Papers by Keyword: Humic Acid (HA)

Abstract: Synthesis or humification of humic substances (HSs) is the second widely applied organic compound transformation process after photosynthesis. Peat decomposition process results in a production of a HSs which has a high demand in agriculture, forestry, and gardening areas. Addition of the KOH is good option for environmental protection and K⁺ belongs to the nitrogen, potassium and phosphorous (NKP) mineral component. A homogenization process in a customize for commerce, where peat treatment technology was improved with the help of the cavitation effect. This effect was provided with the help of the high-speed mixer-disperser (HSMD) developed at Riga Technical University. Mechanical cavitation causes relatively high energy shifts from mechanical movement of cavitation causing elements to the liquid medium which causes efficient destruction of particles inside a suspension. Values of the peat particle diameter at 50 % in the cumulative distribution before and after 1, 2, and 3 homogenization cycles were measured in the present study. The aim of the present study was to find the optimal conditions (KOH concentration, cavitation cycles and reaction temperature) to produce potassium humate (K-HSs) regarding sustainable regenerative approach aspects. Cavitation treatment of the tested peat particle diameter at 50 % in the cumulative distribution (d₅₀) from 267 down to 129 µm; the peak in the size range from 160 up to 409 µm completely disappears and significantly decreases the number of Dalton’s which causes the more efficient formation of fulvic acid caused by increased concentration of carbonyl and carboxyl groups as compared with the conventional homogenization method.

Abstract: Interfacial polymerization of a thin film composite (TFC) layer on top of a miroporous support membrane or other porous substrate is one of adequate method to form nanofiltration membrane in order to remove humic acid. Ultrafiltration (UF) polyethersulfone (PES) was used as membrane base support. Reaction occurred on the surface of membrane between two phase which are triethanolamine (TEOA) and trimesoyl chloride (TMC) as aqueous solution and organic solution respectively. Membrane that produced characterized by permeability, charged solutes rejection including salt solutions (NaCl and Na₂SO₄₎ and humic acid removal. Properties of membrane can be attributed with the changes of monomer concentration and reaction time. Pure water flux J_w for membranes calculated as a function of applied pressure to membrane ΔP. Thus, flux increased linearly with operating pressure is applied to membrane where meets Hagen-Poiseuille equation and gradient of every straight line give pure water permeability data. The variation of reaction time (15, 25 and 35 min) at 8% (w/v) monomer concentrations can affect the properties of the membrane produced and decreasing water permeabilities. The rejection order of the membrane changed from 0.001 M Na₂SO₄ > 0.1M Na₂SO₄> 0.001M NaCl > 0.1M NaCl. Humic acid removal resulted almost fully rejection showed that nanofiltration membrane is one of the best methods in water treatment technology.

Abstract: In the paper, the optimization of the coagulation process for Kaolin and humic acid removal using polymeric aluminum ferric sulfate (PAFS) was studied. In order to obtain the maximum turbidity and humic acid removal efficiency of Kaolin and humic acid simulated wastewater, the optimum coagulation conditions was investigated with the factors of mixing speed and time. Furthermore, mixing speed and time including parameters affecting the coagulation performance such as rapid mixing speed, rapid mixing time, slow mixing speed and slow mixing time using single factor and orthogonal array L9 (34) analysis were examined. The results showed that the optimum single factor of mixing speed and time indicated rapid mixing speed of 350 rpm, rapid mixing time of 1.0 min, slow mixing speed of 60 rpm and slow mixing time of 20 min. Then the orthogonal optimization experiment of mixing speed and time indicated maximum HA removal efficiency was 97.5% at rapid mixing speed of 350 rpm, rapid mixing time of 1.25 min, slow mixing speed of 60 rpm, and slow mixing time of 20 min.

Abstract: Results of investigation of naphthalene interaction with humic acids of high-moor peat and their fractions are presented in the article. The elemental and structural-group compositions of humic acids of high-moor peat and of their fractions are determined, average values of their molecular masses are found, and their spectral and luminescent properties are investigated. Numerical values of constants of naphthalene interaction with humic acids and their fractions are calculated, and the polarity of naphthalene microenvironment in solutions of humic acids is estimated. The results of investigations suggest that the maximum affinity of naphthalene is observed to the fraction of hematomelanic acids and that the naphthalene microenvironment in solutions of the given fraction is polar.

