Adsorption of Humic Acid from Water Using Chemically Modified Bituminous Coal-based Activated Carbons (original) (raw)
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Linnaeus Eco-Tech, 2017
Humic acids (HA) constitute the major fraction of natural organic matter in water supplies. HA are very problematic with regard to drinking water treatment and supply since, not being completely removed by conventional treatment processes, they react with chlorine resulting in formation of carcinogenic and regulated disinfection-by products. Adsorption of brown (BHA) and gray (GHA) fractions of humic acid on starting and modified mesoporous activated carbons was investigated. BHA and GHA are fractions of humic acid extracted from young brown coal (Czech Republic) which differ essentially in their characteristics in terms of structure and physicochemical properties. Mesoporous activated carbon was modified by two ways: ammonization (AC/N) and high-temperature hydrogen treatment (AC/H). All activated carbons studied, showed higher adsorption capacity towards BHA comparing to GHA, what is attributed to the smaller molecular weight of BHA molecules, as determined by ultrafiltration meth...
Emergent Materials, 2020
The adsorption of humic substances on three different adsorbents was investigated and adsorption isotherms were applied in this research. The three adsorbents studied include granular activated carbon (GAC), ferric oxihydroxide in its beta form (β-FeOOH) and iron-coated activated alumina (AAFS). Physical and chemical characteristics of the adsorbents were also fully investigated. Calcium was added to the HS solution in order to represent water with a hardness equivalent to water hardness typically found in London (UK). The examination of the GAC indicated a large microporous area with lower surface area associated with meso- and macropores. The AAFS and β-FeOOH did not present any microporous area. The overall surface area was high for GAC (980 m2 g−1) but lower for AAFS (286 m2 g−1) and β-FeOOH (360 m2 g−1). The Freundlich isotherm model was fitted to all adsorbent–adsorbate systems. It was shown that GAC offered a large adsorption capacity for removal of low molecular weight humic...
Adsorption of humic acid by powdered activated carbon in saline water conditions
Desalination, 2003
The adsorption of humic acid (HA) by powdered activated carbon (PAC) in saline waters has been examined in the absence and presence of metal salt coagulants. The study showed that adsorption of HA by PAC can be significantly greater in saline water compared to freshwater and low conductivity water. An optimal adsorption was attained at saline concentrations corresponding to synthetic seawater diluted to 12.5-25% of its original concentration. In undiluted synthetic seawater the adsorption of HA from solution by PAC was comparable with that of local tap water in terms of initial adsorption rate and total removal. The enhanced adsorption is believed to be a combination of reduced electrostatic repulsion between the HA and PAC at high salt concentrations, and chemisorption due to chemical bonding between the functional groups. The effects of adding a metal salt coagulant, either aluminium sulphate or ferric chloride, on overall HA removal were found to depend strongly on the coagulant dose, solution pH and the sequence of addition of the PAC and metal salt coagulant. Addition of the PAC shortly before the coagulant was found to give the greatest removal of HA.
Modification of Activated Carbon for the Adsorption of Humic Acid
Adsorption Science & Technology, 2015
Commercial activated carbon treated with sulphuric and phosphoric acids was used to remove humic acids (HAs) from water. To achieve this goal, the iodine indices of treated and untreated materials were characterized by X-ray diffraction and nitrogen physisorption. Adsorption assays for HAs evaluated the quantities adsorbed after a fixed time. Temporal evolution of HA adsorption was determined from the adsorption kinetics. Experimental results indicated that the sulphuric acid treatment was more efficient and had a higher HA adsorption at each time point evaluated. Evaluating the specific area helped to verify this fact, reflecting the number of mesopores in the used material.
International Journal of Advanced Science and Engineering, 2024
This study focuses on a comparative analysis of pretreated coal effluent with Hydrochloric (HCl) and Tetraoxosulphate (VI) Acids (H2SO4) activated carbon. The study is motivated by the discrepancies existing in the removal efficiency of particulate matter from effluent samples, using adsorbents that are activated by different acids of varying strengths. A sample of cow bone collected from a functional abattoir in Niger State, Nigeria, was subjected to acid activation of HCl and H2SO4 using standard procedures, for coal effluent treatment purposes. The solutions of adsorbent samples were analyzed for pH, electrical conductivity, total hardness, and total alkalinity, to determine their potential adsorptive strength. The results showed that pH values for 0.2 M fell between 7.20 – 7.70 for HCl-treated adsorbent and 5.94-7.25 for H2SO4-treated adsorbent. However, for 0.5 M solution showed, the pH was between 6.20-7.96 for HCl-treated adsorbent and 5.95 – 6.72 for H2SO4-treated adsorbent, while at 1.0 M solution, the fell between 6.10-8.18 for HCl-treated adsorbent and 5.95 – 6.80 for H2SO4-treated adsorbent. The hardness analysis showed that the HCl-treated adsorbent recorded a maximum hardness of 240 mg/l at molarity level of 1.0 M, while the H2SO4-treated adsorbent gave a maximum hardness of 220 mg/l at a molarity level of 0.2 M. The total alkalinity for HCl-treated adsorbent (for the molarity levels (60-120 mg/l) was found to be higher than that of H2SO4-treated ones (60-80mg/l). Also, the results of electrical conductivity favoured the H2SO4-treated adsorbent (with a maximum conductivity value of 452 μs/cm at 0.2M) more than the HCl-treated one (which has maximum conductivity of 448 μs/cm at 1.0M). Consequently, the results indicate that the H2SO4-treated adsorbent has an enhanced activation, for better surface particulate removal compared to the HCl-treated adsorbents.
