Elsevier

Journal of Molecular Liquids

Volume 290, 15 September 2019, 111181
Journal of Molecular Liquids

Effect of modification by five different acids on pumice stone as natural and low-cost adsorbent for removal of humic acid from aqueous solutions ‐ Application of response surface methodology

https://doi.org/10.1016/j.molliq.2019.111181Get rights and content

Highlights

  • Pumice stone is a natural, low-cost, available adsorbent.

  • The aim of present study was to investigate the efficacy of modified pumice with five different acids (acetic acid, hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid) for the removal of humic acid (HA) from aqueous solutions.

  • It was seen that the pumice modification by acid could considerably increase the adsorbent efficiency. The comparative effectiveness of acids on the pumice adsorbent was in the order of H2SO4 > HNO3 > H3PO4 > HCOOH> HCL.

Abstract

Pumice stone is a natural, low-cost, available adsorbent. This study aimed to investigate the efficacy of modified pumice with five different acids (acetic acid, hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid) for the removal of humic acid (HA) from aqueous solutions. Four variables were investigated: adsorbent dose (1–7 g/L), contact time (15–75 min), initial concentration (5–25 mg/L), and pH (3−11) by response surface methodology (RSM) and lab experiments. Results revealed that the amount of humic acid removal by the raw and modified adsorbents was increased by increasing the adsorbent dosage and contact time, whereas, in terms of initial concentration and pH variables, the opposite was observed. The pH and initial HA concentration had the maximum and minimum effects on the adsorption process, in all used acids, respectively. For all the adsorbents, the optimum efficiency was achieved in the following conditions: contact time = 75 min, pH = 3, pumice dosage = 7 g/L, HA initial concentration = 5 mg/L.

Additionally, it was seen that the pumice modification could considerably increase the adsorbent efficiency. The comparative effectiveness of acids on the pumice adsorbent was in the order of H2SO4 > HNO3 > H3PO4 > HCOOH> HCl. Furthermore, the data fitting using different isotherm models and adsorption kinetics specified that the data were following Langmuir and Freundlich isotherms and pseudo-second-order kinetics. The data fitting using D-R isotherm similarly revealed that the HA adsorption process was physical on all the adsorbents. This study demonstrated that the acid-modified pumice could be utilized as an economic, naturally available adsorbent for the HA removal.

Introduction

Natural organic matters (NOM) in surface water resources are the most common amphiphilic compounds, most of which consists of humic substances [1]. Humic substances are soluble organic polyetherolite that are formed from the decomposition of plant and animal residues in aqueous environments [2,3]. Structurally, humic acid substances are a broad mixture of macromolecules with yellowish to black and generally heterogeneous appearance. They comprise carbon, oxygen, hydrogen and, occasionally, a low amount of nitrogen, phosphorus, and sulfur [4]. Their solubility in aqueous environments depends on the number of COOH and OH groups [5]. Humic supplies are separated into humin, humic acid (HA), and fluorocarbon acid based on their solubility under acidic or alkaline circumstances in aqueous solutions [6]. The proportion of HA as a critical component of humic substances can increase with the microbial degradation of biomolecules and may form a significant portion (40–90%) of the dissolved organic matter (DOM) in almost all water sources [7]. HA has aliphatic and aromatic features, and its molecular weight ranges between 500 and 250,000 [8].

The negative charge of the humic material can lead to an increased transportation of different metals and elements such as bromine that consequently results in an increased toxicity and intensification of toxic byproducts generation [9]. There is an upward concern about the adverse effects of HA on living organisms due to the persistent nature and high tendency to adsorbing various contaminations, comprising pesticides and heavy metals [10].

Humic substances should be removed from water treatment systems in different ways: (a) Producing disinfection by-products (DBPs) such as trihalomethanes by reacting with chlorine in water purification; (b) Increasing the transportation of hydrophobic organic pollutants or heavy metals by joining to them; (c) Causing bacteria to grow in water distribution systems being as food sources; and (d) Creating unpleasant odor and taste in drinking water [11]. In general, the concentration of humic substances in natural water was reported in the range of 1.0 to 10 mg/L [12]. Humic acid has been known as one of the primary precursors of disinfection by-products, especially trihalomethanes (THM) and halo acetic acid (HAA), which have adverse health effects comprising the potential for carcinogenicity and undesirable effects on renal, hepatic, neurological, and genital/reproductive tissues [13].

Commonly, conventional methods for removal of humic substances include coagulation [14], membrane filtration [15], ion exchange [16], advanced oxidation process (AOP) [17], and adsorption [18].

