Experimental study of lead (II) removal using polymorphous silica adsorbents

The Kwoiek Area of British Columbia contains a pendant or screen of metamorphosed sedimentary and volcanic rocks almost entirely surrounded by a portion of the Coast Range Batholith, and intruded by several dozen stocks. The major metamorphic effects were produced by the quartz diorite batholithic rocks, with minor and later effects by the quartz diorite stocks. The sequence of important metamorphic reactions in the metasedimentary and metavolcanic rocks, ranging in grade from chlorite to sillimanite, is: 1. chlorite + carbonate + muscovite → epidote + biotite 2. chlorite + carbonate → actinolite + epidote 3. chlorite + muscovite → garnet + biotite 4. chlorite + epidote → garnet + hornblende 5. chlorite + muscovite → garnet + staurolite + biotite 6. chlorite + muscovite → aluminum silicate + biotite 7. muscovite + staurolite → garnet + aluminum silicate + biotite 8. staurolite → garnet + aluminum silicate Continuous reactions, occurring between reactions 5 and 7, are: A. chlorite + (high Ti) biotite + Al2O3 (from plagioclase?)→ garnet + staurolite + (low Ti) biotite + O2 B. muscovite (phengitic) → garnet + staurolite +muscovite (less phengitic) + O2 (?) Detailed electron microprobe work on garnet, staurolite, biotite, and chlorite shows that: (1) The garnet porphyroblasts are zoned according to a depletion model, called the Rayleigh depletion model, which assumes equilibrium between the edge of a growing garnet and the minerals which are unzoned, notably biotite, chlorite, and muscovite, but which assumes disequilibrium within the garnet. (2) The staurolite porphyroblasts are also zoned, and from their zoning patterns reactions A, B, and 5 are documented. Progressive reduction of iron with increasing grade of metamorphism is also inferred from the staurolite zoning patterns. (3) During a late period of falling temperature garnet continued to grow and the biotite and chlorite reequilibrated. The biotite, chlorite, and garnet edge compositions can vary from point to point in a given thin section, indicating that the volume of equilibrium at the final stage of metamorphism was only a few cubic microns. (4) The horizon within the garnet that grew at maximum temperature can be identified. The Mg/Fe ratio of this horizon, if the garnet composition is a limiting composition in the Al2O3 - K2O - FeO - MgO tetrahedron, increases systematically with increasing metamorphic grade. Biotite and chlorite compositions also show a general increase in Mg/Fe ratio with increasing metamorphic grade, but staurolite appears to show the reverse effect. (5) The Mg/Fe ratio at the maximum temperature horizon of the garnet porphyroblasts is a function of its Mn content as evidenced from the study of five garnet-bearing rocks, collected from one outcrop area, with the same assemblage but with differing proportions of minerals. An important implication of zoned minerals is that the effective composition of a system in a phase lies on the join between the homogeneous minerals (if there are two) and not within three-or- four-phase fields when a zoned mineral, such as garnet or staurolite, is present in the assemblage. Study of the three aluminum silicates found in the Kwoiek Area showed that a constant pressure change in polymorphs from andalusite to kyanite to sillimanite took place with increasing temperature. This transition series is best explained by the metastable formation of andalusite. Photographic materials on pages 15, 121, 160, 162, and 164 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.

