Hydroxide Precipitation Method Research Articles

Inducing Magnetic Properties with Ferrite Nanoparticles in Resins for Additive Manufacturing.

Additive manufacturing and nanotechnology have been used as fundamental tools for the production of nanostructured parts with magnetic properties, expanding the range of applications in additive processes through tank photopolymerization. Magnetic cobalt ferrite (CoFe2O4) and barium ferrite (BaFe12O19) nanoparticles (NPs) with an average size distribution value (DTEM) of 12 ± 2.95 nm and 37 ± 12.78 nm, respectively, were generated by the hydroxide precipitation method. The dispersion of the NPs in commercial resins (Anycubic Green and IRIX White resin) was achieved through mechanochemical reactions carried out in an agate mortar for 20 min at room temperature, with limited exposure to light. The resulting product of each reaction was placed in amber vials and stored in a box to avoid light exposure. The photopolymerization process was carried out only at low concentrations (% w/w NPs/resin) since high concentrations did not result in the formation of pieces, due to the high refractive index of ferrites. The Raman spectroscopy of the final pieces showed the presence of magnetic NPs without any apparent chemical changes. The electron paramagnetic resonance (EPR) results of the pieces demonstrated that their magnetic properties were maintained and not altered during the photopolymerization. Although significant differences were observed in the dispersion process of the NPs in each piece, we determined that the photopolymerization did not affect the structure and superparamagnetic behavior of ferrite NPs during processing, successfully transferring the magnetic properties to the final 3D-printed piece.

Metal sulfide precipitation mediated by an elemental sulfur-reducing thermoacidophilic microbial culture from a full-scale anaerobic reactor

Biological sulfidogenic systems are advantageous over hydroxide precipitation methods to recover base metals from hot and acidic metallurgical streams. Sulfide precipitation is not widely used in the hydrometallurgical industry for the high operational and capital expenses associated with compartmentalizing the sulfidogenic and metal precipitation process. A single-stage elemental sulfur-reducing process in which sulfidogenesis and metal precipitation occur concurrently could significantly decrease these costs. This study examines the effect of metals on the sulfidogenic activity of an adapted thermoacidophilic sulfur-reducing culture. Batch tests were conducted with Cu2+, Ni2+, and Zn2+ in concentrations up to 100, 570, and 525 mg L−1, respectively. All metal ions were completely precipitated (LOQ < 0.1 mg L−1) with higher volumetric sulfide production rates than in the experiments without metals. Dissolved metals appear to stimulate the sulfur reduction metabolism in a redox-dependent process. Additionally, we investigated the use of an unadapted microbial inoculum from a full-scale anaerobic reactor as a fast start-up inoculum for a sulfidogenic process under high temperature (80 °C), low pH (pH 3), and high Cu2+ concentrations (up to 1143 mg L−1). After seven days of operation, we found equivalent sulfidogenic rates to those obtained after 75 days of adaptation with the same inoculum. These results encourage the development of a single-stage metal precipitation and sulfur-reducing process under conditions suitable for thermoacidophilic microorganisms.

Wastewater Treatment in Mineral Processing of Non-Ferrous Metal Resources: A Review

Water used by mining enterprises needs to be comprehensively recovered and utilized to achieve clean production. This requires the effective treatment of mineral processing wastewater. Wastewater produced during non-ferrous metal mineral processing contains a complex mixture of pollutants at high concentrations, making comprehensive treatment difficult. Here, the sources of and hazards posed by wastewater produced during non-ferrous metal mineral processing are introduced and the techniques for removing heavy metal ions and organic chemicals are reviewed. Chemical precipitation and adsorption methods are often used to remove heavy metal ions. Chemical precipitation methods can be divided into hydroxide and sulfide precipitation methods. Organic chemicals are mainly removed using oxidation methods, including electrochemical oxidation, photocatalytic oxidation, and ultrasonic synergistic oxidation. External and internal cyclic utilization methods for treating wastewater produced by mineral processing plants are introduced, and a feasibility analysis is performed.