Abstract: Humic substances are the major components of soil, peat and brown coal. They can be fractionating into fulvic acids (FA), brown humic acids (BHA) and gray humic acids (GHA). In this work we investigated the influence of mechanochemical modifications on structural composition of HAs main fractions using the methods of IR and ¹H MRS spectroscopy. The IR spectroscopy results has shown that HA has different chemical composition in comparison with GHA and BHA. Potentiometric titration showed that mechanoactivation (MA) with thiourea increases the amount of oxygen-containing groups up to 2.5. For the first time we studied the impact of modifying agent of thiourea on the structural composition and acid-base properties of HAs major fractions - GHA and BHA during the mechanoactivation process.

Abstract: In this study, three kinds of natural clay minerals (kaolin clay, montmorillonite and diatomaceous earth) were used to treat the raw water containing humic acid (HA) by adsorption/sedimentation. The results indicated that natural kaolin clay had no obvious effect on removing HA in water. Using chitosan to modify montmorillonite and diatomaceous earth, the removal effect of the modified diatomaceous earth for HA was better than modified montmorillonite, and the optimal ratio between chitosan and diatomaceous earth was 1:30. Compared with natural diatomaceous earth, the modified clay had better adsorption property for HA at the same dosage. Using modified diatomaceous earth, the maximal removing rates for TOC and turbidity could respectively reach 85.9% and 64.6% with 60 mg/L dosage and 50 min.

Abstract: Biofilm main constituents of the humic acid and synthetic ferrihydrite were used as sorbent on the Wuhai sediment of Yellow River, comparative analysis the Wuhai section sediment of the Yellow River and after doping humic acid and ferrihydrite of Cd²⁺ adsorption characteristics. Discusses the adsorption time, various initial concentrations on Cd²⁺ adsorption onto sediments from Wuhai of Yellow River.The adsorption isotherms and adsorption kinetics were fitted and distribution coefficients were calculated. The results illustrated that the adsorption processes of sediments with different proportions of biofilm main constituents to Cd²⁺ were consistent with Langmuir adsorption isotherm curves (R²≧0.99,p≦0.02,n=7); Doping of humic acid and ferrihydrite on sediment, the distribution coefficients of Cd²⁺ were 6.2959 and 2.711, which were higher than the original (0.8626).

Abstract: Ultrafiltration test was carried out to simulate the pollution performance of humic acid (HA) solution. The HA adsorption properties on membrane surface was studied by static adsorption experiment. The influences of HA concentration on adsorption characteristics were taken into account. And Freundlich isotherm model was used to evaluate of adsorption isotherms.

Abstract: Composite magnetic microspheres of chitosan (CTS) and quaternary ammonium chitosan derivative (HTCC) were prepared by inverse suspension method. Tripolyphosphate (TPP) and glutaraldehyde were used successively to co-crosslink the microsphere matrix. The morphology was analyzed using optical microscopy and scanning electron microscopy (SEM), while the chemical composition was characterized using Fourier transform infrared spectroscopy (FTIR). The adsorption of humic acid (HA) by the composite magnetic microspheres (CHMMs) was investigated in terms of adsorption capacity and kinetics in order to optimize preparation conditions. Both CTS/HTCC mass ratio and crosslinker dosage greatly affected the properties of the microspheres. A batch of CHMMs was prepared when the mass ratio of CTS and HTCC was 1:1 and TPP and glutaraldehyde were17% and 30% of total mass of CTS and HTCC, respectively. These CHMMs were between 150 and 800 μm. 85% HA was able to be removed in 60 min using this proposed absorbent. It was fast and efficient for HA removal from aqueous solution.

Abstract: In this study, the formation of trihalomethanes (THMs) during chlorination or chloramination after different pretreatments including single nanoTiO₂ adsorption, single UV treatment or the combination of UV/TiO₂ under the same pH, TiO₂ dose and humic acid concentrations were evaluated. Effect of different pretreatments on the reduction of non-purgeable organic carbon (NPOC) and UV₂₅₄ before the disinfection was investigated. The result showed that single UV and single TiO₂ adsorption to reduce NPOC and UV₂₅₄ values is negligible, and the combination of UV/TiO₂ removed 45% of NPOC and 72% of UV₂₅₄ after 480min reaction. For the formation of the THMs during the followed chlorination, it was found that the combination pretreatment of UV/TiO₂ resulted in a parabolic trend for the formation of the THMs while single UV pretreatment increased steadily and single TiO₂ pretreatment kept stable. Chlorination generated higher concentrations of total THMs than chloramination. The total THMs produced by chloramination only represented <5% of that of chlorination.