Initial Humic Acid Concentration Research Articles

Enhanced Removal of Dissolved Effluent Organic Matter in Wastewater Using Lignin-Based Biochar Supported Fe–Cu Bimetallic Oxide Catalyst

The effluent discharged from wastewater treatment facilities frequently enters the ocean, posing a considerable threat to the health of marine life and humans. In this paper, an alkali lignin-based biochar-loaded modified Fe–Cu catalyst (FeCu@BC) was prepared to remove soluble microbial products (SMP) from secondary effluent as disinfection by-products precursors at ambient temperature and pressure. The humic acid (HA) was taken as the representative substance of SMP. The results showed that the maximum removal efficiency of HA reached 93.2% when the FeCu@BC dosage, pH, initial HA concentration, and dissolved oxygen concentration were 5.0 g/L, 7, 100 mg/L, and 1.75 mg/L, respectively. After three cycles, the removal efficiency of HA could be maintained at more than 70%. The quenching experiments and electron spin resonance (EPR) results showed that •OH and 1O2 were involved in the degradation of HA in the FeCu@BC catalyst reaction system, with 1O2 playing a dominant role. Theoretical calculations confirmed that •OH and 1O2 were more prone to attack the C=O bond of the side chain of HA. After processing by the FeCu@BC catalyst, the yield of chlorinated disinfection by-products from secondary effluent had decreased in an obvious manner. This study provides a new solution to efficiently solve the problem of chlorinated disinfection by-products from HA.

Binding capacity and co-migration potential of Pb(II), Cu(II), and Cd(II) on colloids in road runoff

ABSTRACT To evaluate the co-migration potential between heavy metal ions and road runoff colloids, the influence of contact time, temperature, initial concentration of metal ions, pH, humic acid (HA), and polymetallic coexistence on the binding capacity of heavy metals onto runoff colloids were investigated. The adsorption of heavy metals by runoff colloids was extremely rapid, approximately 80% of the equilibrium adsorption capacity was achieved in the first 30 min. The binding capacity exhibited an increasing trend with the initial concentration of metal ions increasing, and the maximum adsorption capacities of Pb(II), Cu(II), and Cd(II) achieved 159.13, 56.06, and 78.35 mg/g at 298 K, respectively. The adsorption capacity of Cu(II) and Cd(II) by runoff colloids increased with temperature increasing, while it displayed a converse trend for Pb(II). Neutral pH facilitated the combination of metal ions and runoff colloids. The presence of humic acid increased the binding capacity of Pb(II), Cu(II), and Cd(II) onto runoff colloids by 72.19, 63.31, and 13.83mg/g, respectively. Compared to the monometallic systems, the binding capacity of Pb(II), Cu(II), and Cd(II) by runoff colloids decreased by 18.44%, 22.35%, and 56.06% in polymetallic systems, respectively. Pb(II) bounded with colloids in the road runoff should be controlled preferentially to avoid their migrations to aquatic environments.

Evaluation of the efficiency of the TiO2 /UV nano-photocatalytic process in the removal of humic and fulvic acids from aqueous solutions

Background: Removing natural organic substances from drinking water sources is necessary to prevent the formation of toxic and carcinogenic disinfection by-products (DBPs). The nano-photocatalytic oxidation process to remove these substances is easier, faster, cheaper, and more efficient than other methods. Methods: This study investigated the efficiency of the TiO2 /UV nano-photocatalytic process in removing humic acid (HA) and fulvic acid (FA) from aqueous solutions. Batch tests were performed to investigate the effect of various parameters such as contact time (15, 30, 45, 60, and 75 minutes), initial pH (4, 7, and 9), initial HA and FA concentration (0.5, 1, 2, 5, and 7 mg/L-1), TiO2 dose (5, 10, 15 and 20 mg/L-1), and different UV irradiation (8 W and 16 W) for the removal of HA and FA from aqueous solutions using TiO2 /UV at room temperature (20±3 °C). The equilibrium adsorption data and the standard parameters were evaluated. Data were analyzed using SPSS version 25. Results: The efficiency of this process in optimal conditions (pH: 4, anatase TiO2 : 10 mg/L-1, irradiation time: 60 min, UV=16 W) for removing humic and fulvic (initial HA concentration: 2 mg/L-1 and initial FA concentration: 5 mg/L-1) was 89% and 92%, respectively. The analysis of the experimental isotherm data showed that in the adsorption process of HA and FA on TiO2 /UV, the Langmuir isotherm and the first-order reaction had the best fit with the experimental data. Conclusion: TiO2 /UV nano-photocatalytic process is suitable for the photo-degradation and removal of HA and FA in aqueous solutions.

