Maximum Metal Removal Research Articles

A comparative study for the removal of hexavalent chromium from aqueous solution by agriculture wastes’ carbons

This paper reports the feasibility of using agricultural waste and timber industry waste carbons to remove Cr(VI) from synthetic wastewater under different experimental conditions. For this, rice husk and saw dust have been used as adsorbent after sulphuric acid treatment. Effect of various process parameters, namely, pH, adsorbent dose, initial chromium concentration and contact time has been studied in batch systems. Maximum metal removal was observed at pH 2.0. The efficiencies of rice husk carbon (RHC) and saw dust carbon (SDC) for Cr(VI) removal were 91.75% and 94.33%, respectively for aqueous solutions (250 mg L(-1)) at 20 g L(-1) adsorbent dose. The experimental data was analyzed using Freundlich, Langmuir, Dubinin-Redushkevich (D-R) and Temkin isotherm models. It was found that Langmuir, D-R and Temkin models fitted well. The results revealed that the hexavalent chromium is considerably adsorbed on RHC and SDC and it could be an economical method for the removal of hexavalent chromium from aqueous systems. FTIR and SEM of the adsorbents were recorded in native and Cr(VI)-loaded state to explore the number and position of various functional groups available for Cr(VI) binding onto studied adsorbents and changes in adsorbent surface morphology. The surface area of RHC and SDC was 1.12 and 1.16 m(2)g(-1), respectively.

Effect of salinity on vanadate biosorption by Halomonas sp. GT-83: Preliminary investigation on biosorption by micro-PIXE technique

Thirty-eight soil samples were collected from crude oil contaminated land in south of Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum adsorption capacity of 52.7 mg vanadate/g dry weight. It was tentatively identified as Halomonas sp. according to morphological and biochemical properties and named strain GT-83. Removal of vanadate by biosorption with Halomonas sp. GT-83 was very sensitive to solution pH. Vanadate adsorption decreased with increasing pH, with maximum adsorption capacities achieved in at pH 3.0 in the absence and in the presence of increasing concentrations of salt. Vanadate-salt biosorption studies were also performed at this pH value. Equilibrium uptakes of vanadate increased with increasing vanadate concentration up to 600 mg/l. Maximum metal removal (91.8%) took place at pH 3.0 with initial vanadate concentration of 100 mg/l, which got reduced (84.8%) in the presence of 50 g/l salt. The equilibrium sorption data were analyzed by using Freundlich isotherm. The specific uptake of vanadate increased at low cell concentration and decreased when cell concentration exceeded 0.75 g/l. The paper also demonstrates the potential value of micro-PIXE in biosorption studies.

Removal of Cu(II) and Ni(II) from Industrial Effluents by Brown Seaweed, Cystoseira indica

The biomass of Cystoseira indica (RB) was chemically modified by cross-linking it with epichlorohydrin (CB1, CB2), and the same was oxidized by potassium permanganate (CB3) which was later employed for the treatment of Cu(II) and Ni(II) from effluents. The results indicated that biosorption equilibriums were rapidly established in about 30 and 75 min for Cu(II) and Ni(II), respectively. The metal biosorption was strictly pH dependent, and maximum removal of metals was observed at pH 6.0. The biosorption data dovetail the Langmuir isotherm, and the process obeyed pseudo-second-order kinetics. An intraparticle diffusion based Weber−Morris model was applied to evaluate rate-limiting steps, and the results suggested that film diffusion controlled the overall biosorption process. Fourier transform infrared analysis revealed that amino, hydroxyl, carboxyl, ether, and hydroxyl functional groups were involved in the metal binding and the sorption process was dominated by complexation as well as ion exchange. The ...

