Total Chromium Removal Research Articles

Large-scale removal of colloidal contaminants from artisanal wastewater by bipolar electrocoagulation with aluminum sacrificial electrodes

The large-scale removal of colloidal contaminants from artisanal activities was conducted through optimized bipolar electrocoagulation with lower energy consumption and aluminum sacrificial electrodes. As a result, over 90% simultaneous removal of total chromium, phosphorus, chemical oxygen demand and turbidity contents was achieved for relative short time (10–30 min), neutral pH of 7.0–7.5 and minimized current density. By optimization of the applied electrochemical parameters the elimination of carcinogenic colloidal chromium and organic mixture was modeled in a reproducible manner, and the reached purification levels of the effluents were acceptable for their reuse in the household. The practical usage of reported electrocoagulation design was successfully demonstrated as an effective alternative of the current conventional method for treatment of the tanning, domestic and artisanal industrial wastewater in Fez city, Morocco.

Nanoscale Zero Valent Iron Supported by Biomass-Activated Carbon for Highly Efficient Total Chromium Removal from Electroplating Wastewater

The application potential of nanoscale zero valent iron (nZVI) in wastewater treatment is huge and has attracted a lot of attention. In this study, the composite material BC-nZVI was prepared by emulsion of nZVI and biomass-activated carbon (BC) under the mechanical agitation condition, and was characterized by SEM-EDX, XRD, XPS, and FTIR. The decontamination abilities of BC-nZVI were tested by the removal of total chromium (Cr) from electroplating wastewater. The results showed that the removal efficiencies of Cr in the electroplating wastewater by nZVI particles can be effectively improved when supported with BC, but cannot be improved in its storage capacity. The chemical adsorption process between the Cr and BC-nZVI is the main rate-limiting step in the removal of total Cr from wastewater, and multiple parameters such as dosage, pH, and initial concentration of Cr was found to affect the rate.

Improved chromium reduction and removal from wastewater in continuous flow bioelectrochemical systems.

Bioelectrochemical systems (BESs) including microbial electrolysis cells (MECs) and microbial fuel cells (MFCs) are promising for hexavalent chromium [Cr(VI)] reduction and total chromium (Cr) removal from wastewater. This study assessed the performance of simple, inexpensive, and continuous flow BESs with neither cathode catalyst nor proton exchange membrane for Cr(VI) reduction and total Cr removal. The effect of bioreactor configuration and wastewater feed mode on the performance of the BESs was investigated. Biological Cr(VI) reduction in the MEC followed a first-order kinetics with a rate constant of 0.103 d-1, significantly higher than that of the control (0.033 d-1). For comparison, the first-order reduction rate constants in the MFCs with the Cr(VI) fed to the anodic and the cathodic zones were 0.072 and 0.064 d-1, respectively. The BESs improved total Cr removal through coprecipitating Cr(III) and phosphors as evidenced from the scanning electron microscopy energy-dispersive X-ray spectroscopy analysis. The total Cr removal efficiencies in the control, MFCs, and MEC were 26.1%, 56.7%, and 66.2%, respectively. Only 25.1% to 26.7% of total Cr was present intracellularly in the BESs (both MFCs and MEC), whereas 31.8% ± 1.4% and 38.0% ± 0.9% of total Cr in the anodic and cathodic zones of the control were present intracellularly. Overall, the BESs demonstrated a great potential to reduce Cr(VI) and removetotal Cr with the MEC having the fastest Cr(VI) reduction and most efficient total Cr removal. Furthermore, the BESs significantly reduced the intracellular total Cr content.