Effect of Surfactant Type on Synthesis and Characteristics of Nanonickel Hydroxide

Nickel hydroxide has a vital role in various applications, especially as a support material for energy storage materials. Nickel hydroxide can be synthesized through the hydroxide precipitation method. However, the product formed by this method may be large or more than 100 nm because the agglomeration step can occur easily. This present work aims to study the effect of surfactant types in the synthesis and characterization of nickel hydroxide nanoparticle. Nickel sulfate (NiSO4) solution was used as a precursor solution, while 5M sodium hydroxide (NaOH) solution was used as a precipitation agent. The surfactants studied were alkyl benzene sulfonate (ABS), sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP). The nickel hydroxide synthesis process was carried out at 50 oC for 1 hour. The surfactant concentration used was at the critical micelle concentration (CMC), where the CMC for ABS, SDS, CTAB, and PVP were 0.01; 0.05; 3; and 0.5 %w/v, respectively. The synthesis of nickel hydroxide nanoparticle was carried out successfully precipitated almost 100% of Ni2+ ions. The product characterization that has been carried out shows that ABS surfactant produces the best nickel hydroxide nanoparticle product where the particle size is 3.12–4.47 nm.

Extracting lithium from the H2SO4 leaching solution of bauxitic claystone via co-precipitation methods without addition of Al source

Newly mined bauxitic claystone resources have received attention due to the rapidly growing demand for lithium. However, existing methods for extracting lithium from bauxitic claystone are still difficult and costly. This study proposed a novel aluminum hydroxide precipitation method to improve the extraction rate of Li by cleverly utilizing Al from bauxitic claystone. First, the ball-milled and calcined bauxitic claystone samples were leached by sulfuric acid to obtain a leaching solution with a high concentration of Al3+. Then, a NaOH solution was added to form amorphous aluminum hydroxide to adsorb Li+. The precipitation rate of Li+ reached 97.2% under the suitable precipitation conditions. Lastly, the precipitate was calcined and leached with deionized water to extract lithium. Li+ reached a water-leaching rate of 86.13%. According to the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results, the prepared precipitate was mainly amorphous aluminum hydroxide and part was composed of a gibbsite phase. The elution experiment showed that the amorphous aluminum hydroxide had good adsorption selectivity for Li+. In addition, Al2O3 could be recovered from the solid phase after water-leaching, which can significantly reduce the cost.

SYNTHESIS AND CHARACTERIZATION OF NICKEL HYDROXIDE FROM EXTRACTION SOLUTION OF SPENT CATALYST

Nickel is an essential metal element and is applied in various sectors. One of the useful nickel–based derivatives products is nickel hydroxide [Ni(OH)2]. This compound is widely applied as raw material for electrodes of rechargeable batteries, capacitors, electrolyzers, and catalysts. This study focuses on the synthesis of Ni(OH)2 using the hydroxide precipitation method. A solution from the extraction process of spent catalysts was used as a precursor solution. After the precursor solution was obtained, the precipitation process was carried out at pH 10, where the operating temperature was varied at 30–60oC. NaOH, KOH, and MgO solutions were used as precipitating agents. The experimental results show that the Ni(OH)2 compounds were produced optimally at low temperatures, 30oC. It could be indicated from the lowest concentration of Ni2+ ions in the liquid phase that reached that temperature. The three precipitation agents also gave good results in the precipitation of Ni2+ ions, where almost all of the Ni2+ ions were precipitated from the liquid phase. The precipitated products were characterized using SEM, XRD, and XRF. The analysis results showed that the product was agglomerated and formless. The purity of the precipitates formed were 24.1 and 29% for the precipitating agents MgO and NaOH, respectively.

Zinc Removal from ZnO Industrial Wastewater by Hydroxide Precipitation and Coagulation Methods: The Role of pH and Coagulant Dose

Liquid waste from the ZnO industry must be treated to meet the quality standards of wastewater into water bodies, according to the Minister of Environment Regulations No.5, 2014. It still contains 79 mg/L of Zn metal, cloudy with turbidity above 500 NTU, and COD value around 222 mg/L. This study aims to determine the effect of pH on reducing Zn metal and the coagulant dose to minimize turbidity and COD in liquid waste produced by the ZnO factory in Depok, West Java. The waste treatment has been carried out by adding alkaline to neutralize the acid conditions in the equalization basin. However, the results have not met the requirements. It is necessary to vary the pH (8.5; 9.0; 9.5; 10.0 and 10.5) to precipitate of Zn optimally, modify the dose of coagulants (50; 100 and 150 mg/L) and reaction times (10; 15 and 20 minutes) to reduce its turbidity and COD concentration. The best results were obtained at a pH of 9.5 with a coagulant dose of 50 mg/L and a reaction time of 10 minutes. This condition can reduce Zn concentration (79 to 3.71 mg/L), turbidity (557 to 1.42 NTU), COD (222 to 68 mg/L) with a removal efficiency of 95.3%; 99.7%; and 69.4% respectively. These values have met the standard requirements according to government regulations.