Investigating Humic Acid Adsorption from Aqueous Solution using UiO-66 Functionalized with Amine Group

Background: Natural Organic Matters (NOMs) are pollutants that exist in many drinking water resources, cause many problems in drinking water treatment processes, and have adverse effects on human health. For this reason, these substances must be removed from drinking water via a proper method. Metal Organic Frameworks (MOFs) are novel adsorbents that have been widely considered in recent years. In this study, Uio-66 functionalized with NH2 was synthesized and applied for humic acid adsorption (as a natural organic matter) removal from water. Materials and Methods: The present study was conducted in a batch reactor and on a laboratory scale. Firstly, the characteristics of the synthesized adsorbent were investigated. Then, the effect of different parameters such as pH, adsorbent dosage, and initial concentration of humic acid on adsorption process was also investigated. Additionally, isotherms and kinetics of humic acid adsorption on Uio-66-NH2 adsorbent were determined. The data analysis and isotherms comparisons were conducted using linear regression and determination coefficient. Results: In this study, the analysis confirmed the structure and properties of the fabricated nanoparticles. The adsorbent surface area was 673.4 m2/g. The results also showed that the optimal pH for adsorption of humic acid was in the range of 5 to 7, the optimal dose of adsorbent was 0.8 g/L, and the maximum adsorption of humic acid was 2.2 mg/g of adsorbent. Conclusion: Based on the findings of the present research, humic acid adsorption isotherm on the adsorbent was in accordance with the Langmuir isotherm model and its adsorption kinetics followed the pseudo-second-order kinetic model. The current study revealed that by optimization of the condition, the adsorbent can be used for organic matter removal.

Competitive Removal of Antimony and Humic Acid by Ferric Chloride: Optimization of Coagulation Process Using Response Surface Methodology

The co-contamination of aquatic systems with antimony (Sb) and humic acid (HA) is a global concern due to their potential risks to human health and environment. In this research, three-level-three-variable Box–Behnken design (BBD) was investigated for simultaneous Sb(III) and total organic carbon (TOC) removal responses from groundwater by use of ferric chloride (FC) as a coagulant. This study focuses on three operating variables, including initial Sb(III) concentration (100, 550, and 1000 μg/L), HA concentration (2, 6, and 10 mgC/L) and FC dosages (20, 60, and 100 mg/L). The proposed quadratic model presented good correlation with experimental values having R2 and adjusted R2 values of response variables (Sb(III): 0.9981 and 0.9956) and (TOC: 0.9935 and 0.9851), respectively. The most pronounced influence of FC dosage was observed in the removal responses of TOC and Sb(III). Interestingly, the model revealed that a high level of FC dosage had the same TOC removal potential regardless of increasing HA concentration. The statistical model for both Sb(III) and TOC responses was used to optimize the experimental conditions. Moreover, the experimental results were successfully validated with predicted values having high accuracy. The sludge volume produced for studied variables followed the decreasing order as FC dosage > HA concentration > Sb(III) concentration. Under optimum conditions, 0.45 mL/L sludge volume was produced in the treatment of ground water in Nawabshah. In general, the results of the current study may provide some insights into the predictability of simultaneous removal performance of Sb species and organic substances from groundwater.

Preparation of entrapment-based microcolumns for analysis of drug-humic acid interactions by high-performance affinity chromatography

Reversible interactions between drugs and humic acid in water can be an important factor in determining the bioavailability and effects of these pharmaceuticals as micropollutants in the environment. In this study, microcolumns containing entrapped humic acid were used in high-performance affinity chromatography (HPAC) to examine the binding of this agent with the drugs tetracycline, carbamazepine, ciprofloxacin, and norfloxacin. Parameters that were varied to optimize the entrapment of humic acid within HPLC-grade porous silica included the starting concentration of humic acid, the mass ratio of humic acid vs silica, and the method of mixing the reagents with the support for the entrapment process. The highest retention for the tested drugs was obtained when using supports that were prepared using an initial humic acid concentration of 80 mg mL−1 and a humic acid vs silica mass ratio of 600 mg per g silica, along with preincubation of the humic acid with hydrazide-activated silica before the addition of a capping agent (i.e., oxidized glycogen). Characterization of the humic acid support was also carried out by means of TGA, FTIR, SEM, and energy-dispersive X-ray spectroscopy. The binding constants measured by HPAC for the given drugs with entrapped Aldrich humic acid gave good agreement with values reported in the literature under similar pH and temperature conditions for this and other forms of humic acid. Besides providing valuable data on the binding strength of various drugs with humic acid, this work illustrates how HPAC may be used as an analytical tool for screening and characterizing the interactions of drugs and man-made contaminants with humic acid or related binding agents in water and the environment.