EXPERIMENTAL INVESTIGATIONS INTO THE INFLUENCING PARAMETERS OF ELECTROCHEMICAL MACHINING OF AISI 202

Electrochemical machining (ECM) is a non-traditional process used mainly to cut hard or difficult to cut metals, where the application of a more traditional process is not convenient. Those difficult to cut metals demand high energy to form chips, which can result in thermal effects due to the high temperatures inherent to the process in the chip–tool interface. In traditional processes, the heat generated during the cut is dissipated to the tool, chip, workpiece and environment, affecting the surface integrity of the workpiece, mainly for those hard materials. In this work, experimental investigations have been made on the various influencing parameters involved in the Metal removal rate (MRR) and Surface roughness using ECM on AISI 202 steel. The major intervening parameters are studied and the relationship between the parameters has been determined to achieve maximum metal removal rate and minimum surface roughness by using NaNO 3-Aqua solution.

The use of low cost and environment friendly materials for the removal of heavy metals from aqueous solutions

The objective of this study was to evaluate the use of rice husk and Nile rose plant for their ability to remove Cr (III), Cu(II), Zn(II), Cd(II) and Pb(II) from their mixed aqueous solution. The effects of contact time, pH, initial metal concentration and amount of adsorbent on the adsorption process at room temperature 25 ± 2°C were studied. Batch adsorption studies showed that an equilibrium time of 90 min. was required for the adsorption of Cr (III), Cu(II), Zn(II), Cd (II) and Pb(II) on both investigated adsorbents. The maximum metal removal was found to be pH dependent . With an increase in the concentrations of these metals, their adsorption decreased on both of the adsorbents. The experimental data were best fitted to the Temkin isotherm model. Rice husk and Nile rose plant were found to be good metal adsorbents. A case study was also performed to examine the feasibility of using the investigated adsorbents for treating real electroplating wastewater.

Chromium(VI) removal from aqueous system using Helianthus annuus (sunflower) stem waste

The objective of this study was to investigate the Cr(VI) removal efficiency of sunflower waste from aqueous system under different process conditions. Two adsorbents were prepared by pre-treating the sunflower stem waste. One adsorbent was prepared by boiling it and second adsorbent was prepared by treating it with formaldehyde. Batch mode experiments were carried out as a function of solution pH, adsorbent dosage, Cr(VI) concentration and contact time. FT-IR spectra and SEMs of the adsorbents were recorded to explore the number and position of functional groups available for the binding of Cr(VI) ions and morphology of the studied adsorbents. The removal of chromium was dependent on the physico-chemical characteristics of the adsorbent, adsorbate concentration and other studied process parameters. Maximum metal removal was observed at pH 2.0. The efficiencies of boiled sunflower stem absorbent and formaldehyde-treated sunflower stem absorbent for the removal of Cr(VI) were 81.7 and 76.5%, respectively for dilute solutions at 4.0 g/L adsorbent dose. The applicability of Langmuir, Freundlich and Dubinin–Radushkevich isotherms was also tested. The results revealed that the hexavalent chromium is considerably adsorbed on sunflower stem and it could be an economical method for the removal of hexavalent chromium from aqueous systems.

Removal of Cr(VI) from aqueous solutions using pre-consumer processing agricultural waste: A case study of rice husk

This paper reports the feasibility of using pre-consumer processing agricultural waste to remove Cr(VI) from synthetic wastewater under different experimental conditions. For this, rice husk, has been used after pre-treatments (boiling and formaldehyde treatment). Effect of various process parameters, namely, pH, adsorbent dose, initial chromium concentration and contact time has been studied in batch systems. The removal of chromium was dependent on the physico-chemical characteristics of the adsorbent, adsorbate concentration and other studied process parameters. Maximum metal removal was observed at pH 2.0. The efficiencies of boiled and formaldehyde treated rice husk for Cr(VI) removal were 71.0% and 76.5% respectively for dilute solutions at 20 g l −1 adsorbent dose. The experimental data were analyzed using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherm models. It was found that Freundlich and D–R models fitted well. The results revealed that the hexavalent chromium is considerably adsorbed on rice husk and it could be an economical method for the removal of hexavalent chromium from aqueous systems. FTIR and SEM were recorded, before and after adsorption, to explore number and position of the functional groups available for Cr(VI) binding on to studied adsorbents and changes in adsorbent surface morphology.