The coagulation process produces a large amount of sludge and high operating costs. Ionic exchange reestablishes high amounts of salt and hummus. The membrane processes produce liquid waste and the humic substances tends to block the membrane, which limits the use of membranes [19]. Adsorption is an acceptable method due to the simplicity, low operational cost and capability in eliminating acid folia in water. As a consequence, many adsorbents including activated carbon [5], resin [20], chitosan [21], iron oxides [22], and various forms of nanographene [2], graphene oxide [23], and other adsorbents have been employed to remove these substances from aquatic systems. In case that the use of the above adsorbents is essential to remove large-scale humic acid (e.g., in a municipal water plant), the provision, preparation, and recovery of most of these adsorbents are not nearly cost-effective. Thus, it is necessary to find adsorbents with high abundance, and low cost and, then, focus shall be made to improve the efficiency of this type of adsorbent via various modification methods.

One of the cheapest and most abundant adsorbents that have received considerable attention by environmental researchers to remove various pollutants from aqueous solutions is pumice stone. Pumice stone as a natural stone is a silica glass with a color that varies from bright to dark gray. It has a specific surface area between 28 and 54 m2/g, high porosity (85%), structurally with irregular cavities, dry weight of 500 to 800 kg per m2, Mohs hardness of 5–6, and 60 to 75 percentage of silica [24].

Pumice stone as a natural adsorbent was utilized for the removal of various pollutants including heavy metals [24], multiple colors [25,26], phenols and their derivatives [27], fluoride, nitrate [28], and ammonium [29]. Nevertheless, few studies have been carried out on the use of this adsorbent in the removal of humic acid [30]. Thus, further research is needed to characterize the use of this adsorbent in removing humic substances from aquatic environments.

The present study aimed to scrutinize the efficiency of pumice modification with five different acids (acetic acid, hydrochloric acid, phosphoric acid, humic acid, and nitric acid) in removing humic acid from aqueous solutions. Accordingly, a new method was used in this study for pumice adsorbent modification by using five different acids (acetic acid, chloride, phosphoric acid, humic acid, and nitric acid) to compare the impact of these acids on the adsorbent efficacy and also, surveying the effects of these acids on pumice structure for the humic acid removal. Additionally, response surface methodology (RSM) was employed to investigate the role of influential parameters (pH, adsorbent dose, contact time, and initial concentration of HA) on the process of adsorbing humic acid and to develop the optimal conditions for the operation.

Section snippets

Chemicals, equipment and adsorbent characteristics

Raw Pumice was obtained from Qorveh region in Kurdistan province, Iran. All chemicals of analytical grade including, NaOH (CAS 1310-73-2), HCl (CAS. 7647-01-0), H2SO4 (CAS 7664-93-9), HNO3 (CAS 7697-37-2), H3PO4 (CAS. 7664-38-2) and CH3COOH (CAS.64–19-7) were purchased from Merck (Darmstadt, Germany). The working solution of humic acid was prepared by proper dilution of its original stock using double distilled water (DDW) according to Part 2.3. (Preparation and purification of humic acid (HA)

X-ray fluorescence (XRF) analysis

The X-ray fluorescence analysis was employed to distinguish the structure of the adsorbent and changes in its formation due to the modification with different acids. Table 4 displays the XRF results of the raw and modified pumice. XRF can be utilized to identify interactions between components of pumice and different acids used to modify it. In this interaction, three possible states can be observed: a) some materials would be physically dissolved in acid solution, b) some of them may react

Conclusion

In this research, the adsorption process of humic acid by the modified pumice with five different acids (acetic acid, hydrochloric, phosphoric acid, sulfuric acid, and nitric acid) and the raw pumice was studied. The removal efficiencies for the absorbents were as H2SO4-MP > HNO3-MP > H3PO4-MP > HCOOH-MP > HCl-MP > Raw-P. Additionally, by increasing the adsorbent dose and contact time, the HA removal efficiency by both the raw and modified adsorbents was increased; while the removal efficiency

Acknowledgment

This research was part of an MSc degree thesis in the environmental health engineering and was financially supported by the grants of Tehran University of Medical Sciences (TUMS), Tehran, Iran (code: 97-03-27-39639), and (code: 97-02-27-38186).

References (63)

  • S. Agarwal

    Rapid removal of noxious nickel (II) using novel γ-alumina nanoparticles and multiwalled carbon nanotubes: kinetic and isotherm studies

    J. Mol. Liq.

    (2016)
  • Z. Zaheer et al.

    Adsorption of methyl red on biogenic Ag@ Fe nanocomposite adsorbent: Isotherms, kinetics and mechanisms

    Journal of Molecular Liquids

    (2019)
  • M. Yousefi

    Performance of granular ferric hydroxide process for removal of humic acid substances from aqueous solution based on experimental design and response surface methodology

    MethodsX

    (2019)
  • G. Wang et al.

    Independent component analysis and its applications in signal processing for analytical chemistry

    TrAC Trends Anal. Chem.

    (2008)
  • J. Jaafari et al.

