakpoint value of 254 min for 64 g of adsorbent and flow rate of 9.0 mL/min (7.0 BV/h) were obtained, when treating a pollutant volume of 33 BV. Additionally, the breakthrough curves were fitted to different models to study the particle size effect, being the best fit corresponding to the Adams–Bohart model. This fact confirmed the influence of particle size on adsorption kinetics.Graphical

Ferrocene modified g-C3N4 as a heterogeneous catalyst for photo-assisted activation of persulfate for the degradation of tetracycline

In this study, the oxidative degradation of tetracycline (TC) by ferrocene-modified graphite phase carbon nitride (Fe/g-C 3 N 4 ) activated persulfate (PS) under light-assisted conditions is examined. The materials are characterized by a series of methods such as SEM, TEM, XRD, FTIR, XPS, etc. This article explores the influence of the amount of sulfate, the initial concentration of pollutants, the amount of catalyst, and the pH value on the reaction system. When the amount of PS added reaches 2.5 mM and the catalyst dosage is 1 g L −1 , the Fe/g-C 3 N 4 /PS/Vis exhibit the best performance for tetracycline removal. In 60 min, the removal of tetracycline reaches 93% under its natural pH. In the reaction system acidic neutral conditions are more conducive to degrade TC. The results show that the doping of ferrocene inhibits the recombination of electron-hole pairs in the g-C 3 N 4 , expands the light response range to speed up the removal rate of tetracycline. At the same time, iron cycle generated by ferrocene modification helps to activate persulfate to produce sulfate radicals with strong oxidizing properties. Sulfate radicals, hydroxyl radicals, superoxide radicals and holes are the main active species proved by ESR test and the quenching experiments. The synergy between photocatalysis and PS activation promotes the production of active species and the tetracycline removal. The results show that the Fe/g-C 3 N 4 composite material activated persulfate under visible light is an effective method to remove tetracycline from water. In this paper, the synthesis of ferrocene doped graphite phase carbon nitride and the removal of tetracycline in water by activated persulfate are mainly introduced.

Synthesis of EDTA-functionalized graphene oxide-chitosan nanocomposite for simultaneous removal of inorganic and organic pollutants from complex wastewater

Discharging of inorganic and organic pollutants creates a serious threat to the human health and the environment. In the current work, we have synthesized Ethylenediaminetetraacetic acid (EDTA) functionalized graphene oxide-chitosan nanocomposite (GO-EDTA-CS) for simultaneous removal of inorganic (i.e., mercury (Hg(II) and copper (Cu(II)) and organic pollutants (i.e., methylene blue (MB) and crystal violet (CV)) from wastewater via adsorption process. The structural, functional, morphological, elemental compositions, surface area and thermal properties of the synthesized nanocomposite were identified using powder X−ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), Brunauer−Emmett−Teller (BET), and thermogravimetric analyzer (TGA), respectively. Different batch adsorption experiments such as pH effect, contact time, initial pollutants concentration, reusability etc. were studied in monocomponent system to optimize the results. The adsorption process apparently followed pseudo−second−order (PSO) kinetics for both pollutants, however the adsorption kinetics was also explained by the intra−particle diffusion model. The isotherm data for both metals ions and dyes were well fit by the Langmuir isotherm model. The maximum adsorption capacities of the adsorbent were determined 324 ± 3.30 130 ± 2.80, 141 ± 6.60, and 121 ± 3.50 mg g−1 for Hg(II), Cu(II), MB, and CV, respectively. The excellent adsorption capacity was attributed to the availability of various active functional groups (e.g., –COOH, –OH, –NH2, etc.) on the adsorbent. The EDS, elemental mapping and FTIR analysis performed before and after the adsorption of heavy metals and dyes by GO-EDTA-CS confirmed the simultaneous adsorption of the pollutants. Moreover, GO-EDTA-CS could maintain its adsorption capacity for both inorganic and organic pollutants even after seven cycles of adsorption-desorption, indicating itself a promising adsorbent for practical wastewater treatment containing both inorganic and organic toxic pollutants.