Removal of cadmium (II) from aqueous solutions by adsorption on agricultural waste biomass

This paper reports the feasibility of using various agricultural residues viz. sugarcane bagasse (SCB), maize corncob (MCC) and Jatropha oil cake (JOC) for the removal of Cd(II) from aqueous solution under different experimental conditions. Effect of various process parameters, viz., initial metal ion concentration, pH, and adsorbent dose has been studied for the removal of cadmium. Batch experiments were carried out at various pH (2–7), adsorbent dose (250–2000 mg), Cd(II) concentration (5–500 mgl −1) for a contact time of 60 min. The maximum cadmium removal capacity was shown by JOC (99.5%). The applicability of Langmuir and Freundlich isotherm suggests the formation of monolayer of Cd(II) ions onto the outer surface of the adsorbents. Maximum metal removal was observed at pH 6.0 with a contact time of 60 min at stirring speed of 250 rpm with an adsorbent dose of 20 g l −1 of the test solution. The maximum adsorption of cadmium (II) metal ions was observed at pH 6 for all the adsorbents viz; 99.5%, 99% and 85% for JOC, MCC, and SCB, respectively. Order of Cd(II) removal by various biosorbents was JOC > MCC > SCB. JOC may be an alternative biosorbent for the removal of Cd(II) ions from the aqueous solution. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of Cd(II) ions on to studied adsorbents. These results can be helpful in designing a batch mode system for the removal of cadmium from dilute wastewaters.

The use of fly ash as a low cost, environmentally friendly alternative to activated carbon for the removal of heavy metals from aqueous solutions

The objective of this study was to compare fly ash and activated carbon for their ability to remove nickel [Ni(II)] and zinc [Zn(II)] from an aqueous solution. The effects of contact time, pH, initial metal concentration and amount of adsorbent on the adsorption process at 20 ± 2 °C were studied. Batch kinetic studies showed that an equilibrium time of 1 h was required for the adsorption of Ni(II) and Zn(II) on both adsorbents. The maximum metal removal was found to be dependent on solution pH (4.0 for Ni(II) and Zn(II)). With an increase in the concentrations of these metals, the adsorption of Ni(II) and Zn(II) decreased on both of the adsorbents. The effectiveness of fly ash as an adsorbent improved with increasing calcium (CaO) content. Adsorption data in the range of pH values (3.0–8.0) using Ni(II) concentration of 25 ± 2 mg/L and Zn(II) concentration of 30 ± 2 mg/L in solution were correlated using the linear forms of the Langmuir and Freundlich equations. The fly ash was found to be a metal adsorbent as effective as activated carbon.

Optimization of EDM machining parameters using DMLS electrode

PurposeThe purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes.Design/methodology/approachIn this paper the effects of discharge current, pulse‐on‐time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi‐based L9 orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance.FindingsExperimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using DMLS electrode. Excessive DMLS tool (electrode) wear was also reported, which limits the use of DMLS tool for EDM machining and it has been found out that porosity (which was about 20 per cent) was one of the primary cause.Research limitations/implicationsThis paper was focused on understanding the effects of important EDM parameters on three performance characteristics (TWR, MRR and surface roughness). While this study identifies that DMLS electrode wear rate is high and porosity could be one of the main cause, presently it does not cover the investigations on reducing the porosity level and its implications.Practical implicationsThe DMLS material had shown huge potential to be used as EDM electrode. The current investigation established a structured experimental approach to understand the effects of EDM parameters on multi response characteristics. The results derived from this study helps to focus future research on two aspects including enriching the copper content and reducing the porosity level, thereby the benefits of lead time reduction in EDM electrode making could be realized.Originality/valueThe previous research attempts were not focussed on optimising the EDM machining process using rapid tooling electrodes. With the best of author's knowledge none of the researchers have reported these aspects especially for DMLS electrodes. Application of grey relational analysis for performance evaluation of rapid tooling‐based EDM electrodes (DMLS electrodes) appear to be completely new.