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

In this study, nano pumice (NP) and a cationic surfactant (hexadecyltrimethylammonium-chloride (HDTMA.Cl)) treated nano pumice (HMNP) were used for humic acid (HA) adsorption from an aqueous solution. The adsorption process was modeled and optimized using Response surface methodology-central composite design (RSM-CCD) and Artificial neural networks- Genetic algorithm (ANN-GA). The results show that the ANN model outperforms the RSM-CCD model in terms of response prediction. Optimization results based on the RSM-CCD approach proposed pH 3, adsorbent dose 3 g L−1, reaction time 60 min, and initial HA concentration 5 mg L−1 as optimal points of the variables, to reach the maximum adsorption efficiency of 100% and 65.4% by HMNP and NP adsorbents. The maximal adsorption capacity of NP was 1.21 mg g−1, while that of HMNP was 27.34 mg g−1. The optimal points of process parameters by the ANN-GA method are in accordance with the values suggested by the RSM-CCD method. In isotherm studies, Langmuir model was found to be the best-fitted model for both adsorbent with R2 = 0.97 for NP and 0.992 for HMNP, and also among three different kinetic models which were assessed, Pseudo-second-order model with R2 = 0.9989 for HMNP and R2 = 0.9957 for NP were the best-fitted models for HA removal. Thermodynamic studies indicated that the HA adsorption process by both of the adsorbents is endothermic and the nature of HMNP was found spontaneous while for NP was non-spontaneous. The value of ΔH for both adsorbents was in the range of 34–36.8 kJ mol−1 so the process is clarified as chemical–physical adsorption. The reusability test revealed that the adsorption effectiveness of HMNP drops from 100% to 82.4% after 10 consecutive recycles. The influence of interfacing anions indicated that the adsorption efficiency drops from 100% to 95.4% when the anions were added to the reaction solution.

Evaluation of a Nanohybrid Membrane (PSF/ZnO) Efficiency in Natural Organic Matter Removal From Water

Background: Natural organic matter (NOM) in drinking water sources has always been regarded as a precursor for the formation of trihalomethanes (THMs), haloacetic acids (HAAs), and carcinogenic properties. This study aimed to fabricate and characterize a nanohybrid ultrafiltration membrane (PSF/ZnO) to evaluate its efficiency in NOM removal from water. Methods: Nanohybrid membranes with ratios of 0, 1, 2, 3 and 4% w/w of ZnO nanoparticles (NPs) were fabricated using the phase inversion method and characterized by the contact angle, AFM, FTIR, and SEM analyses. In this study, the effects of initial humic acid (HA) concentration, operating pressure, pH, and filtration time were examined on the HA removal efficiency and pure water flux through the membrane. Results: The results showed that addition of the ZnO NPs to the PSF membrane reduced the contact angle on the PSF/ZnO nanohybrid membrane’s surface. According to FE-SEM images, increasing the ZnO concentration changed the porous structure of the membranes from a spongy, teardrop shape to a finger-like channel structure. The FTIR analysis revealed an increase in the hydrophilicity of the membrane due to the presence of hydroxyl functional groups in ZnO. AFM images indicated an increase in the surface roughness of nanoparticle-containing membranes. It was found that an increase in the concentration of the ZnO NPs (0-4% w/w) increased HA removal efficiency (43.63-83.4%). Conclusion: This study demonstrated that the use of the PSF/ZnO nanohybrid membranes increased HA removal efficiency and pure water flux passing through the membrane.