Review On Activated Carbon: Synthesis, Properties And Applications

Many researchers have reported that a number of control methods were used in waste water treatment. In this work, there are several types of agricultural wastes and fruits were employed to synthesis activated carbon via chemical activation and physical activation process. The obtained activated carbons indicated higher surface area and larger adsorption capacity. This paper describes experimental findings on uses of activated carbon in wastewater treatment, which produced under different conditions such as contact time, initial pollutant concentration, temperature, pH value, adsorbent dosage, particle size and agitation. The adsorption capacity and equilibrium data of different pollutants (dyes, oil, grease waste water, organic pollutants, pesticides, herbicides, heavy metal ions, lignin and tannin colour) were studied through various isotherms. Thermodynamic parameters such as entropy, free energy and enthalpy were investigated.

Decontamination of emerging pharmaceutical pollutants using carbon-dots as robust materials

Environmental pollution is a critical issue that requires proper measures to maintain environmental health in a sustainable and effective manner. The growing persistence of several active pharmaceutical residues, such as antibiotics like tetracycline, and anti-inflammatory drugs like diclofenac in water matrices is considered an issue of global concern. Numerous sewage/drain waste lines from the domestic and pharmaceutical sector contain an array of toxic compounds, so-called “emerging pollutants” and possess adverse effects on entire living ecosystem and damage its biodiversity. Therefore, effective solution and preventive measures are urgently required to sustainably mitigate and/or remediate pharmaceutically active emerging pollutants from environmental matrices. In this context, herein, the entry pathways of the pharmaceutical waste into the environment are presented, through the entire lifecycle of a pharmaceutical product. There is no detailed review available on carbon-dots (CDs) as robust materials with multifunctional features that support sustainable mitigation of emerging pollutants from water matrices. Thus, CDs-based photocatalysts are emerging as an efficient alternative for decontamination by pharmaceutical pollutants. The addition of CDs on photocatalytic systems has an important role in their performance, mainly because of their up-conversion property, transfer photoinduced electron capacities, and efficient separation of electrons and holes. In this review, we analyze the strategies followed by different researchers to optimize the photodegradation of various pharmaceutical pollutants. In this manner, the effect of different parameters such as pH, the dosage of photocatalyst, amount of carbon dots, and initial pollutant concentration, among others are discussed. Finally, current challenges are presented from a pollution prevention perspective and from CDs-based photocatalytic remediation perspective, with the aim to suggest possible research directions.

Utilization of layered double hydroxides (LDHs) and their derivatives as photocatalysts for degradation of organic pollutants.

Direct or indirect discharge of wastes containing organic pollutants have contributed to the environmental pollution globally. Decontamination of highly polluted natural resources such as water using an effective treatment is a great challenge for public health and environmental protection. Photodegradation of organic pollutants using efficient photocatalyst has attracted extensive interest due to their stability, effectiveness towards degradation efficiency, energy, and cost efficiency. Among various photocatalysts, layered double hydroxides (LDHs) and their derivatives have shown great potential towards photodegradation of organic pollutants. Herein, we review the mechanism, key factors, and performance of LDHs and their derivatives for the photodegradation of organic pollutants. LDH-based photocatalysts are classified into three different categories namely unmodified LDHs, modified LDHs, and calcined LDHs. Each LDH category is reviewed separately in terms of their photodegradation efficiency and kinetics of degradation. In addition, the effect of photocatalyst dose, pH, and initial concentration of pollutant as well as photocatalytic mechanisms are also summarized. Lastly, the stability and reusability of different photocatalysts are discussed. Challenges related to modeling the LDHs and its derivatives are addressed in order to improve their functional capacity.

Enhanced Photocatalytic Degradation of Organic Pollutants Under Visible Light Using Ag-Modified TiO2 on Activated Carbon Fibers

Ag-modified TiO2 on activated carbon fibers (ACF) was synthesized and successfully used for the photocatalytic degradation of organic pollutants in this work. The physical properties of the materials were characterized using various methods such as X-ray diffraction, scanning electron microscope, Brunauer–Emmett–Teller, Fourier transform infrared, UV–Vis, electrochemical impedance spectroscopy and reusability tests. Besides, the effects of reaction parameters on photodegradation such as silver loading, light source, organic pollutant species and initial pollutant concentration were investigated. The results showed that Ag significantly increased the number of surface adsorption sites, improved the electron transmission rate and suppressed the complexation of e− and h[Formula: see text]. Under visible light, 1.5-Ag-TiO2/ACF [Formula: see text] revealed the best catalytic activity and reusability for dye removal and toluene adsorption. Based on the experimental results, a possible photocatalytic mechanism of Ag-TiO2/ACF was proposed. This study will provide a theoretical basis for the application of Ag-TiO2/ACF photocatalyst in the field of organic pollutants treatment.