Biosorption of Cr(VI) by native isolate of Lyngbya putealis (HH-15) in the presence of salts

Industrial wastewaters containing heavy metals along with high concentration of soluble salts pose a major environmental problem that needs to be remedied. The present study reports on biosorption of Cr(VI) by native isolate of Lyngbya putealis HH-15 in batch system under varying range of pH (2.0–10.0), initial metal ion concentration (10–100 mg/l) and salt concentration (0–0.2%). Maximum metal removal (94.8%) took place at pH 3.0 with initial Cr concentration of 50 mg/l, which got reduced (90.1%) in the presence of 0.2% salts. Adsorption equilibrium and kinetic behavior of Cr(VI) in solution was also examined. Both Langmuir and Freundlich models fitted well to explain the adsorption data ( R 2 = 0.90 and 0.87, respectively) at 0.2% salt concentration. Pseudo-second order kinetic model also fitted well to both the systems, viz. Cr(VI) and Cr(VI) + salt.

Entrapment of fungal hyphae in structural fibrous network of papaya wood to produce a unique biosorbent for the removal of heavy metals

A unique biosorbent was developed by entrapping fungal hyphae in structural fibrous network of papaya wood (SFNPW) and successfully used for the removal of Zn(II) from aqueous solution. The SFNPW-immobilized fungal biosorbent removed Zn(II) rapidly and efficiently with maximum metal removal capacity of 66.17 mg/g dry biomass at equilibrium, 41.93% higher than the amount of Zn(II) removed by free biomass (46.62 mg/g) under the identical conditions. Equilibrium was established in 1 h and biosorption was well defined by Langmuir isotherm model. SFNPW-immobilized fungal biosorbent was regenerated by washing with 50 mM HCl, with upto 99% recovery of the sorbed metal ions and the regenerated system was reused in five adsorption–desorption cycles without any significant loss in its biosorption capacity. The efficient metal removing ability of this unique biosorbent system, low cost of SFNPW and simplicity of the immobilization technique used to produce the SFNPW-immobilized fungal biosorbent system indicate the potential application of this biosorbent for the treatment of wastewaters containing heavy metals.

Removal of nickel from aqueous solutions by sawdust

The main parameters influencing Nickel (II) metal sorption on maple sawdust were: initial metal ion concentration, amount of adsorbent, and pH value of solution. The maximum percent metal removal was attained after about 1 h. The greatest increase in the rate of adsorption of metal ions on sawdust was observed for pH changes from 2 to 5. An empirical relationship has been obtained to predict the percentage Nickel (II) removal at any time for known values of sorbent and initial sorbate concentration. The experimental results provided evidence for chelation ion exchange as the major adsorption mechanisms for binding metal ions to the sawdust. The adsorbent can be effectively regenerated using 0.1 M strong acid and reused.

Carbonised jackfruit peel as an adsorbent for the removal of Cd(II) from aqueous solution

The fruit of the jack ( Artocarpus heterophyllus) is one of the popular fruits in India, where the total area under this fruit is about 13,460 ha. A significant amount of peel (approximately 2714–11,800 kg per tree per year) is discarded as agricultural waste, as apart from its use as a table fruit, it is popular in many culinary preparations. Treatment of jackfruit peel with sulphuric acid produced a carbonaceous product which was used to study its efficiency as an adsorbent for the removal of Cd(II) from aqueous solution. Batch experiments were performed as a function of process parameters; agitation time, initial metal concentration, adsorbent concentration and pH. Kinetic analyses made with Lagergren pseudo-first-order, Ritchie second-order and modified Ritchie second-order models showed better fits with modified Ritchie second-order model. The Langmuir–Freundlich (Sips equation) model best defined the experimental equilibrium data among the three isotherm models (Freundlich, Langmuir and Langmuir–Freundlich) tested. Taking a particular metal concentration, the optimum dose and pH required for the maximum metal removal was established. A complete recovery of the adsorbed metal ions from the spent adsorbent was achieved by using 0.01 M HCl.