Removal of Hexavalent Chromium from Aqueous Solution by the Pod of Acacia gerrardii

Abstract This study aims at investigating the potential of Acacia gerrardii pod for the removal of Cr(VI) in batch system. Effect of solution pH, biosorbent dosage, initial concentration of Cr(VI), contact time on the removal process was examined. Complete removal of hexavalent chromium was achieved at pH values 1.0 and 2.0 whereas maximum removal of total chromium was obtained at pH of 3.0. The study showed that the biosorption and bioreduction mechanisms were involved in the removal process. The time required for complete removal of Cr(VI) using the pod of Acacia gerrardii was shortened with an increase in biomaterial dosage and decrease in Cr(VI) concentration. Kinetic data was well described using Park kinetic model. Freundlich isotherm model adequately fitted the equilibrium data indication multilayer adsorption of total chromium on the surface of biomaterial. The pod of Acacia gerrardii could be used efficiently for the removal of hexavalent chromium from aqueous solutions.

Total chromium removal from electroplating wastewater using Artocarpus Altilis leaves as adsorbent with continuous flow

Limbah cair elektroplating yang mengandung kromium (Cr) merupakan limbah yang berbahaya terhadap lingkungan. Limbah tersebut harus diolah terlebih dahulu sebelum dibuang ke lingkungan. Salah satu jenis pengolahan limbah cair yang mengandung Cr adalah proses adsorpsi. Batang dan daun Artocarpus altilis (daun sukun) mempunyai potensi untuk digunakan sebagai adsorben untuk mengolah limbah cair yang mengandung Cr. Proses aktivasi pada pembuatan adsorben dapat dilakukan secara asam ataupun non asam. Tujuan dari penelitian ini untuk mengetahui potensi daun sukun untuk mengadsopsi total Cr yang terkandung dalam limbah cair electroplating. Penelitian ini dilakukan menggunakan reactor dari pipa berukuran panjang 12 cm dan diameter 1,3 cm dengan aliran keatas secara kontinyu. Debit aliran yang digunakan pada penelitian ini sebesar 0,255 cm3/det. Total Cr diukur menggunakan Atomic Absorption Spectrophotometer (AAS). Hasil penelitian menunjukkan bahwa adsorpsi menggunakan yang dihasilkan dengan proses asam dapat mereduksi total-Cr dari 77,45 mg/l menjadi 0,474 mg/l (99,34) %, sedang adsorpsi menggunakan adsorben yang dihasilkan dengan proses non asam hanya menurunkan total-Cr dari 77,45 mg/l hingga mencapai 4,753 mg/l (93,86 %). Adsorpsi menggunakan adsorben daun Sukun yang diproduksi melalui proses asam dapat digunakan untuk mengolah limbah cair electroplating yang mengandung Cr sebab konsentrasi limbah terolah lebih rendah 0,5 mg/l ( sesuai Peraturan Menteri Lingkungan Hidup No.5, 2014)

Nano-pyrite as a Reductant to Remove Chromium in Groundwater

Removal of total chromium (CrT) by nano-pyrite (nano-FeS2) was investigated under different environmental conditions. Size of nano-FeS2 was in the range of 50−100 nm and it contained Fe and S. Removal kinetic rate constant of CrT was significantly dependent on the suspension pH and concentrations of CrT, nano-FeS2 and Humic Acid (HA). The removal kinetic rate constant of CrT by nano-FeS2 was decreased as the concentration of CrT was increased (0.43−0.29 min−1), while contradict kinetic result was observed as the concentration of nano-FeS2 was increased (1.11−2.78 min−1). The removal kinetic rate constant of CrT was significantly increased as the suspension pH increased (0.86−3.0 min−1). However, the removal kinetic rate constant of CrT was significant decreased in the present of HA (1.25−0.25 min−1). The removal kinetic rate constant of CrT by nano-FeS2 was strongly controlled by the reactive surface area of nano-FeS2. Identification of the formation of FeCr2O4 on the surface of nano-FeS2 reveals that adsorption, complexation and reduction reactions may occur during the removal reaction. This study provides fundamental knowledge on the fate of Cr under different groundwater conditions. Findings from this study can be used to enhance remediation technology of removal heavy metals from groundwater.