Removal of Pb2+ ions by raw corn silk (Zea mays L.) as a novel biosorbent

Treatment of wastewater from heavy metal pollutants still remains a serious challenge for some developing countries without centralized waste water systems. The study examines the potentials of raw and nano composite from Spondias mombin seed as an adsorbent for removal of lead (II) ions from contaminated water. Instrumental techniques such as scanning electron microscopy (SEM), Fourier Transform Infrared Spectrophotometer (FTIR), and Atomic absorption Spectrophotometer (AAS) were used to characterize the absorbents. The study analyzed the effect of various factors including absorbent dosage (0.2 – 1.0g), lead concentration (100-300 mg), contact time (30-180 min), pH (2-10) and temperature (30-50°C) respectively, on the absorption of pb2+ ions. The experimental findings revealed that the adsorbents have high absorption capacity and high percentage removal for the removal of pb2+ ions from aqueous solutions. Absorption isotherm kinetic models and thermodynamic studies were applied to access the absorption mechanism of lead (II) ion removal. The Langmuir absorption isotherm and pseudo-second-order model were found to fit the equilibrium data for nano composite while Freundlich isotherm and pseudo-first-order fitted the equilibrium data for raw fruit. According to the results obtained, a linear model was generated which indicated good predictability and the results agreed with the experimental data. The contact time and absorbent dosage were predicted to have a positive effect on the absorption process. However, after the investigation on the efficiency of raw and nano composite of Spondias mombin fruit on the removal of lead (II) ion from aqueous solutions as the impact of different variables were investigated. The study showed that the raw and modified adsorbents can be considered effective adsorbent for the removal of lead metal ions from wastewater by varying some basic parameters. The physiochemical properties of the absorbent were analyzed and the results obtained confirmed the adsorption potentials of the raw and nano composite. The removal efficiencies of both adsorbents on the Pb2+ ion were strongly dependent on their contact time, initial metal ion concentration, absorbent dosage, pH and temperature. The Langmuir isotherm model was well fitted to the experimental data, indicating that the two absorbents were effective in removing Pb2+ ions from aqueous solutions with low absorption energy. The experimental data of Pb2+ ions adsorption by raw and nano composit adsorbents studied were fitted with the pseudo-first-order and pseudo-second-order kinetic model respectively, revealing that adsorption occurs by physiosorptions and chemisorptions technique. The thermodynamic data showed that the adsorption process was exothermic, spontaneous and feasible in nature. Therefore, this work exposed the possible removal of lead (II) ions by raw and nano composite from agro waste of Spondias mombin from wastewater, which is generally a low cost agro waste.

Discharge of heavy metals from metal processing industries is known to have adverse effects on the environment. Biosorption of heavy metals by metabolically inactive biomass of microbial organisms is an innovative and alternative technology for removal of these pollutants from aqueous solution. Presence of heavy metals in the aquatic system is posing serious problems and zinc has been used in many industrials and removal of Zn ions from waste waters is significant. Biosorption is one of the economic methods that is used for removal of heavy metals. In the present study, the biomass generated from the dried Chlorella pyronoidsa was used for evaluating the biosorption characteristics of Zn ions in aqueous solutions. Batch adsorption experiments were performed on these leaves and it was found that the amount of metal ions adsorbed increased with the increase in the initial metal ion concentration. In this study effect of agitation time, initial metal ion concentration, temperature, pH and biomass dosage were studied. Maximum metal uptake was observed at pH = 5. Maximum metal uptake (qmax) was 101.11 mg/g. The biosorption followed both Langmuir and Freundlich isotherm model. The adsorption equilibrium was reached in about 1 h. The kinetic of biosorption followed the second – order rate. The biomass could be regenerated using 0.1 M HNO3. A positive value of ∆H° indicated the endothermic nature of the process. A negative value of the free energy (∆G°) indicated the spontaneous nature of the adsorption process. A positive value of ∆S° showed increased randomness at solid–liquid interface during the adsorption of heavy metals, it also suggests some structural changes in the adsorbate and the adsorbent.Fourier transform infrared (FTIR) spectrums of C. pyrenoidosa revealed the presence of hydroxyl, amino, carboxylic and carbonyl groups. The scanning electron micrograph (SEM) clearly revealed the surface texture and morphology of the biosorbent. Key words: Biosorption, Chlorella pyronoidosa, Zn, isotherm models, kinetic.

