Effective Removal Capacity Research Articles

Removal of protein wastes by amidoximated polyacrylonitrile nanofiber membrane decorated with dye wastes in batch and flow modes

Amidoximated polyacrylonitrile nanofiber membranes (P-Oxime) were functionalized with a reactive green 19 (RG19, as a model dye waste), to remove lysozyme as a soluble microbial protein model. The P-Oxime-RG19 nanofiber membranes were applied to remove lysozyme in batch and flow modes. The most effective removal capacity of P-Oxime-RG19 nanofiber membranes for lysozyme in batch mode was 1126.37 mg/g. The performance of P-Oxime-RG19 nanofiber membranes for removal of lysozyme in flow mode was further investigated under different pH values, loading flow rates, and loading concentrations of lysozyme. The influences of process parameters on the shape of the breakthrough curve were analyzed, and the experimental results were fitted with various dynamic models to understand the removal behavior of P-Oxime-RG19 nanofiber membranes. The results illuminated the substantial variations in the dynamic binding characteristics of P-Oxime-RG19 nanofiber membranes, including breakthrough time, dynamic binding capacity, mass transfer zone length, and membrane bed utilization. The adsorbed lysozyme could be completely washed out from the dyed membrane using 1.5 M NaCl.

Removal performance and mechanism of tetracycline hydrochloride in aqueous by geopolymers from tourmaline tailings

Tetracycline hydrochloride (TCH) is one of the widespread pollutants in wastewater, which easily causes severe threat to human health and ecological environment. Geopolymers (GPs) have demonstrated potential applications as adsorbents for effluent treatment. Herein, a research on the removal performance and mechanism of TCH by geopolymers from tourmaline tailings (TMT) was introduced. The TMT exhibited the typical characteristics of the amorphous state of geopolymer gel to varying degrees under a series of alkali activator modulus, and the sample with a modulus of 1.2 had the highest average pore diameter and specific surface area, which were 5.83 nm and 150.17 m2·g−1, respectively. The kinetic data were well fitted by pseudo-second-order kinetic model for the adsorption process of TCH on TMT-GP1.2, and the maximum theoretical adsorption capacity, obtained from the Langmuir model, was 105.4 mg·g−1 at 318 K and pH= 5. Thermodynamics indicated that the adsorption process of TCH on TMT-GP1.2 was not only endothermic, but also feasible and spontaneous. The adsorption of TCH by TMT-GP1.2 involved the combined effect of physical and chemical adsorption, including pore filling, electrostatic attraction, hydrogen bonding and ion exchange interactions. Notably, TMT-GP1.2 might show the superposition of excellent functions from the geopolymers and schorl, especially in ion exchange and electrostatic attraction, thus enhancing the removal efficiency of TCH. The adsorption capacity of the TMT-GP1.2 for TCH reached 46.64 mg·g−1 after 5 cycles. Based on the price-effectiveness, effective removal capacity and acceptable reusability, the tourmaline tailings geopolymers were expected to be potential environmentally friendly TCH adsorbents.

Highly durable covalent organic framework for the simultaneous ultrasensitive detection and removal of noxious Hg2+

Designed porous materials, such as covalent organic frameworks (COFs), are promising materials for the removal of toxic metals from wastewater. To assess the contamination and removal of toxic metal ions, their ultrasensitive detection is extremely important. However, to date, there have been very few reports on the ultrasensitive (picomolar) detection of toxic metal ions using highly porous COFs. Therefore, in this study, we synthesized a highly porous and durable COF containing amine and sulfonyl groups using the hydrothermal method. We demonstrated the impressive performance of obtained COF for the selective and ultrasensitive detection of Hg2+. Owing to its excellent luminescence properties and highly p-conjugated system, this metal-free COF can be used as a signal transducer for the selective and sensitive detection of Hg2+ at the picomolar level (640 pM). We studied the influence of various factors (e.g., pH, concentration, and temperature) on the sensitive detection of Hg2+. Owing to excellent luminescence properties and ultrasensitive detection of Hg2+, COF works as highly adsorbent materials for Hg2+ with the effective removal capacity of 99.8% at neutral pH. The obtained COF was also applied as a probe for the simultaneous detection and removal of Hg2+ in a natural river water sample. The results indicate a new path toward metal-free chemical sensors for toxic pollutants.