    Optimization of heavy metal biosorption onto freshwater algae (Chlorella coloniales) using response surface methodology (RSM)

    Chemosphere

    (2019)
  • O.B. Ayodele

    Effect of phosphoric acid treatment on kaolinite supported ferrioxalate catalyst for the degradation of amoxicillin in batch photo-Fenton process

    Appl. Clay Sci.

    (2013)
  • A.K. Panda

    Effect of sulphuric acid treatment on the physico-chemical characteristics of kaolin clay

    Colloids Surf. A Physicochem. Eng. Asp.

    (2010)
  • C.-C. Huang et al.

    Effect of surface acidic oxides of activated carbon on adsorption of ammonia

    J. Hazard. Mater.

    (2008)
  • G.K. Sarma et al.

    Adsorption of crystal violet on raw and acid-treated montmorillonite, K10, in aqueous suspension

    J. Environ. Manag.

    (2016)
  • M. Heydari

    Data for efficiency comparison of raw pumice and manganese-modified pumice for removal phenol from aqueous environments—application of response surface methodology

    Data in brief

    (2018)
  • A. Daifullah et al.

    A study of the factors affecting the removal of humic acid by activated carbon prepared from biomass material

    Colloids Surf. A Physicochem. Eng. Asp.

    (2004)
  • A. Sheikhmohammadi

    Application of graphene oxide modified with 8-hydroxyquinoline for the adsorption of Cr (VI) from wastewater: optimization, kinetic, thermodynamic and equilibrium studies

    J. Mol. Liq.

    (2017)
  • M. Auta et al.

    Optimized waste tea activated carbon for adsorption of Methylene Blue and Acid Blue 29 dyes using response surface methodology

    Chem. Eng. J.

    (2011)
  • J. Jaafari

    Adsorption of p-cresol on Al2O3 coated multi-walled carbon nanotubes: response surface methodology and isotherm study

    J. Ind. Eng. Chem.

    (2018)
  • Q. Tao

    Adsorption of humic acid to aminopropyl functionalized SBA-15

    Microporous Mesoporous Mater.

    (2010)
  • Y. Zheng et al.

    Fast removal of ammonium ion using a hydrogel optimized with response surface methodology

    Chem. Eng. J.

    (2011)
  • M. Malakootian et al.

    Assessing the performance of silicon nanoparticles in adsorption of humic acid in water

    Iranian Journal of Health and Environment

    (2014)
  • S. Jayalath

    Surface adsorption of Suwannee River humic acid on TiO2 nanoparticles: a study of pH and particle size

    Langmuir

    (2018)
  • E. Bazrafshan et al.

    Humic acid removal from aqueous environments by electrocoagulation process using iron electrodes

    Journal of Chemistry

    (2012)
  • A. Mahvi

    Reduction of humic substances in water by application of ultrasound waves and ultraviolet irradiation

    Iranian Journal of Environmental Health

    (2009)
  • T. Zhou

    Efficient separation of water-soluble humic acid using (3-Aminopropyl) triethoxysilane (APTES) for carbon resource recovery from wastewater

    ACS Sustain. Chem. Eng.

    (2018)
  • Cited by (47)

    • Comparison of the adsorption efficiency of cationic (Crystal Violet) and anionic (Congo Red) dyes on Valeriana officinalis roots: Isotherms, kinetics, thermodynamic studies, and error functions

      2022, Materials Chemistry and Physics
      Citation Excerpt :

      The adsorption capacity of cationic CV dye decreases from about 735.0 mg/g to 32.2 mg/g, while the adsorption capacity of anionic CR dye decreases from about 95.0 mg/g to 23.9 mg/g. The decrease in adsorption capacity with an increasing amount of adsorbent can be attributed to the overlapping or aggregation of adsorption sites, resulting in a decrease in the total removal surface available for dye molecules and an increase in diffusion path length [49,50]. The changes in adsorption percentage and capacity of cationic CV and anionic CR dyes depending on the initial concentration were given in Fig. 5b. Adsorption studies were performed at initial dye concentrations of 10, 20, 30, 40, and 50 mg/L, keeping other parameters constant.

    • Adsorptive removal of humic substances using cationic surfactant-modified nano pumice from water environment: Optimization, isotherm, kinetic and thermodynamic studies

      2022, Chemosphere
      Citation Excerpt :

      The result of experimental data from Freundlich model showed nF > 1 (2.75 and 8.41 for NP and HMNP, respectively). The 1/nF value for NP was 0.36 and for HMNP it was 0.118, with closer 1/n value to zero, the interactive impact of adsorbate and sorbent will become stronger, so HMNP showed the greater affinity to HA molecules (Derakhshan et al., 2013) (Soleimani et al., 2019). Temkin isotherm model is used for showing the effects of indirect adsorbent–adsorbate interaction on adsorption isotherms and Heat of adsorption (Derakhshan et al., 2013).

    View all citing articles on Scopus
    View full text