Present of pharmaceutical as the emerging pollutants arise the concerns of environment community regarding the potential impact of acetaminophen (ACT) on ecological and human health. Adsorption process has been proven as an effective treatment being activated carbon as the adsorbent to remove many types of pollutant including low concentration of pollutants. However, on large scale industrial processes, utilisation of activated carbon is limited because of their high production cost. Synthesis of waste materials as a precursor of adsorbent is an attractive approach in sustainable management and economic availability. In this study, the removal of ACT from aqueous solution by chemically treated chicken bone (AC) waste was investigated. The adsorption process was conducted in a batch adsorption and affected by several experimental parameters including contact time, pH, adsorbent dose, initial concentration and temperature. With AC dosage of 0.1 g about 93 % of 1,000 mg/L ACT was removed from the aqueous solution that had pH of 2 and temperature of 25 °C. Kinetic of ACT adsorption was well described by pseudo-second order kinetic model. Meanwhile, effect of initial concentration of acetaminophen adsorption data was fitted well with Freundlich isotherm model withan R2 of 0.9909. Finally, the data obtained from effect of temperature was used to determine the adsorptionthermodynamic including the enthalpy, ?H, Gibbs energy, ?G and entropy, ?S. It was found that the ?G was negative at all temperature while both, ?H and ?S was also negative between temperatures of 25 °C to 70 °C indicating the process of ACT adsorption was exothermic reaction and the adsorption reaction is spontaneous at low temperature.

In this work, cobalt-methylimidazolate framework has been used as an adsorbent in the removal of Pb(II) from acid mine drainage in adsorption batch system. X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer-Emmet-Teller and transmission electron microscope were used for structural, morphological, and surface characteristics of cobalt-methylimidazolate framework. The concentration of heavy metal ions in water samples was measured by inductively coupled plasma optical emission spectrometry. Different experimental factors/variables (such as contact time, dosage, and pH) affecting the adsorption of Pb(II) from acid mine drainage were optimized by response surface methodology based on central composite design. Under optimized experimental parameters, the maximum adsorption capacity of Pb(II) was found to be 105mgg-1. The nature of the adsorption process was investigated using Langmuir and Freundlich isotherm models. The obtained data best fitted Langmuir isotherm model suggesting a homogeneous adsorption process. Furthermore, the adsorption mechanism was investigated using five kinetic models, that is, pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich model. The adsorption data fitted better to pseudo-second-order followed by intra-particle diffusion kinetic models suggesting that the adsorption mechanism is dominated by both chemical and physical adsorption processes. The adsorbent could be regenerated up to 8 cycles and it was successfully used in the removal of lead in real acid mine drainage samples.

The PALMEIROPOLIS Cu-Zn (Pb) volcanogenic massive sulfide deposit, Brazil, consists of three ore bodies enclosed by hydrothermal alteration zones. The ore bodies and the alteration zones were metamorphosed under amphibolite fades conditions. The Palmeirdpolis alteration zones are characterized by a great diversity of bulk rock composition that originated a wide variety of low variance mineral assemblages. These assemblages are composed of orthoamphiboles (anthophyllite and gedrite), hornblende, biotite, garnet, staurolite, sillimanite, gahnite and, rarer, cordierite. Based on analyses of mineral chemistry aad mineral assemblages, temperatures are estimated to have been 550 - 625°C and pressures 2 - 5.5 kbar. The temperature of metamorphism that prevailed at the Palmeirdpolis deposit is comparable to other amphibolite fades massive sulfide deposits, such as Geco and Linda, Canada; Falun, Sweden; and Bleikvassli, Norway. The mineralogy of the alteration zones is similar in all these deposits even though they were metamorphosed at different pressure conditions, reflected by the crystallization of one of Al2 SiO5 phase (andalusite, sillimanite or kyanite).

Lead (Pb) present in water at high levels causes a serious problem in many places all over the world. Activated carbon (AC) is employed as a low- cost alternative adsorbent in wastewater treatment for removal of heavy metals, acid dyes and even odour. The objective of this study was to assess the potential of activated groundnut shell as an adsorbent for removal of Lead from aqueous Lead (II) Chloride solutions using batch experiments. The groundnut shells were impregnated with activating reagents and subsequently heated to obtain activated groundnut shells. From the results the adsorption of Lead was optimal at contact time of 65 minutes, pH of 5, an adsorbent dose of 0.6 g, initial metal ion concentration of 50 ppm, and temperature of 65ºC with an adsorption removal of 18.425%. Langmuir isotherm is the best adsorption isotherm with R2= 0.9601. From FTIR experiment, there was a participation of –OH, and –NH groups in the uptake of metals. The Gibbs free energy value of –13,391.800 J·mol⁻¹ confirms that the adsorption process is spontaneous. Furthermore, analysis of the Dubinin–Radushkevich (D–R) isotherm revealed mean free energy values (E < 8 kJ·mol⁻¹), which are characteristic of physisorption, thereby indicating that the adsorption mechanism proceeds predominantly through physical interactions rather than chemical bonding. This study advances a simple and low-cost alternative adsorbent for removal of lead from waste waters.