Preparation of melamine-functionalized porous organic polymer and its adsorption properties for methyl orange

首先以对三联苯(TP)和对苯二甲酰氯(TC)为单体合成了酮基聚合物前体(TP-TC),而后基于席夫碱反应将三聚氰胺(MA)与之交联得到胺功能化的多孔有机聚合物TP-TC-MA。通过扫描电镜(SEM)、透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、氮气吸附-脱附(BET)以及零电荷点(pHpzc)的测定等手段对合成的多孔有机聚合物进行表征。以染料废水中典型的阴离子染料甲基橙为研究对象,研究了TP-TC-MA对其吸附行为,并探讨了吸附机制。利用紫外-可见分光光度计(UV-Vis)得出目标污染物的紫外吸收光谱标准曲线,标准曲线拟合相关系数(R2)为0.999。结果表明,TP-TC-MA由于具有高比表面积(708.5 m2/g)和总孔体积(0.556 cm3/g)以及丰富的含氮基团,对阴离子染料甲基橙表现出优异的吸附性能。TP-TC-MA对水中甲基橙的吸附动力学符合准二级动力学方程,吸附平衡数据可以采用Langmuir等温吸附模型描述。经由Langmuir等温吸附模型计算得到的理论最大吸附容量为156.3 mg/g。选择性实验结果表明,TP-TC-MA对阴离子染料甲基橙具有更强的吸附作用,吸附作用机理可归结为静电相互作用、氢键和π-π相互作用等。在重复使用5次之后,TP-TC-MA对甲基橙仍保持90%以上的去除率,表明材料具有良好的稳定性和重复利用性,在染料废水处理中具有很好的应用前景。

Cu2MoS4-based magnetic composites as effective adsorbent and photocatalyst for removal of organic contaminants in water

The wastewater containing pharmaceutical and personal care products (PPCPs) could not be removed effectively by traditional sewage treatment technologies and was directly discharged into the natural environment, causing serious threats to environment and human health. In this study, polypyrrole-functionalized Cu2MoS4 magnetic composites (Cu2MoS4-Fe3O4@PPy) were prepared and applied as an adsorbent for the removal of PPCPs from aqueous solution. Cu2MoS4-Fe3O4@PPy exhibited synergistic effects and showed excellent adsorption performances for indomethacin (IDM) and ketoprofen (KET) with removal efficiencies of 97.1% and 88.6% at initial pollutant concentration of 10 mg/L, respectively. It was also found that IDM and KET could be effectively removed by Cu2MoS4-Fe3O4@PPy in a wider pH range (5.0-11.0). Cu2MoS4-Fe3O4@PPy could be separated easily with a magnet and possessed the removal efficiency up to 83% even after eight adsorption-desorption cycles. Furthermore, the potential applications of Cu2MoS4-Fe3O4@PPy as a photocatalyst after the deposition of silver nanoparticles were further explored. Under visible-light irradiation, the Cu2MoS4-Fe3O4@PPy-Ag could quickly degrade malachite green (MG) with 94.8% removal within 60 min and had higher selectivity for MG in dual and ternary dye solutions. Due to excellent performances in adsorption and photocatalysis, Cu2MoS4-based magnetic composites had great potential application in the treatment of wastewater containing organic pollutants.

Phenol removal from aqueous solution using synthetic V-shaped organic adsorbent: Kinetics, isotherm, and thermodynamics studies

The utilization of a novel adsorbent Diphenyldiquinoline (DPDQ) were investigated for phenol elimination originating from a heavily polluted besmirched aquatic stage. The optimum adsorption conditions were included such as initial pollutant concentrations, reaction temperatures, and experimental duration. The initial pollutant concentration of 3 ppm, 25 °C reaction temperature, pH 4, and 15 min of adsorption duration was found to be optimum. The adsorption process was studied by Langmuir, Freundlich, and Temkin isotherm models, which demonstrated the Langmuir model to represent the process as compared to other models. The adsorption process followed as pseudo-second-order kinetics with rate constant (k) value of 0.288 g.mg−1.min.−1, and qe, qmax values of 23.26 and 15.15 mg/g, respectively. Moreover, all essential thermodynamic variables such as Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated. The overall outcome shows the efficiency of DPDQ in phenol adsorption and it may become a viable solution in the near future.