A co-operative endeavor by nitrifying bacteria Nitrosomonas and Zirconium based metal organic framework to remove hexavalent chromium

The problems associated with heavy metal pollution require effective methods for their decontamination. Biosorption is an eco-friendly option to alleviate this problem. In this work, we propose the utility of Nitrosomonas modified Zirconium metal organic framework as a novel biosorbent for the remediation of toxic hexavalent chromium. Detailed analytical characterization of the synthesized biosorbent was performed using various techniques such as Powder X-ray Diffraction (PXRD), Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermo Gravimetric analysis (TGA), Optical microscopy, Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), surface area and porosity measurements. The developed biosorbent has a surface area of 921 m2 g−1. Important batch adsorption parameters such as pH variation, adsorbent dosage, kinetics, isotherms and temperature variation were studied. A multilayer Freundlich adsorption and pseudo second order kinetics drive the exothermic biosorption process. The electrostatic interactions between the biosorbent surface and metal ions aid towards understanding the adsorption mechanism. Laboratory scale column studies were conducted and the regeneration of the biosorbent was done using sodium hydroxide. The validity of the method was tested in a certified reference material BCR-032 (Moroccan rock phosphate) for the removal of total chromium.

Magnetic hybrids synthesized from agroindustrial byproducts for highly efficient removal of total chromium from tannery effluent and catalytic reduction of 4-nitrophenol

The use of industrial waste to synthesize materials of technological interest is a rational way to minimize or solve environmental pollution problems. This work reports the removal of chromium ions from tannery effluent using magnetic hybrid adsorbents synthesized from waste biomass: coconut mesocarp (HCN), sugar cane bagasse (HBS), sawdust (HS), and termite nest (HT). The presence of organic matter and the cobalt ferrite phase in the structures of the materials were confirmed by XRD and FTIR analyses. Removal assays performed at different pH values showed the effectiveness of the adsorbents for removal at the natural pH of the effluent (pH 4.75), with adsorption capacity exceeding 6.6 mg g−1 for all the hybrids studied. The adsorption processes showed fast kinetics, with the HS hybrid removing 5.1 mg g−1 of the chromium species present in the effluent in the first 5 min. The HS hybrid presented the highest removal capacity, 6.7 mg g−1, while HBS showed the lowest, 6.6 mg g−1. The removal at equilibrium showed the following increasing order of efficiency of the hybrids: HBS < HCN < HT ≈ HS. The HCN and HT adsorbent matrices saturated with chromium ions (HCNCr and HTCr) showed excellent catalytic performance in the reduction of 4-nitrophenol, with 99.9% conversion within 180–240 s. The other hybrids did not present catalytic activity. The materials showed high capacities for reuse in two successive reduction cycles. The findings highlight the effectiveness of an industrial symbiosis approach to the development of new technologically important materials.

Development of a Functional Water Quality Index: a case study in Brahmani River Basin, India

The proposed study assesses the quality of water to find out the principal contributing factor responsible for the pollution in River Brahmani, India. These factors help the management and policymakers to set a marginal water quality standard. Physical, chemical, and biological parameters are taken for the study. Due to the notable dissimilarity in water quality parameters and spatiotemporal variability, significant objectives are proposed to assess the river water quality. The work presents a functional index which can be implemented for the comparative assessment of water quality across the River Basin controlled by several factors. The results showed that the quality of water could be improved by removal of total chromium for all the three seasons. The parameters such as sodium, potassium, lead, and nickel have positive effect and are considered to have high interference rate than that of other parameters such as chloride, cadmium, boron, sulfate, phosphate, fluoride, copper, zinc, nitrate, nitrite, and ammonia, which have negative effects on functional water quality index and are accounted as the parameters having low compliance rate. The water quality indexing methods done by previous authors are discussed extensively in the paper, which can provide an overall idea about indexing for further research.