Aims: This study investigates the potential of chitin shrimp shells for the removal of arsenic (V) and zinc (II) ions from aqueous solutions. Materials and Methods: In this study, the chitin was extracted from shrimp shells for arsenate and zinc ions removal from aqueous solutions. The effects of pH, adsorbent dosage, contact time and initial metal ion concentration on As (V) and Zn (II) removal were investigated in a batch system. Results: The equilibrium data were described using the Langmuir and Freundlich isotherm models. The Langmuir equation was used to find the maximum adsorption capacity for arsenate (11.574 mg/g) and Zn (270.27 mg/g). Biosorption was found to depend significantly on the pH of the solution and is optimal at pH values of 4 and 7. To determine the rate-controlling mechanism for metallic ion adsorption, pseudo-first-order and pseudo-second-order equation kinetic models were tested with experimental adsorption kinetic data. Modeling results revealed that As (V) and Zn (II) kinetics data were successfully described using pseudo-first and second-order models, respectively. FTIR analyses showed that hydroxyl and carboxyl groups could be very effective for capturing these metals. Conclusion: Results showed that the chitin is a good adsorbent for the removal of arsenate and zinc ions from aqueous solutions.

Adsorption of inorganic and organic arsenic from aqueous solutions by polymeric Al/Fe modified montmorillonite

This paper aims to disclose the adsorption and anoxic degradation processes of three typical polycyclic aromatic hydrocarbons (PAHs) in the coastal sediments of China’s Bohai Sea region. The PAHs are naphthalene (Nap), phenanthrene (Phe) and pyrene (Pyr). Several sediments samples were collected from Qinhuangdao Port, and subjected to adsorption and biodegradation experiments. Then, pseudo-first-order and pseudo-second-order kinetic models were tested to explain the kinetics of liquid-solid phase adsorption systems. It is discovered that the adsorption of the three PAHs on the coastal sediments matched pseudo- second-order kinetics, revealing that adsorption processes were essentially chemical reactions. In terms of equilibrium adsorption capacity, the three PAHs are ranked as Pyr>Phe>Nap. Next, Freundlich and Langmuir models were employed to fit the experimental data. The fitting results show that the adsorption of Nap, Phe and Pyr on the coastal sediments can be explained as mono-molecular layer adsorption. All the adsorptions of Nap, Phe and Pyr were exothermic reactions. In the anoxic sediments, 93.2% of Nap was removed after 30h, 96.6% of Phe was removed after 7d, and 98.1% of Pyr was removed after 42d. The detected metabolites of Nap were [4,4-dimethyl-2-cyclohexene-1-ol], [1-carboxyl,2-hydroxy, 4-methyl-cyclohexane], the metabolites of Phe were [3-ethoxy ethyl benzoate], [Phthalate (2-methyl propyl) ester] and the metabolites of Pyr were [2- methyl succinic acid, double (2-methyl propyl) ester], [Phthalate (2-methyl propyl) ester], [Phthalic acid butyl ester, 14 alkyl ester]. The findings shed new light on the research of PAHs adsorption and anoxic degradation in coastal sediments.