Distribution and Removal of Polycyclic Aromatic Hydrocarbons and Their Derivatives in SBR/MBBR Process

While polycyclic aromatic hydrocarbons (PAHs) are an important persistent toxic organic contaminant, the toxicities of substituted polycyclic aromatic hydrocarbons (SPAHs) are much higher than PAHs. Water and sludge samples were collected from the Qingdao Chengyang Sewage Treatment Plant (STP). The distribution and removal of 16 PAHs and nitro-PAHs (NPAHs), methyl-PAHs (MPAHs), and oxy-PAHs (OPAHs) in the SBR/MBBR process were analyzed. The results showed that 16 PAHs and 13 SPAHs were detected. In the influent water, the total concentrations of PAHs and SPAHs were 3835.14 ng·L-1 and 6889.46 ng·L-1, respectively, which were much higher than those of STPs in other regions. In the effluent, the total concentrations of PAHs and SPAHs were 1148.18 ng·L-1 and 1724.57 ng·L-1, respectively, and the removal rates were up to 70.06% and 74.97%, respectively. The SBR/MBBR process presented a more effective removal capacity for PAHs and SPAHs. The removal of PAHs was mainly by the biodegradation of low-ring polycyclic aromatic hydrocarbons (LMW-PAHs)in the aqueous phase; while the removal of PAHsin the particle phase mainly relied on the adsorption and precipitation of LMW-PAHs in the primary sedimentation tank and the biosorption of high-ring polycyclic aromatic hydrocarbons (HMW-PAHs) in the bio-unit. For SPAHs, the removal efficiency of MPAHs (up to 89.15%) was the best under the functions ofparticle adsorption and biodegradation. The removal rate of OPAHs was 63.36%, which was mainly removed by the adsorption of primary particles in the aqueous phase and the biosorption from the biological treatment unit in the particlephase, and the removal rate of NPAHs was 48.85% and largely occurred in the biological treatment unit. The removal mechanism of SPAHs in SBR/MBBR process was not the same. Therefore, STPs should take adequate control measures according to the distribution characteristics of PAHs and SPAHs in different treatment units. Additionally, the concentrations of PAHs and SPAHs in sludge were higher than those in the effluent. Thus, the management of PAHs and SPAHs in sludge should be improved.

Removal of sulfur compounds from petroleum refinery wastewater through adsorption on modified activated carbon

The adsorption of sulfur compounds from petroleum refinery wastewater on a chemically modified activated carbon (MAC) was investigated. The modification technique (nitric acid, hydrogen peroxide and thermal modification) enhanced the removal capacity of carbon and therefore decreases cost-effective removal of sulfide from refinery wastewater. Adsorption equilibrium and kinetics data were determined for sulfur removal from real refinery wastewater. The data were evaluated according to several adsorption isotherm and kinetics models. The Freundlich isotherm fitted well with the equilibrium data of sulfur on different adsorbents, whereas the kinetics data were best fitted by the pseudo-second-order model. Insights of sulfide removal mechanisms indicated that the sorption was controlled through the intraparticle diffusion mechanism with a significant contribution of film diffusion. The MAC adsorbent was found to have an effective removal capacity of approximately 2.5 times that of non-modified carbon. Using different MAC, sulfides were eliminated with a removal capacity of 52 mg g(-1). Therefore, MAC can be utilized as an effective and less expensive adsorbent for the reduction of sulfur in refinery wastewater.