Adsorption and Regeneration of Indonesian Natural Pumice for Total Chromium Removal from Aqueous Solution

To investigate the potential of adsorption and regeneration of natural pumice from West Sumatera Indonesia for total chromium (Cr) removal from aqueous solution, batch experiments in multiple adsorption-desorption cycles were performed. The results indicated that the optimum condition of total Cr removal were 3 of pH solution, 0.3 g/L of adsorbent dose, 60 min of contact time of adsorption, &lt;63 ?m of diameter of adsorbent, and 1 mg/L of total Cr initial concentration with 2.226 mg Cr/g pumice of total Cr uptake. The experimental data obtained were fitted with the Freundlich adsorption isotherm within the concentration range studied. Desorption efficiencies for total Cr ions by using 0.1 M HCl as desorbing agent were in the range of 31-32%. Although complete desorption were not attained, the natural pumice could be sufficiently reused up to 3 cycles of adsorption- desorption with increasing trend in total Cr uptake that may due to the surface modification of natural pumice caused by HCl. Overall results revealed that easy availability of natural pumice as local mineral in West Sumatra, Indonesia and its ability to adsorb and retain total Cr will create more interest to develop new natural adsorption method of pollutant removal from solution.

Improved removal of hexavalent chromium from 10 mg/L solution by new micron sized polymer clusters of aniline formaldehyde condensate

Removal of hexavalent chromium by aniline-formaldehyde condensate polymer coated on silica gel, in the past, showed poor removal at low concentration range with high adsorbent dose (∼30% removal at 10 mg/L with a adsorbent dose of 8 g/L). We have now synthesized a new form of the support less polymer which brings down residual concentration to less than 1 mg/L with a 2 g/L dose. The maximum removal of total chromium was observed between pH 3–8 (94–98% removal at 2 g/L dose). Removal is susceptible to processing of the polymer and batch to batch variation has been observed. Field emission scanning Electron microscope (FESEM) showed polymer consists of micron-sized (1–2 µm diameter) clusters. Phosphate and nitrate strongly inhibited total chromium uptake while effect of sulphate and chloride were less. Desorption was 86% with 1 N HCl and reuse of the micron sized AFC was possible for four cycles. Ion exchange as well as redox interaction between chromate ion and protonated amine group of polymer was found to be the key factor for adsorption.

Pilot‐Scale Removal of Total and Hexavalent Chromium From Groundwater Using Stannous Chloride

Alternative processes for hexavalent chromium (Cr(VI)) removal from drinking water continue to be of interest for utilities despite the existence of several established technologies. Stannous chloride (SnCl2) can reduce Cr(VI) to trivalent chromium, but research has been limited, especially related to the filterability of total chromium (Cr(T)) following reduction. At the pilot scale, SnCl2 was tested over a range of doses in three groundwaters with naturally occurring Cr(VI) concentrations ranging from 0.020 to 0.090 mg/L. Stannous chloride was found to be effective as a reductant at doses &lt;2 mg/L and contact times &lt;5 min. A tin‐to‐chromium molar dose ratio of 4 was sufficient for reducing Cr(VI) to below 0.010 mg/L. Cartridge filters were unable to practically remove Cr(T) following reduction, but a standard‐design sand filter was able to remove Cr(T) to &lt;0.010 mg/L.

Effect of pH on hexavalent and total chromium removal from aqueous solutions by avocado shell using batch and continuous systems.

Solution pH appears to be the most important regulator of the biosorptive removal of chromium ions from aqueous solutions. This work presents a kinetic study of the effects of solution pH on Cr(VI) and total chromium removal from aqueous solution by Hass avocado shell (HAS) in batch and continuous packed bed column systems. Different Cr(VI) and total chromium removal performances of HAS were obtained in pH-shift batch, pH-controlled batch, and continuous systems. These results emphasize the great importance of determining the most appropriate pH for Cr(VI) and total chromium removal, considering the operational mode of the proposed large-scale treatment system. Total chromium biosorption batch kinetics was well described by the Elovich model, whereas in the continuous system, the fitness of the kinetic models to the experimental data was pH dependent. X-ray photoelectron spectroscopy and kinetic studies clearly indicated that the reaction mechanism of Cr(VI) with HAS was the reductive biotransformation of Cr(VI) to Cr(III), which was partially released to the aqueous solution and partially biosorbed onto HAS.