In this paper, Fe3O4 and MgFe2O4 as magnetic samples were successfully synthesized by coprecipitation and combustion methods, respectively, to be used for adsorption of toxic methyl orange molecules from the aqueous solution. Characteristics of the synthesized samples were evaluated using various analyses. The results of crystalline and surface bonding assessment confirmed the successful synthesis of both samples with an appropriate structure. Moreover, Fe3O4 presented higher magnetic properties and surface area as well as lower pore diameter than MgFe2O4 sample. However, the maximum adsorption of methyl orange was obtained for MgFe2O4 (56.54 mg/g) which was around three times of Fe3O4 in the same conditions. This may be related to larger pore diameter of MgFe2O4 and the ease of access to the internal surface of the adsorbent by the adsorbate molecules. Among the evaluated isotherms, the predicted Freundlich model showed well correlation with actual results of the adsorption process and the process could kinetically explained by the pseudo-second-order equation. Thermodynamic investigation of the process showed the adsorption of methyl orange was exothermic and spontaneous. The results revealed that MgFe2O4 sample (qmax = 181.34 mg/g) can be suggested as a good adsorbent for the removal of toxic dyes and water pollutants.

The presence of chromium in aquatic streams due to the discharge of industrial effluents is of great concern because of its toxic nature. Removal of Cr(VI) ion from wastewater is a necessary task. To enhance the adsorption capacity of sawdust for heavy metals, sawdust was modified with formaldehyde and used for the adsorption of heavy metal Cr(VI). The process of modifying was characterised by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The effects of various parameters such as pH, contact time, adsorbent dose and initial metal ion concentration on the adsorption process were investigated. The maximum removal of chromium (VI) was found to be 100% at pH 2.0, initial Cr(VI) concentration of 10 mg/L, and adsorbent dose of 4 g/L. Equilibrium isotherms for the removal of Cr(VI) were analysed by the Langmuir, Freundlich, and Temkin isotherm models and the experimental data were well explained by the Freundlich isotherm model. The maximum adsorption capacity was found to be 8.84 mg/g. Kinetic studies were performed by pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich models. The R2 value of the pseudo-second-order model is higher than other kinetic models. Therefore, the obtained data were the best fit with the pseudo-second-order kinetic model. The thermodynamics indicated that the adsorption process of sawdust for Cr(VI) was endothermic and spontaneous in nature.

This study evaluates the efficiency of alkali-activated Egyptian calcium bentonite, obtained from the El Alamein region in northern Egypt, for the removal of copper (Cu2⁺), lead (Pb2⁺), and nickel (Ni2⁺) from synthetic wastewater. The bentonite samples underwent a series of preparation steps, including crushing, ball milling, magnetic separation, acid treatment with 0.1N acetic acid, and alkali activation using 5% sodium carbonate (Na2CO3). Various analytical techniques, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), cation exchange capacity (CEC) measurements, scanning electron microscopy (SEM), and free swelling analysis, were employed to characterize the materials. Absorption experiments were performed to examine the effects of pH, temperature, starting metal concentration, bentonite dose, and contact duration on heavy metal removal. The characterization results confirmed that montmorillonite was the predominant mineral in both the natural and activated bentonite samples. Adsorption studies indicated a significant improvement in heavy metal removal efficiency after activation. Under optimal conditions (pH 7, 1 g/L adsorbent dose, 120 min contact time, 20 mg/L initial metal concentration, and 20 °C), the maximum adsorption capacities of the activated bentonite were determined as 14 ± 0.03 mg/g for Cu2+, 13 ± 0.04 mg/g for Pb2+, and 12.2 ± 0.05 mg/g for Ni2+, exceeding those of the natural bentonite, which recorded capacities of 9.2 ± 0.04 mg/g, 9 ± 0.03 mg/g, and 8 ± 0.02 mg/g, respectively. Adsorption equilibrium data according to the Langmuir isotherm model, exhibiting high correlation values (R2 = 0.9979 for Cu2+, 0.9972 for Pb2+, and 0.9973 for Ni2+). Moreover, kinetic modeling demonstrated that the adsorption followed a pseudo-second-order mechanism, suggesting an intense chemisorption process. The thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, demonstrating enhanced adsorption at higher temperatures.

The paper describes the results obtained from the x-ray K-band spectra of Al for andalusite, sillimanite and kyanite. The fine structure of the aluminium K-band is correlated with the crystal structure of these minerals. It is considered that the difference between the energies of the K-and .KTjS'-lines depends on the distance between the aluminium and oxygen atoms. The energy differences between the Al and O atoms in andalusite, sillimanite and kyanite have been determined. The energy differences show a linear correlation to the known interatomic distances.