Journal of Hazardous Materials, 2006
Binding of Zn 2+ and Cd 2+ cations to relatively young brown coals YBC (lignite), humic acids (HAs) and commercial humic acid (CHA) were studied in aqueous media at pH 2.7-6 by polarographic method. This study was conducted to evaluate the removal of heavy metals in an aquatic system without prior treatment. The general principles of cation binding to YBC and humic materials are discussed. Sorption of heavy metal ions (Zn 2+ and Cd 2+) on samples of YBCs from three areas (Ilgin, Beysehir, and Ermenek) in the vicinity of the city of Konya in Anatolia (Turkey) were compared with sorption of these metal ions on HAs, prepared from these YBCs. The ability of both types of sorbent to remove metals from aqueous solutions was studied as a function of pH and concentration of initial metal solutions. Sorption depends strongly on pH, the origin of the YBC and on the nature of the metal ion. Whereas, for YBCs the main ligand groups seem to be carboxylate ions, this is not the case for the HA polymers, prepared from three YBCs, which differ substantially from properties of commercial samples of "HA". The process is very efficient especially in the case of low concentrations of pollutants in water, where common methods are either economically unfavorable or technically complicated. Of the two metal ions examined, Cd 2+ was found to form the most stable HA complexes, followed by Zn. Effective removal of metals was demonstrated at pH-values of 5-5.7. The adsorption isotherm was measured at 25 • C, using adsorptive solutions at the optimum pH-value to determine the adsorption capacity. An important aspect of the proposed method was that the removal was performed on several metals at a pH-range in which a given metal undergoes an adsorption process making the method useful for wastewater treatment.
Adsorption, 2014
The effects of the humic acid (HA) nature and the activated carbon (AC) surface chemistry on the effectiveness of HA removal were investigated. Brown (BHA) and gray (GHA) humic acid fractions of different structure and physicochemical properties were tested in the adsorption process using mesoporous ACs. The modification of chemical structure and surface properties of AC was achieved by ammonization (AC/N) and hydrogen treatment (AC/H). Both approaches led to a decrease in the oxygen content followed by an increase in the carbon basicity, maintaining the porous texture of AC nearly unaltered. Over twice higher removal degree of BHA and GHA was observed for the modified ACs. The kinetics of adsorption of HA fractions have been discussed using the pseudosecond-order model and the intraparticle diffusion model. All ACs showed a higher adsorption capacity toward BHA compared to GHA, which is mainly attributed to the lower molecular weight of BHA. The shape of the equilibrium isotherms indicates a strong competition between water and HA molecules for adsorption sites of the carbon surface.
A B S T R A C T Natural (rice husk) and artificial (mesoporous carbon) materials were mechanochemically treated with humic acid to obtain humic-modified sorbents. The obtained sorbents were characterized by elemental analysis, surface area analysis, FTIR-spectroscopy, and acid–base titrations. Although the specific surface area of the carbon-humic material was significantly higher than that for the husk-humic material, the total number of surface functional groups for both materials was almost the same (approximately 2.0 mmol/g). The effect of the modification on Cd(II) sorption was evaluated at different pH values. The equilibrium data fit to the Langmuir model of sorption. The maximum sorption capacity of both modified sorbents increased with increasing pH values from 5 to 8 and reached approximately 41 mg/g at pH 8. Primarily carboxyl groups define the main contribution towards Cd(II) sorption whereas the basic amino groups are involved in the binding of cadmium at pH above 7. The modified sorbents can be reused after Cd(II) desorption with 0.05 M HNO 3. The efficiency of Cd removal and recovery remains constant at least in 5 consecutive cycles. The results obtained demonstrate that both humic-modified sorbents have potential for Cd(II) removal and recovery from contaminated wastewater.
Effect of the mineralization on removing the humic substances by adsorption on activated carbon
DESALINATION AND WATER TREATMENT, 2017
It is well known that the reactivity of chlorine with the humic substances results the formation of organohalogens in particular trihalomethanes suffering having chronic toxicity (mutagenic and/or carcinogen). These compounds, if they are formed no treatment can eliminated them. In this context, the aim of our work is to test the performance of powder activated carbon on removing the humic substances in the various mediums of mineralization. The adsorption testing is performed in batch by adopting different operating conditions. We thus evaluated various parameters relating to adsorption laws who will inform us about the retention capacity of the adsorbents with respect to humic substances of the water tested. The physicochemical characteristics of the water tested were also determined. The results have shown that the tested water is characterized by a more or less important mineralization and the quality varies from very good to poor. The adsorption tests showed that the removal of humic substances on carbon activated powder is more or less important, according to the mineralization of water. The yields obtained ranging 92.10%-100% with an equilibrium time vary from 30 to 240 min. According to all the results that we obtained, we also suggest that mineralization has notable influence on the adsorption process, either globally or through the mineral elements present. Similarly, the origin and nature of the humic material, the particle size and the distribution of pores adsorbents, as well as the physicochemical characteristics of the medium significantly affect the removal efficiency of humic substances. The effectiveness of these adsorbents and the increasing of adsorption capacity were clearly appeared through the exploitation of our results by the Freundlich and Langmuir isotherms.