Removal of emerging pollutants from aquatic system using electrochemical treatment and adsorption: Comparison and analysis

The emerging pollutant such as metronidazole, chloramphenicol and sulphonamide were utilized for this research. Three-dimensional electrochemical reactor with particle electrodes such as Strychnos potatorum used to treat the above emerging pollutants. Voltage, pH, initial pollutant concentration and the particle electrode concentration were varied and the optimum conditions for the effective removal was found to be at 9 V, 15 grams of particle electrode and 100 mg/L of initial pollutant concentration. The efficiency of removal was found to be 93.68% for metronidazole, 94.56% for chloramphenicol and 94.11% for sulphonamide under optimum conditions. The air flow was varied to 2 L/min, 3 L/min and 5 L/min, the removal efficiency was found to be 80.24%, 94.12% and 95.26% for the above air flow rates. The comparison of adsorption, two-dimensional electrochemical treatment and three-dimensional electrochemical treatment was done and among them, three-dimensional electrochemical treatment was found to be 18.3% higher when compared to two-dimensional electrochemical treatment The removal efficiency for three-dimensional and two-dimensional treatment were found to be 53.74% and 45.83% in 60 min.

Photocatalytic Degradation of 2-propanol Over TiO2-based Thin Films in a Simulated Pilot Microreactor

Background: Microreactor devices have attracted increasing attention over the last years due to their high surface-to-volume ratio, which ensures a high heat and mass transfer, short molecular diffusion distance and greater spatial illumination homogeneity compared to the traditional reactors. Objective: The aim of this study was to model the kinetics of photo-degradation of 2-propanol over TiO2-based thin films in a gas-phase batch-reactor and simulate their performance in a microreactor device. Methods: The reaction was carried out in a gas-phase batch-reactor, assessing the reactivity of singlelayer nitrogen (N)-doped TiO2 and a bilayer consisting of N-doped TiO2 as a bottom layer and copper (Cu)-doped TiO2 as a top layer. The kinetics of the photocatalytic process was modelled by Langmuir– Hinshelwood (LH) model. The constants obtained from the LH model were used to simulate the performance of the photocatalysts in a microreactor, operating in a continuous flow mode and investigating the effect of the volumetric flow rate (Q), initial concentration of pollutant (Co), number of microchannels (n) and microchannel length (l) on the photo-degradation of 2-propanol. Results: N-Cu-TiO2 exhibited a higher reactivity but a lower adsorption ability towards the target pollutant compared to N-TiO2. To maximize and leverage the advantages of a microreactor, optimal operating conditions for a continuous flow mode, at a steady-state, should be moderately low Q and Co, long l and n that minimizes flow maldistribution in parallel. Conclusion: The findings in this work could serve as a basis to design and fabricate efficient microreactors for the removal of VOC in air purification applications.

Removal of agricultural wastewater pollutants by integrating two waste materials, fish scales and neem leaves, as novel potential adsorbent.

Only 2.5% of the world's water is fresh, despite the fact that water covers approximately 70% of the planet. This water is used for several recreational purposes and gets polluted by wastewater disposal directly into freshwater bodies. Effluents dispersed into water bodies could be from various sources like industries, households, and agricultural activities. These effluents comprise heavy metals and chemical wastes directly released into water bodies without treatment and could include major contaminants like nitrates, nitrites, ammonia and phosphates. The present study mainly focuses on removal of four significant pollutants from agriculture wastes, i.e., nitrates, nitrites, ammonia, and phosphates. These pollutants are removed using adsorbents via a process known as adsorption. Adsorbents used in the study are fish scales and neem leaves. Several studies have been carried out to measure the efficiency of adsorbents in the removal of contaminants. These studies include equilibrium studies, kinetic studies and isotherm studies. Based on a complete analysis and results obtained, 95% to 99% of contaminants can be removed effectively with an adsorbent dosage of 0.4g (0.2 g of fish scale and 0.2 g of neem leaves powder), optimum pH of 6 and at 303K constant temperature. The dosage variance stems from changing the dosages of two adsorbents in three ways, i.e., by taking both adsorbents in equal dosages, and increasing the dosage of one adsorbent compared to the other and vice versa. The contact time varied from 0 to 140min and the Initial concentration of pollutants has also been varied from 30 to 70 mg/L. In addition to the above variations, thermodynamic studies were also done, and based on the negative values of ΔG and positive value of ΔH and ΔS, it is evident that the reaction of novel adsorbent (combination of fish scales and neem leaves) is spontaneous and endothermic.