Analysis of Environmental Performances of Ferritization Method for the Treatment of Copper-ammonia Wastewater under the Optimized Condition via RSM

Copper-ammonia wastewater from industrial processes is an important form of hazardous waste that can contaminate water resources. The conventional hydroxide precipitation method used to remove copper complexes produces a large volume of unstable precipitates which still require further treatment. Ferritization is a powerful technique to remove bivalent cations from wastewater in the form of metal ferrites. This method is highly efficient in removal of metal complex ions; in addition, sludge resulting from this method is stable. The objective of this study was to investigate optimum conditions for ferritization using Response Surface Methodology (RSM). After optimal conditions were determined, the environmental performance of ferritization compared with hydroxide precipitation was compared using Life Cycle Assessment (LCA) methodology. The IMPACT 2002+ method was used to calculate midpoints and damage levels. The experiment found that the model obtained from RSM was accurate and reliable with R2=98.37, Adj-R2=96.91, Pred-R2= 91.40, S=1.45 and PRESS =110.859. The optimal conditions for the pH, reaction temperature, and reaction time were found to be 10.8, 69 ºC, and 115 min, respectively. In addition, the actual experiment showed that the efficiency of copper-ammonia removal was 98.413.18%. The LCA results indicate that hydroxide precipitation shows more impact at midpoint levels than ferritization, except for aquatic acidification and global warming effects. On the other hand, the endpoint analysis showed that the ferritization has a higher performance in regard to human health, ecosystem quality, and resource consumption. Ferritization had a greater impact on climate change than hydroxide precipitation because the process requires electricity. Without the use of recycling sludge as catalyst, the endpoint of natural resources from ferritization could be higher than for hydroxide precipitation. In conclusion, ferritization demonstrated better performance both in terms of its efficiency of copper-ammonia removal and its environmental performance.

Removal of Hg, Fe and Cr from Chemical Oxygen Demand (COD) analysis waste by hydroxide precipitation method

Wastewater from Chemical Oxygen Demand (COD) analysis is one of laboratory liquid wastes that is dangerous and potentially polluting the environment due to it contains dissolved heavy toxic metals such as silver (Ag), mercury (Hg), iron (Fe) and chromium (Cr). One of the treatment methods for removing heavy metals on a laboratory scale is precipitation method. The purpose of this research was to determine the most optimum condition for Hg, Fe and Cr removal. Hydroxide precipitation method was used with NaOH as the precipitant. The varied parameter was pH (3,7,9 and 11). Based on the results, the most optimum efficiency of metal Hg, Fe and Cr removal was observed at pH 11, reaching 99% removal efficiency for all metals.

Recovery Ion Hg2+ dari Limbah Cair Industri Penambangan Emas Rakyat dengan Metode Presipitasi Sulfida dan Hidroksida

Unlicensed gold mining activities (PETI) using mercury (Hg) as a gold element binder is called the amalgamation process. Mercury is a heavy metal toxic. The use of mercury can potentially cause pollution in environment, especially the aquatic environment. For overcoming the heavy metals mercury in liquid waste, it needs an alternative wastewater treatment method called chemical precipitation. This study is aimed to recover Hg2+ ions from liquid wastes by using sulphide precipitation and hydroxide methods. This research studied the effect of pH on Hg ions which is deposited in the precipitation process and found out the rate of Hg precipitation formation. Precipitation was done by using sodium sulphide (Na2S) 0.3 M and Ca(OH)2 0.004 M as a precipitation agent with rapid mixing speed for about 200 rpm for 3 minutes and continued with slow mixing for about 40 rpm for 30 minutes. Then, just let the liquid sample be for 24 hours to precipate the precipitate formed. The results show that precipitation method by using a Na2S solution can decrease the content of Hg in HgCl2 synthetic waste. An optimum mass of HgS precipitate of 0,0458 g was achieved pH 9 for 200 mL of wastewater liquid with a removal efficiency percentage up to 99.81%. The concentration of mercury can be derived from 130 ppm to 0.25 ppm. The rate of formation of HgS precipitate was obtained 0.0004g/ hour. While, hydroxide precipitation method can decrease mercury level up to 90,11% at pH 12 and mass of Hg (OH)2 precipitate obtained is 0,2784 g. However, the result of EDX analysis of the precipitate of Hg (OH)2 shows that the content of Hg precipitate is just 0.281%.