Ferrous iron removal by limestone and crushed concrete in dynamic flow columns

In-situ passive reactive barriers containing carbonate minerals show potential for dissolved iron removal from groundwater at landfill sites. The removal of Fe(II) from synthetic groundwater using limestone and crushed concrete (7–10 mm) was evaluated using dynamic flow columns. Solutions of 50 mg/L Fe(II) were passed through duplicate columns of limestone and concrete until breakthrough (250–300 days); water quality was evaluated at distinct column depths throughout the study. Each material was successful in reducing the concentration of Fe(II), with both achieving an average of greater than 99.4% iron removal (<0.3 mg/L effluent concentration) over 288 and 216 pore volumes, resulting in effective removal capacities of 4.06 and 3.80 g Fe/kg reactive material for limestone and crushed concrete, respectively. These values are less than removal capacities achieved from a sequencing batch test (32.9 and 27.9 g Fe/kg limestone and crushed concrete, respectively), a possible result of preferential flow pathways, shorter equilibration time, and formation of surface films on the reactive materials in the columns.

A Test of Three Macrophyte Species to Reduce Total Nitrogen and Total Phosphorus from Wastewater

Three aquatic macrophytes (Acorus calamus, Lythrum salicaria and Sagittaria sagittifolia) were grown in monoculture to test the relative growth rate(RGR) and abilities of removing total nitrogen(TN) and total phosphorus (TP) by the manipulative indoor experiment. A nutrient treatment consisted of four levels of nitrogen (N) and phosphorus (P) [low (14 mg L-1 N and 3 mg L-1 P) and high (56 mg L-1 N and 12 mg L-1 P)] of nutrient solution. Result revealed that the RGR of the species was significantly different, however nutrients had no significant affect on the RGR. Also the abilities of different macrophyte species to remove nitrogen and phosphorous contrast sharply with one another. The results showed that TN and TP in wastewater were significantly higher from unvegetated microcosms compared to vegetated. A. calamus was shown to be best removal effect with the removal rates of 96.4% and 71.5% at low and high concentrations of TN. Furthermore A. calamus was generally effective removal capacity of TP at low nutrient level, but the performance of L. salicaria at reducing phosphorus at high nutrient level was relatively high.

Application of Electrocoagulation Process Using Iron and Aluminum Electrodes for Fluoride Removal from Aqueous Environment

Fluoride in drinking water above permissible level is responsible for human being affected by skeletal fluorosis. The present study was carried out to assess the ability of electrocoagulation process with iron and aluminum electrodes in order to removal of fluoride from aqueous solutions. Several working parameters, such as fluoride concentration, pH, applied voltage and reaction time were studied to achieve a higher removal capacity. Variable concentrations (1, 5 and 10 mg L-1) of fluoride solutions were prepared by mixing proper amount of sodium fluoride with deionized water. The varying pH of the initial solution (3, 7 and 10) was also studied to measure their effects on the fluoride removal efficiency. Results obtained with synthetic solution revealed that the most effective removal capacities of fluoride could be achieved at 40 V electrical potential. In addition, the increase of electrical potential, in the range of 10‐40 V, enhanced the treatment rate. Also comparison of fluoride removal efficiency showed that removal efficiency is similar with iron and aluminum electrodes. Finally it can be concluded that the electrocoagulation process has the potential to be utilized for the cost‐effective removal of fluoride from water and wastewater.