Improving the two-step remediation process for CCA-treated wood: Part II. Evaluating bacterial nutrient sources

Remediation processes for recovery and reuse of chromated-copper-arsenate- (CCA) treated wood are not gaining wide acceptance because they are more expensive than landfill disposal. One reason is the high cost of the nutrient medium used to culture the metal-tolerant bacterium, Bacillus licheniformis, which removes 70–100% of the copper, chromium, and arsenic from CCA-treated southern yellow pine (CCA-SYP) in a two-step process involving oxalic acid extraction and bacterial culture. To reduce this cost, the nutrient concentration in the culture medium and the ratio of wood to nutrient medium were optimized. Maximum metal removal occurred when B. licheniformis was cultured in 1.0% nutrient medium and at a wood to nutrient medium ratio of 1:10. Also, malted barley, an abundant by-product of brewing, was evaluated as an alternative nutrient medium. Tests were done to determine absorption of metals by barley, and the results indicate that the barley acted as a biosorbent, removing heavy metals from the liquid culture after their release from CCA to SYP. For comparison, tests were also performed with no nutrient medium. Following bacterial remediation, 17% copper and 15% arsenic were removed from an aqueous slurry of CCA-SYP (no medium). When oxalic acid extraction preceded the aqueous bacterial culture, 21% copper, 54% chromium, and 63% arsenic were removed. The two-step process (oxalic acid extraction and bacterial culture with nutrient medium) appears to be an effective, yet costly, way to remove metals.

The investigation on the prediction of tool wear and the determination of optimum cutting conditions in machining 17-4PH stainless steel

The purpose of this paper is to develop a predictive model for the prediction of tool flank wear and an optimization model for the determination of optimum cutting conditions in machining 17-4PH stainless steel. The back-propagation neural network (BPN) was used to construct the predictive model. The genetic algorithm (GA) was used in the optimization model. The Taguchi method (TM) was used to find the optimum parameters for both models, respectively. Two steps of experiments have been carried out by machining 6mm length and 90mm length of the workpiece, respectively. The experimental scheme was arranged by using an orthogonal array of TM. It has been shown that the predictive model is capable of predicting the tool flank wear in an agreement behavior. The optimization model has also been proved that it is a convenient and efficient method to find the optimum cutting conditions associated with the maximum metal removal rate (MMRR) under different constraints. The constraint is the tool flank wear that can be determined from the predictive model. Furthermore, the systematic procedure to develop the models in this paper can be applied to the usage of the predictive or optimized problems in metal cutting.

Optimization of machining parameters of Wire-EDM based on Grey relational and statistical analyses

Grey relational analyses are applied to determine the optimal selection of machining parameters for the Wire Electrical Discharge Machining (Wire-EDM) process. The Grey theory can provide a solution for a system in which the model is unsure or the information is incomplete. Besides, it provides an efficient solution to the uncertainty, multi-input and discrete data problem. Based on Taguchi quality design concept, an L18 mixed-orthogonal array table was chosen for the experiments. With both Grey relational analysis and a statistical method, it is found that the table feedrate had a significant influence on the metal removal rate, whilst the gap width and surface roughness were mainly influenced by pulse-on time. Moreover, the optimal machining parameters' setting for maximum metal removal rate and minimum surface roughness (or a desired surface roughness or a desired gap width) could be obtained by this approach.