Structural Analysis of Magnesium-Aluminium Hydrotalcites Modified with Iron III Obtained by Hydroxide Precipitation Method

Hydrotalcite-type anionic clays are a group of important materials used in adsorption processes, mainly for organic pollutants removal due the layered double hydroxide structure. The layer-interlayer interactions provide a structural memory even after dehydration and dehydroxylation process, since a very stable interlayer anions are part of material composition, like the carbonate one. A limited numbers of trivalent modifier cations can replace the aluminium cation due the ionic radii mismatch or oxidation state restrictions. Transition metal cations can replace the aluminium one in octahedral site of hydroxide lamellas in order to improve the adsorptive behaviors. In this work, we have investigate three compositions of carbonated magnesium-aluminium hydrotalcite with dif-ferent iron (III) contents through the co-precipitation method at pH 11 and aging step at 60°C for 6 hours. Thermal analysis was performed aiming the determination of the hydration water and hydroxyl amounts in dried precipitate samples, taking in account the results obtained for X-ray diffractometry, infrared spectroscopy, and nitrogen adsorption-desorption characterization for several thermally treated samples. All of synthesized samples showed high surface areas, even for high temperature of thermal treatment. The co-substitution with iron (III) reduced the temperature of dehydration and dehydroxylation process, but the co-substitution at 5 mol% provides other desirables characteristics, like a more amount of rhombohedral HDL phase and higher porosity, even after the thermal treatment at 500°C for 4 hours. This result makes that composition very applicable as a reusable adsorbent material in order to removal several types of micro-pollutant compounds in aqueous media.

Feasibility and enhancement of copper and ammonia removal from wastewater using struvite formation: a comparative research

AbstractBACKGROUNDCopper–ammonia‐containing wastewater is widely generated in various industrial sectors, such as semiconductor production, printed circuit board (PCB) manufacturing, surface finishing, and electroplating processes. Three chemical precipitation methods, i.e. hydroxide precipitation, sulfide precipitation and struvite formation for treatment of chelated copper–ammonia wastewater have been comparatively evaluated.RESULTSThe conventional hydroxide precipitation method possessed the highest copper and ammonia removal at 60.5% and 9.7%, respectively. Although sulfide precipitation decomposed the copper–ammonia complex with the high copper removal of 98.5%, the ammonia removal was just 14.0%. The struvite formation method was demonstrated to be effective for enhanced simultaneous copper and ammonia removal with efficiencies of 99.9% and 98.8%, respectively. UV–vis analysis indicated that the struvite formation method also decomposed the copper–ammonia complex ion. Using XPS and XRD spectra, struvite and cupric hydroxide were shown to be formed after the addition of magnesium and phosphate (with molar ratio n(Mg:P):n(NH3‐N) ranging from 1.0–1.2:1). The larger particle size of the precipitates in the struvite forming process and the enhanced settling property indicated the binding interaction between Cu(OH)2 and struvite which enhanced the sedimentation and finally contributed to the simultaneous and highly efficient removal of copper and ammonia from the recalcitrant chelated wastewater.CONCLUSIONThe struvite formation method performs far better than hydroxide precipitation and sulfide precipitation methods. Binding interaction between cupric hydroxide and struvite enhanced the performance. This study provides some guidance on application of the struvite formation method for the simultaneous removal of heavy metal and ammonia from polluted water. © 2016 Society of Chemical Industry

Evolution of physicochemical and electrocatalytic properties of NiCo2O4 (AB2O4) spinel oxide with the effect of Fe substitution at the A site leading to efficient anodic O2 evolution in an alkaline environment

Within the framework of this work, spinel-type ternary transition metal oxides of nickel, cobalt and iron with the composition FexNi1−xCo2O4 (0 ≤ x ≤ 1) were prepared and tested as promising electrocatalysts for the oxygen evolution reaction (OER) in alkaline water electrolysis. The hydroxide precipitation method was used for the synthesis. The morphology, structure and specific surface area of the prepared electrocatalysts were determined by means of scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, the Brunauer Emmet Teller method and X-ray photo electron spectroscopy. The electrochemical properties were tested by thin-film technique on a rotating disk electrode and in a single-cell laboratory water electrolyzer coupled with electrochemical impedance spectroscopy. The OER studies indicate that substitution of Ni by Fe increases the electrocatalytic activity of the resulting material significantly. The highest activity was achieved for x = 0.1. Whereas the current density obtained using a pure nickel anode in the water electrolysis test was 54 mA cm−2 at a cell voltage of 1.85 V, in the case of the anode modified with NiCo2O4 catalyst the value was 87 mA cm−2. Using ternary transition metal oxides in the water electrolysis test and under identical conditions, the catalyst with the highest activity displayed a current density of 115 mA cm−2.