Synthesis of mesoporous carbon capsules encapsulated with magnetite nanoparticles and their application in wastewater treatment

Mesoporous carbon capsules encapsulated with Fe3O4 nanoparticles were prepared by the successive coating of a silica layer and a subsequent mesoporous silica/carbon layer on the surface of Fe3O4 nanoparticles followed by chemical etching with NaOH solution. TEM observations show that the as-obtained samples had a rattle-like structure: Fe3O4 nanoparticles were encapsulated in the interior of the mesoporous carbon capsules. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1570 m2 g−1, and the total pore volume is about 3.02 cm3 g−1. The porous wall structure of the lateral carbon capsules provides the sufficient spaces that contribute to high adsorption capacities and faster adsorption rates of pollutants molecules in aqueous media. The nanocomposites are superparamagnetic at room temperature with a saturation magnetization of 5.5 emu g−1, which provides the prerequisite for the fast magnetic separation in wastewater treatment application. Water treatment experiments indicated that the as-prepared samples exhibited higher adsorption rates and more effective removal capacity of organic pollutants compared with commercial activated carbon (AC), and their maximum adsorption capabilities for methylene blue (MB), congo red (CR), and phenol reached 608.04, 1656.9 and 108.38 mg g−1, respectively. The multifunctional nanocomposites can be potentially used as absorbents for fast, convenient, and highly efficient removal of pollutants from the wastewater, which will play important roles in the purification or desalination of natural water and industrial effluents.

APPLICATION OF ELECTROCOAGULATION PROCESS IN REMOVAL OF ZINC AND COPPER FROM AQUEOUS SOLUTIONS BY ALUMINUM ELECTRODES

In this study, the performance of electro-coagulation in combination with aluminum sacrificial anode, in removal of zinc and copper has been investigated. Several parameters, such as pollutant concentration, pH, electrical potential, COD, turbidity and contact time were studied to achieve a higher removal capacity. Variable concentrations (5-50-500 ppm) of zinc and copper solu- tions were prepared. In order to follow the progress of the treatment, samples of 25mL were taken at 15 min intervals up to 60 min and then filtered with 0.45 ى diameter to eliminate sludge formed during electrolysis. The varying pH of the initial solution was also studied to measure their effects on the zinc and copper removal efficiency. Results obtained with synthetic wastewater revealed that the most effective removal capacities of studied metals could be achieved at 40 V electrical potential. In addition, the increase of electrical potential, in the range of 20-40 V, enhanced the treatment rate without affecting the charge loading required to reduce metal ion concentrations under the admis- sible legal levels. The process was successfully applied to the treatment of an electroplating waste- water where an effective reduction of zinc and copper concentration under legal limits was obtained, just after 15-60 min. Moreover, it can be concluded that the electro-coagulation process has the potential to be utilized for the cost-effective removal of heavy metals from water and wastewater.

Multifunctional biomagnetic capsules for easy removal of phenol and bisphenol A

This paper reports fabrication, optimization and characterization of multifunctional biocapsules with immobilized enzyme using a layer-by-layer configuration and their application for removal of phenol and bisphenol A (BPA). The method is based on the combined use of enzymatic oxidation of the BPA and subsequent binding of the reaction product onto a chitosan core biopolymer. This platform has multiple functions including: (1) enzymatic degradation of BPA, (2) adsorption of the degraded compound within the core material, (3) colorimetric quantification and (4) magnetic capabilities. We examined various configurations of core/shell structures of alginate and chitosan and determined the stability and the optimum conditions in which these structures provide the most effective removal capacity. The amount of BPA that can be removed per capsule is 5.6 ppm while phenol can be removed up to 10 ppm per capsule within 15 h.

Use of adsorption using granular activated carbon (GAC) for the enhancement of removal of chromium from synthetic wastewater by electrocoagulation

The present work deals with removal of hexavalent chromium from synthetic effluents in a batch stirred electrocoagulation cell with iron–aluminium electrode pair coupled with adsorption using granular activated carbon (GAC). Several working parameters such as pH, current density, adsorbent concentration and operating time were studied in an attempt to achieve higher removal capacity. Results obtained with synthetic wastewater revealed that most effective removal capacities of chromium (VI) could be achieved when the initial pH was near 8. The removal of chromium (VI) during electrocoagulation, is due to the combined effect of chemical precipitation, coprecipitation, sweep coagulation and adsorption. In addition, increasing current density in a range of 6.7–26.7 mA/cm 2 and operating time from 20 to 100 min enhanced the treatment rate to reduce metal ion concentration below admissible legal levels. The addition of GAC as adsorbent resulted in remarkable increase in the removal rate of chromium at lower current densities and operating time, than the conventional electrocoagulation process. The method was found to be highly efficient and relatively fast compared to existing conventional techniques.