Comparative study of adsorption properties of Turkish fly ashes: I. The case of nickel(II), copper(II) and zinc(II)

The objective of this study was to compare two different Turkish fly ashes (Afsin-Elbistan and Seyitomer) for their ability to remove nickel [Ni(II)], copper [Cu(II)] and zinc [Zn(II)] from an aqueous solution. The effect of contact time, pH, initial metal concentration and fly ash origin on the adsorption process at 20±2 °C were studied. Batch kinetic studies showed that an equilibrium time of 2 h was required for the adsorption of Ni(II), Cu(II) and Zn(II) on both the fly ashes. The maximum metal removal was found to be dependent on solution pH (7.0–8.0 for Ni(II), 5.0–6.0 for Cu(II) and 6.0–7.0 for Zn(II)) for each type of fly ash. With an increase in the concentrations of these metals, the adsorption of Ni(II) and Zn(II) increased while the Cu(II) adsorption decreased on both the fly ashes. Adsorption densities for the metal ions were Zn(II)>Cu(II)>Ni(II) for both the fly ashes. The effectiveness of fly ash as an adsorbent improved with increasing calcium (CaO) content. Adsorption data in the range of pH values (3.0–8.0) using Ni(II) and Cu(II) concentrations of 25±2 mg/l and Zn(II) concentration of 30±2 mg/l in solution were correlated using the linear forms of the Langmuir and Freundlich equations. The adsorption data were better fitted to the Langmuir isotherm since the correlation coefficients for the Langmuir isotherm were higher than that for the Freundlich isotherm. The fly ash with high calcium content (Afsin-Elbistan) was found to be a metal adsorbent as effective as activated carbon and, therefore, there are good prospects for the adsorptions of these metals on fly ash with high calcium content in practical applications in Turkey.

Substrate characterisation for a subsurface reactive barrier to treat colliery spoil leachate

Subsurface permeable reactive barriers (PRB) have been used to successfully treat acidic mine drainage in Canada and offer great potential for doing the same in the United Kingdom. A PRB for the treatment of colliery spoil leachate from a site near Newcastle upon Tyne, UK, has been designed. The selection of the reactive media to be used is of paramount importance, with particular reference to permeability and reactivity. A number of reactive media mixtures containing varying proportions of cattle slurry screenings, green waste compost, calcite limestone chips and pea gravel were prepared and their respective permeabilities and reactivities were investigated. Media mixtures containing 50% 10 mm grade calcite limestone chips showed better alkalinity addition and metals removal than a blank containing 50% pea gravel. A media mixture containing 50% limestone chips and 50% green waste compost showed a 24 h period to achieve maximum addition of alkalinity and maximum removal of acidity and metals. Mixtures containing 25% green waste compost and 25% slurry screenings achieved maximum addition/removal in 4 h. The likely presence of iron sulphide in samples drawn from test vessels during both test runs indicates that bacterial sulphate reduction is occurring in this composite.

CHARACTERIZATION OF A Ca-ALGINATE BASED ION-EXCHANGE RESIN AND ITS APPLICATIONS IN LEAD, COPPER, AND ZINC REMOVAL

Characterization of a novel ca-alginate based ion-exchange resin and its application in metal removal were investigated. The metal removal percentages increased from almost 0 to nearly 100% for metal concentrations < 0.1 mmol/L at pH 1.2 to 4, and a plateau was established at pH > 4. The removal percentages were in the following order: Pb2+ > Cu2+ > Zn2+ at pH < 4. Lower initial concentrations and ionic strengths slightly enhanced the removal percentage. The maximum metal removal capacities (q max) were 2.01 and 2.04 mmol/g for lead and copper, respectively, which are much higher than activated carbons and other reported biosorbents. Competitive effects were important for zinc removal, but less significant for lead and copper uptake. Organic chemical leaching from the resin was negligible. The single- and multiple-species metal ions were removed completely within approximately 90 and 130 minutes, respectively. The lead removal became much faster when its concentration was decreased and in the absence of other metal ions. Presence of competitive metal ions significantly reduced the metal uptake rate. Removal process kinetics were controlled by the mass transfer, while the local equilibrium followed an ion-exchange relationship.