구리, 니켈, 코발트, 철 혼합용액(混合溶液)으로부터 구리의 제거(除去)

니켈, 코발트와 철의 혼합용액에 미량 함유되어 있는 구리 (399 ppm 구리, 208 ppm 철, 15.3 g/L 니켈, 2.1 g/L 코발트)를 분리, 제거를 위한 방법들을 검토하였다. 중화침전법의 경우 용액의 pH가 7.0 에서 구리는 철과 함께 전부 수산화물로 침전, 제거되었으나 니켈과 코발트의 일부도 함께 침전되었다. 황화침전법의 경우 1.25% 농도의 <TEX>$Na_2S$</TEX>를 구리의 2당량비 첨가하고 용액의 pH가 1.0인 경우 구리가 99.7% 제거 되었다. TP207 양이온 흡착제를 사용한 이온교환수지법은 평형 pH 2.0 에서 구리만이 선택적으로 흡착되었으며 탈착용액으로는 5% 황산이 적당하였다. The methods to separate and remove copper in the mixed solution ((399 ppm Cu, 208 ppm Fe, 15.3 g/L Ni, 2.1 g/L Co) with nickel, cobalt and iron were investigated. With hydroxide precipitation method, copper and iron ions were completely precipitated and removed from the solution at pH 7 while some nickel and cobalt also were precipitated. 99.75% copper could be precipitated and removed as copper sulfide from the solution with adding <TEX>$Na_2S$</TEX> (1.25 w/v concentration) of 2 times equivalent of Cu at pH 1. Copper was selectively absorbed on TP 207 ion exchange resin at equilibrium pH 2.0 and could be eluted from copper-loaded resin using 5% <TEX>$H_2SO_4$</TEX>.

A comparative study on surface morphological investigations of ferric oxide for LPG and opto-electronic humidity sensors

In the present work nanostructured ferric oxides were synthesized via hydroxide precipitation method without using any surfactant and size selection medium. The surface morphologies and structure of samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The structural analysis confirmed the formation of Fe2O3 with α-phase and rhombohedral structure. Optical and thermal properties were investigated by using UV–visible absorption spectroscopy and differential scanning calorimetry (DSC) techniques. Pelletizations of materials were done using hydraulic press and these pellets were investigated with the exposition of liquefied petroleum gas. Variations in resistance of the pellet with time for different concentrations of LPG were recorded at room temperature (27°C). The maximum value of average sensitivity was found ∼5 for 5vol.% of LPG. Our results show that the LPG sensing behavior was inspired by the different kinds of surface morphologies of Fe2O3 and inferred that the spherical porous nanoparticles synthesized via hydroxide precipitation process (S-3) had best response to LPG.

High rate performances of the cathode material LiNi 1/3Co 1/3Mn 1/3O 2 synthesized using low temperature hydroxide precipitation

A low-temperature reaction route is introduced based on hydroxide precipitation method to synthesize the cathode material LiNi 1/3Co 1/3Mn 1/3O 2. The crystal structure and morphology of the prepared powder have been characterized by X-ray diffraction and Scan electron microscope, respectively. The charge–discharge tests were performed between 2.5 and 4.5 V. The discharge capacity of the material is strongly impacted by the reaction temperature. The powders sintered at 850 °C show the best electrochemical performance and the initial discharge capacity is about 160 mAh g −1 at 5 C. Powder X-ray diffraction and Scan electron microscope results reveal that the excellent electrochemical performances should be ascribed to the lower precursor reaction temperature, the lower degree of cation mixing and analogous spherical small particles, which can improve the transfer of Li ions and electrons. All these results indicate that this material has potential application in lithium-ion batteries.

Remediation of Heavy-Metal-Contaminated Soil with Chelating Agent and Treatment of Waste Solution

Experiments have been performed to elute and remove contaminants from artificially contaminated soil using chelating agents such as citric acid, which exists in nature, and N,N-dicarboxymethyl glutamic acid (GLDA), which is biodegradable. The soil was artificially contaminated with heavy metals such as lead, copper, and cadmium. The most effective conditions for batch elution operation using citric acid alone were determined to be 0.1 mol/dm3, pH 3–4, and 30 min shaking time. Since the elution of Pb tended to be slower than that of the other heavy metals, it was determined that this process could be accelerated by adding GLDA to the citric acid. This mixed chelating agent was then used in the column continuous test, which was carried out in order to obtain the elution speed and flow amount required to satisfy the environmental quality standard values regarding contaminated soil. Based on the elution speed obtained from the column operation, guidelines for designing a heap leaching type treatment of contaminated soil are proposed. Treatment of waste solution was investigated using sulfide and hydroxide precipitation methods to remove heavy metal ions. Metal sulfide precipitation method is superior for the removal of metal ions in the presence of citric acid and there seems to be a possibility to reuse chelating agents after removal of metal ions.