Macadamia nutshells-derived activated carbon and attapulgite clay combination for synergistic removal of Cr(VI) and Cr(III)

A physical mixture of Macadamia-derived activated carbon and cationic attapulgite clay was investigated for total chromium removal in aqueous solution. The parameters influencing the adsorption of chromium on the sorbents were investigated, and it was shown that pH 3, contact time 2 hours, concentration 50 mg L−1 and calculated adsorption capacity of 96.28 mg g−1 were the optimal parameters. The process of adsorption was better described by Freundlich adsorption isotherm, and the kinetic modelling data suggested a chemisorption mechanism described by pseudo-second-order (PSO) rate model. Ionic strength studies demonstrated that the removal of anionic Cr(VI) species was mostly affected by the presence of anions like Cl− and [Formula: see text], while the removal of the cationic Cr(III) species was affected largely by cations [Formula: see text]&gt;Na+&gt;K+. Overall, the removal mechanism involved adsorption, reduction and ion exchange processes.

Combined energy and removal efficiency of electrochemical wastewater treatment for leather industry

Wastewater treatment and low energy consumption are two important environmental issues. In this work, a challenging treatment problem of leather industry wastewater is chosen as a case study to combine the issue of energy and treatment efficiency using a common denominator of oxygen demand. Tannery wastewater is known for its highly contaminated structure. Due to the acidic nature of the effluent, conventional methods do not perform well for tannery wastes, so an electrochemical process is a reasonable approach for the problem. Since electrochemical reactors use electricity, the energy efficiency of such plants should be simultaneously considered for overall sustainability. The electricity production partially results in carbon footprints and consumption of oxygen. In this work, the electrochemical treatment results were assessed through total chromium removal and chemical oxygen demand (COD) reduction. As expected, the electrochemical process parameters (reactor types, electrode variations, electrical current density, etc.) as well as the process duration affect the treatment performance. Meanwhile, these parameters also affect energy consumption. Although the energy consumption has been previously researched, (i) “the oxygen equivalent of the required energy” and (ii) “oxygen demand reduction of the wastewater” were not considered simultaneously before. In this work, the used energy is represented in terms of consumed oxygen at the current electric generation profile (in Turkey and in USA). It is argued that, as the consumed energy increases, the consumed oxygen also increases, causing a separate pollution (in terms of COD and other indirect effects). The combined production/consumption profiles as well as energy efficient parameter settings are investigated by experiments. It is observed that the combined oxygen demand (i.e. reduced on the treatment side and increased at the power generation side) starts exhibiting an overall increase at early treatment stages. For example, at an electrical current setting of 20 mA/cm2 and pH of 7, using electro-coagulation with aluminum electrodes, treatment reaches to 82% COD removal (from 1024 mg/L to 180.71 mg/L) at 8.33 kWh/m3, corresponding to consuming 3.23 g/L oxygen at average energy production settings in Turkey. The oxygen consumption using electro-Fenton exhibits similar results. The necessity of renewable energy utilization or an earlier treatment termination is concluded.

Influence of Magnetic Field Frequency Generated by Permanent Magnets in Mixed Culture Used for the Treatment of Effluent Contaminated with Chromium

This study focused on the treatment of effluent contaminated with chromium, being driven by the application of magnetic field studies in living cells and organisms. The objective was to quantify the removal of chromium(VI), total chromium, and total organic carbon (TOC) by applying a magnetic field generated by permanent magnets of neodymium in mixed culture. The resistance of microorganisms was evaluated for 4 h and 17 min against the application of a magnetic field at frequencies of 3, 5, and 10 Hz, which correspond to flow rates of 3.93, 7.07, and 14.92 cm3 s−1 in the system loop, respectively. The initial concentration of Cr(VI) was 100 mg L−1. The magnetic field frequency of 5 Hz showed a higher removal of Cr(VI) (100 %), total chromium (82 %), and TOC (34 %) compared with frequencies of 3 and 10 Hz and the absence of magnetic field exposure.