Application of the Fe3O4/ alginate/ diatomite nano-adsorbent for the adsorption of palladium and cyanide from wastewater: optimisation, kinetic and equilibrium studies

ABSTRACT In this research, the adsorption rates of cyanide and palladium onto Fe3O4/alginate/diatomite nano-adsorbent (FADA) were evaluated. The co-precipitation technique was applied to synthesis of FADA. The response surface methodology (RSM) was employed to investigate the relation between input-independent factors (initial pollutant concentration, contact time, FADA dosage and pH) and one dependent output response (removal efficiency). The best model was selected based on the results of the ANOVA analysis.SO model due to R2 of 0.929 and the insignificant lack of fit (0.12) for cyanide and also R2 of 0.98 and the insignificant lack of fit (0.12) for palladium was selected as an appropriate model for adsorption of both pollutants. Therefore, prediction and optimisation of the adsorption of the pollutants onto FADAwere done based on SO model. The best conditions for the adsorption of cyanide (95.65%) and palladium (92.66%) onto FADA were obtainedat (pH, 5.45; palladium concentration, 15.13 mg L−1; contact time, 104.8 min and FADA dosage, 0.98 g L−1) and (pH,7.0; cyanide concentration, 4.88 mg L−1; contact time, 91.06 min and FADA dosage, 2.05 g L−1), respectively. Investigation of the non-linear isotherm models indicated adsorptions of cyanide (R2 = 0.995) and palladium (R2 = 0.999) ontoFADA have reasonably fit to the Sips model.The maximum adsorption capacities of cyanide and palladium per mass unit of FADA were 208.55 mg g−1 and 60.2 mg g−1, respectively.The pseudo-first-order (R2 = 0.99) and the intra-particle diffusion (R2 = 0.96) were found to agreement well with the adsorption experimental data obtained for cyanide and palladium, respectively. Results indicated the sorption reactions of cyanide and palladium onto FADA were endothermic and exothermic, respectively.The present study indicated diatomite magnano composite boosted with alginate polymer beads due to high operating groups and also a high surface-to-volume ratio and porosity can be applied as an efficient adsorbent for the removal of cyanide and palladium from aqueous solutions.

بررسی اثر استفاده از زئولیت طبیعی کلینوپتیلولیت اصلاح شده در حذف نیترات، فسفات و شوری از زهاب کشاورزی در مدل زهکشی آزمایشگاهی

The feasibility of using zeolite clinoptilolite to filter nitrate and phosphate pollutants and salt from agricultural drainage-water was studied in the current research. Significant pollutant absorption parameters, such as adsorbent particle size, pollutant concentration, salinity, temperature, retention time, pH, and adsorbent concentration, were optimized in the batch condition. After the optimization of parameters, adsorption experiments were conducted on an experimental model, similar to subsurface drainage systems that are applied in farms. Adsorption experiments were carried out at optimized parameter levels on four models, namely a reference model (D0), a model with adsorbent around drains (D1), a model with adsorbent around plant roots (D2), and a model with adsorbent on the soil surface (D3); they were fed with untreated drainage-water from south Khuzestan farms during the fertilization season. The results were suggestive of a 63 percent Nitrate-removal efficiency, 39 percent Phosphate-removal efficiency and 79 percent salt-removal efficiency made possible by 30 g.L-1 of 1000 µm adsorbent particles, for a pH of 5, initial pollutant concentration of 80 mg.L-1 nitrate and 10 mg.L-1 phosphate, a 12 dS/m salinity, 90-minute retention time, and 50 °C ambient temperature. These parameter levels enabled nitrate, phosphate, and salt-removal efficiencies of 59.72 percent, 29.28 percent, and 77.47 percent respectively, in the model with clinoptilolite adsorbents around the drains (D1).