Electrocoagulation of vegetable oil refinery wastewater using aluminum electrodes

Electrocoagulation with aluminum electrodes was used to treat the vegetable oil refinery wastewater (VORW) in a batch reactor. The effects of operating parameters such as pH, current density, PAC (poly aluminum chloride) dosage and Na 2SO 4 dosage on the removal of organics and COD removal efficiency have been investigated. It has been shown that the removal efficiency of COD increased with the increasing applied current density and increasing PAC and Na 2SO 4 dosage and the most effective removal capacity was achieved at the pH 7. The results indicate that electrocoagulation is very efficient and able to achieve 98.9% COD removal in 90 min at 35 mA cm −2 with a specific electrical energy consumption of 42 kWh (kg COD removed) −1. The effluent was very clear and its quality exceeded the direct discharge standard.

Treatment of electroplating wastewater containing Cu 2+, Zn 2+ and Cr(VI) by electrocoagulation

The performance of electrocoagulation, with aluminium sacrificial anode, in the treatment of metal ions (Cu 2+, Zn 2+ and Cr(VI)) containing wastewater, has been investigated. Several working parameters, such as pH, current density and metal ion concentrations were studied in an attempt to achieve a higher removal capacity. Results obtained with synthetic wastewater revealed that the most effective removal capacities of studied metals could be achieved when the pH was kept between 4 and 8. In addition, the increase of current density, in the range 0.8–4.8 A dm −2, enhanced the treatment rate without affecting the charge loading, required to reduce metal ion concentrations under the admissible legal levels. The removal rates of copper and zinc were found to be five times quicker than chromium because of a difference in the removal mechanisms. The process was successfully applied to the treatment of an electroplating wastewater where an effective reduction of (Cu 2+, Zn 2+ and Cr(VI)) concentrations under legal limits was obtained, just after 20 min. The electrode and electricity consumptions were found to be 1 g l −1 and 32 A h l −1, respectively. The method was found to be highly efficient and relatively fast compared to conventional existing techniques.

Modified activated carbon for the removal of copper, zinc, chromium and cyanide from wastewater

Modified activated carbon are carbonaceous adsorbents which have tetrabutyl ammonium iodide (TBAI) and sodium diethyl dithiocarbamate (SDDC) immobilised at their surface. This study investigates the adsorption of toxic ions, copper, zinc, chromium and cyanide on these adsorbents that have undergone surface modification with tetrabutyl ammonium (TBA) and SDDC in wastewater applications. The modification technique enhance the removal capacity of carbon and therefore decreases cost-effective removal of Cu(II), Zn(II), Cr(VI) and CN− from metal finishing (electroplating unit) wastewater. Two separate fixed bed modified activated carbon columns were used; TBA-carbon column for cyanide removal and SDDC-carbon column for multi-species metal ions (Cu, Zn, Cr) removal. Wastewater from electroplating unit containing 37 mg l−1 Cu, 27 mg l−1 Zn, 9.5 mg l−1 Cr and 40 mg l−1 CN− was treated through the modified columns. A total CN− removal was achieved when using the TBA-carbon column with a removal capacity of 29.2 mg g−1 carbon. The TBA-carbon adsorbent was found to have an effective removal capacity of approximately five times that of plain carbon. Using SDDC-carbon column, Cu, Zn and Cr metal ions were eliminated with a removal capacity of 38, 9.9 and 6.84 mg g−1, respectively. The SDDC-carbon column has an effective removal capacity for Cu (four times), Zn (four times) and Cr (two times) greater than plain carbon.