A COMPARATIVE STUDY ON RECOVERY OF CHROMIUM FROM TANNERY WASTEWATER AS NANO MAGNESIUM CHROMITE

In this paper, two different precipitation routes involving NaOH and MgO were investigated to remove chromium from tannery wastewater. It was found that the optimum pH for precipitation of chromium using NaOH or MgO was from 8.0 to 8.5 to give total chromium removal of 99.1 and 99.7%, respectively. The MgO route showed less sludge and shorter settling time (3h) compared with NaOH route. Furthermore, MgO enhanced dewatering of the sludge and the total chromium removal. Consequently, the chromium in the formed sludge was recovered as magnesium chromite (MgCr2O4) by calcination of the sludge in the temperature range of 550-650 ° C for 6 h. The formed magnesium chromite was characterized with the help of XRD, FE-SEM, FT-IR, TEM and thermal analyses (TGA and DSC). XRD analysis revealed the formation of cubic nano crystalline magnesium chromite powder at a temperature of 550-650 ° C for 6 h. TEM images show that the obtained powders exhibited nanospheres with particle a size less than 40 nm. Such formed materials were a good candidate in various applications such as refractory material and catalytic support.

Ailanthus Altissima and Phragmites Australis for chromium removal from a contaminated soil.

The comparative effectiveness for hexavalent chromium removal from irrigation water, using two selected plant species (Phragmites australis and Ailanthus altissima) planted in soil contaminated with hexavalent chromium, has been studied in the present work. Total chromium removal from water was ranging from 55% (Phragmites) to 61% (Ailanthus). After 360days, the contaminated soil dropped from 70 (initial) to 36 and 41mg Cr/kg (dry soil), for Phragmites and Ailanthus, respectively. Phragmites accumulated the highest amount of chromium in the roots (1910mg Cr/kg(dry tissue)), compared with 358mg Cr/kg(dry tissue) for Ailanthus roots. Most of chromium was found in trivalent form in all plant tissues. Ailanthus had the lowest affinity for Cr(VI) reduction in the root tissues. Phragmites indicated the highest chromium translocation potential, from roots to stems. Both plant species showed good potentialities to be used in phytoremediation installations for chromium removal.

Chromium Removal From Strong Base Anion Exchange Waste Brines

Regeneration of strong base anion (SBA) exchange resin produces concentrated and hazardous brine. In this research, one alternative regenerant and two brine treatment options were investigated to reduce the hazardous characteristics of the brine. These options included replacing sodium chloride with sodium bicarbonate as the regenerant, using ferrous sulfate (FeSO4) to reduce/coagulate hexavalent chromium (CrVI) in the brine, and applying weak base anion (WBA) exchange resin and chemical reductive media (CRM) to adsorb/reduce CrVI. It was found that bicarbonate was as effective as chloride in regenerating chromium‐saturated resins, and the affinity of the bicarbonate‐form resin for chromium was similar to that of the chloride‐form resin. It was observed that FeSO4 applied at doses close to the stoichiometric ratio achieved almost complete removal of total chromium from the SBA brine. In column tests, two CRM exhibited more than 20 times greater removal capacity for total chromium than did the WBA exchange resins.

Use of Box–Behnken design of experiments for the adsorption of chromium using immobilized macroalgae

Optimization experiments were carried using three-level Box–Behnken design for the adsorption of chromium onto immobilized macroalgae. The influence of independent parameters such as pH (2−8), temperature (303−333 K), and initial chromium concentration (20−100 mg/L) towards chromium ions removal has been performed. Second-order polynomial models were developed for the responses. The significance of the independent parameters and their interactions were investigated using the analysis of variance. The three-dimensional (3-D) response surface plots were used to study the interactive effects of the independent parameters on the chromium removal efficiency. The maximum Cr(VI) removal efficiency of 90.52, 90.86 was observed for Enteromorpha sp. immobilized in sodium alginate (ESA), Enteromorpha sp. immobilized in polysulfone (EPS), and maximum observed total chromium removal efficiency of 81.14, 79.90 was obtained for ESA, EPS, respectively. The observed value was in good agreement with the predicted values. These results indicated that immobilized macroalgae could be used for the removal of chromium from aqueous solution.