The Performance of Inorganic Salts/PMMA Nanocomposites in Ca and Mg Adsorption from Aqueous Solution

This study aimed to synthesize a new hybrid polymethyl methacrylate (PMMA) nanocomposites as catalysts in water treatment with high efficiency. We prepared three different materials, PMMA alone, then TiSO4/PMMA, and CaSO4/PMMA. After that, we made a screening experiment and found that TiSO4/PMMA was effective for Ca+2 removal and CaSO4/PMMA was effective for Mg+2 removal, and we made the optimization process according to this principle. The pH, contact time, dose, initial pollutant concentration, and temperature were performed to obtain the optimum parameters that achieve the highest Ca+2, Mg+2 removal efficiency as main cations causing hardness. The nanocomposite samples were characterized using different techniques. The CaSO4 nanoparticles were distributed uniformly across the CaSO4/PMMA matrix but TiSO4/PMMA has the parallel plate's morphology. Accordingly, the structures of the hybrids have been postulated. The maximum elimination value was 87.5% for Ca+2 and 65% for Mg+2. Adsorption isotherm and kinetics were demonstrated to set the nature of the reaction. Langmuir adsorption isotherm models were fitted with the experimental data for Mg+2 and Ca+2. The data of the pseudo-second-order kinetic model adequately fit the experimental values for the adsorption of Mg+2 and Ca+2. The positive values of ΔGo for Ca+2 (1.86 to 5.8 KJ/mol ) at all temperatures, and ΔGo for Mg+2 (1.5 KJ/mol) at 25oC indicated spontaneous adsorption process while the negative values for Mg+2 at 40oC and 60oC indicated a non-spontaneous adsorption process.

Pilot and Field Studies of Modular Bioretention Tree System with Talipariti tiliaceum and Engineered Soil Filter Media in the Tropics

Stormwater runoff management is challenging in a highly urbanised tropical environment due to the unique space constraints and tropical climate conditions. A modular bioretention tree (MBT) with a small footprint and a reduced on-site installation time was explored for application in a tropical environment. Tree species used in the pilot studies were Talipariti tiliaceum (TT1) and Sterculia macrophylla (TT2). Both of the MBTs could effectively remove total suspended solids (TSS), total phosphorus (TP), zinc, copper, cadmium, and lead with removal efficiencies of greater than 90%. Total nitrogen (TN) removal was noted to be significantly higher in the wet period compared to the dry period (p < 0.05). Variation in TN removal between TT1 and TT2 were attributed to the nitrogen uptake and the root formation of the trees species. A field study MBT using Talipariti tiliaceum had a very clean effluent quality, with average TSS, TP, and TN effluent EMC of 4.8 mg/L, 0.04 mg/L, and 0.27 mg/L, respectively. Key environmental factors were also investigated to study their impact on the performance of BMT. It was found that the initial pollutant concentration, the dissolved fraction of influent pollutants, and soil moisture affect the performance of the MBT. Based on the results from this study, the MBT demonstrates good capability in the improvement of stormwater runoff quality.

Au–SnO2–CdS ternary nanoheterojunction composite for enhanced visible light-induced photodegradation of imidacloprid

Herein, we have developed a novel synthetic strategy for the fabrication of Au–SnO2–CdS ternary nano-heterojunction catalyst and its utility towards LED light derived photocatalytic degradation of imidacloprid has been evaluated. The synthesized ternary nanocomposite was characterized using sophisticated analytical techniques to evaluate the catalyst's morphological, structural and surface chemical properties. The photocatalytic activity of the ternary catalyst towards the degradation of imidacloprid was evaluated under LED irradiation. Approximately 95% of the degradation efficiency was achieved with a pseudo-first-order reaction rate of 15.6 × 10−3 min−1. The degradation efficiency of Au–SnO2–CdS nano-catalyst was found to be ~1.2, 1.4 and 2.1 times to that of the pristine Au, CdS and SnO2 nanomaterials under similar experimental conditions. The effect of variation of parameters like contact time, initial pollutant concentration and pH on degradation efficiency has also been investigated. Moreover, the identification of various degradation products and reactive intermediates were made with high-performance liquid chromatography and electron spin resonance techniques.