Effect of V substitution at B-site on the physicochemical and electrocatalytic properties of spinel-type NiFe 2O 4 towards O 2 evolution in alkaline solutions

Spinel-type ternary transition metal oxides of nickel, iron and vanadium with composition NiFe 2 − x V x O 4 (0 ≤ x ≤ 1) have been synthesized by a hydroxide precipitation method and investigated for their physicochemical and electrochemical catalytic properties towards the oxygen evolution reaction (OER) in alkaline solutions at 25 °C. The OER study indicates that substitution of V from 0.25 to 1.0 mol for Fe in the spinel matrix increases the electrocatalytic activity of the oxide greatly; the activity being the greatest with x = 0.5 mol. At low overpotentials, the Tafel slope and the order for the OER with respect to OH − concentration were found to be ∼40 mV and ∼2, respectively.

Er‐Doped Y2O3 Nanoparticles: A Comparison of Different Synthesis Methods

Nanoparticles of erbium‐doped yttria (Er:Y2O3) are important precursors to transparent ceramics for high‐power solid‐state lasers systems. As structure influences properties and, subsequently, performance the purpose of this work is to compare the morphological and chemical nature of the nanoparticles synthesized using two common methods: solution precipitation and combustion synthesis. A thorough characterization of as‐prepared and calcined powders was performed using Fourier transform infrared spectroscopy, X‐ray diffraction, conventional and high‐resolution transmission electron microscopy, and Brunauer–Emmet–Teller methods. Solution precipitation was found to lead to two different precursor compositions (yttrium carbonate or yttrium hydroxide) depending on the precipitating reagent whereas combustion synthesis yielded only phase‐pure, cubic Er:Y2O3. The hydroxide precipitation and combustion synthesis methods exhibited agglomerated particles with low surface area after calcining the precursors at 900°C. The addition of a small amount of ammonium sulfate during combustion synthesis was found to reduce the level of agglomeration, resultant particle size, and degree of crystallinity of the calcined Er:Y2O3 nanoparticles. The amount of carbon dioxide (CO2) and water (H2O) on the surface of the Er:Y2O3 powders is dependent on the powder surface area, however, increasing levels of gas absorption on the particle surfaces do not have a detrimental effect on the sinterability. The sintered density increases with increasing surface area and decreasing agglomeration.

Heavy Metals Removal by Hydroxide Precipitation and Coagulation-Flocculation Methods from Aqueous Solutions

Abstract The hydroxide precipitation and coagulation-flocculation methods were used to treat wastewater containing lead, zinc, copper, and iron. The concentrations of heavy metals in the synthetic wastewater range from 1 to 14 mg/L for lead, 5 to 90 mg/L for zinc, 3 to 90 mg/L for copper and 5 to 45 mg/L for iron. Individual Zn(II) and Cu(II) with concentrations below 90 mg/L and Fe(III) with concentrations below 45 mg/L were removed up to 99% by the precipitation method in the pH range of 8.7 to 9.6, 8.1 to 11.1, and 6.2 to 7.1, respectively. Though the highest percent removal of Pb(II) by hydroxide precipitation alone was approximately 98%, the final dissolved concentrations did not fulfill the Standard A discharge limit required by the regulations, thus further treatment by the coagulation-flocculation process was performed. Aluminum sulphate (alum), polyaluminum chloride (PACl) and magnesium chloride (MgCl2) have been used as coagulants together with Koaret PA 3230 as coagulant aid to determine the effectiveness of the coagulation method for the removal of individual heavy metals in the wastewater. The effects of parameters such as pH, type, and dosage of coagulant on the percentage of metal removal, and the amount of coagulant aid on the flocs settling time were investigated. The jar test showed that up to 99% removal of Pb(II) was attained by the addition of 1,200 mg/L of alum, 150 mg/L of PACl, and 2,000 mg/L of MgCl2 in a pH range of 6.5 to 7.8, 8.1 to 8.9, and 9.7 to 10.9, respectively.