Humic Acid Removal in Water via UV Activated Sodium Perborate Process

Humic acid (HA) has complex molecular structure and is capable of adsorption, ion exchange, and chelation with organic and inorganic pollutants in water bodies, worsening water quality and jeopardizing human health and ecological environment. How to effectively remove HA from water is one of the research focuses of this paper. In this study, the UV-activated sodium perborate (SPB) synergistic system (UV/SPB) was established to eliminate HA in water. The effects of initial HA concentration, SPB dose, and initial pH value on the HA elimination were determined, and the main mechanisms of the synergy and HA degradation were explored. The outcomes show that the HA elimination ratio by the sole UV and only SPB system were only 0.5% and 1.5%, respectively. The HA removal of UV/SPB reached 88.8%, which can remove HA more effectively than other systems. Free radical masking experiment proved that hydroxyl radical produced by SPB activation is the main active substance for HA removal. The results of UV-vis absorption spectrum, absorbance ratio, specific UV absorbance, and excitation–emission matrix spectroscopy verified that the UV/SPB system can effectively decompose and mineralize HA.

Ti4O7 reactive electrochemical membrane for humic acid removal: Insights of electrosorption and electrooxidation

Electrochemical advanced oxidation processes (EAOPs) are regarded as a promising technology for the treatment of landfill leachate containing high concentrations of humic acid (HA). Herein, a Ti4O7-based porous reactive electrochemical membrane (REM) system was developed and explored for the rapid and effective removal of HA. The relationship between the electrolyte medium (Na2SO4 or NaCl) and the adsorption/oxidation capacity of the REM system for HA removal was comparatively studied under different ionic strengths. An unprecedented trade-off phenomenon was revealed between the electrosorption and electrooxidation induced by chloride ions. On one hand, the pH value of the aqueous solution increased due to the loss of Cl− (NaCl → NaOH) during the electrolysis process in the NaCl medium, which weakened the electrosorption ability of REM on HA and further led to deterioration of the effluent quality. On the other hand, the introduction of chlorine significantly strengthened the mineralization performance of HA adsorbed on the anode surface because the anode enabled the oxidation of Cl− into powerful active chlorine species. Current density, membrane permeability, solution pH, and initial HA concentration were identified as the key parameters affecting the overall degradation performance. The active radicals (Cl and OH) involved in the REM system were systematically studied and generation pathways were proposed accordingly. This study facilitates understanding of the surface catalytic behavior of the Ti4O7 REM in a NaCl medium and confirms that this is a powerful and efficient technology for HA removal.

Exploring the synergism of sunlight and electrooxidation on persulfate activation for efficient degradation of bisphenol S: Performance, Pathway, and mechanism

Sulfate radical-based advanced oxidation processes had been widely applied in the water treatment. In this study, a novel solar-assisted electrooxidation process (SEOP) to activate peroxymonosulfate (PMS) or peroxydisulfate (PDS) was conducted for the degradation of bisphenol S (BPS). The SEOP with persulfate (PS) demonstrated its synergistic effect for BPS degradation, compared with the electrooxidation/PS and the solar process. The hydroxyl radical, sulfate radical (SO4·-), and singlet oxygen were regarded as primary active species in BPS degradation in SEOP with PS. The transition structure complex (persulfate*) on the anode promoted the efficiency of BPS degradation via the non-radical mechanism. The activation of PMS and PDS in SEOP was dominated through radical and non-radical mechanism, respectively. To effectively supplement experimental work with quantum chemical calculation, density function theory (DFT) showed that the active sites mainly focused on the phenol ring of BPS. The energy barrier calculation indicated that BPS was more susceptible to be attacked by SO4·- through electron transfer. BPS was mainly degraded by ring-opening, substitution, addition, C–C bond breaking, and decarboxylation reactions. Furthermore, the effective decrease in bio-toxicity of BPS intermediates in SEOP with PS was predicted. Experiments under various current densities, initial concentration of PS, electrolyte, and humic acid suggested the feasibility of SEOP with PS. BPS was degraded with lower energy consumption (0.18 kWh·m−3·order−1) in SEOP with PMS than that in SEOP with PDS (0.30 kWh·m−3·order−1) and without PS (0.38 kWh·m−3 order−1), respectively. The SEOP with PS poses the feasible, convenient, and economic potential for the degradation of refractory pollutants.

Natural organic matter removal by electrospun nanofiber membranes coated with heated aluminum oxide particles

The removal of natural organic matter (NOM) from water was studied using polyacrylonitrile (PAN) electrospun nanofibrous membrane (ENM) coated with HAOPs (heated aluminum oxide particles). The removal efficiencies of virgin PAN and HAOP-coated PAN were examined and the suitability of PAN as a support material for HAOPs was studied.The membranes were characterized with Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscope and energy dispersive X-ray spectrometer (SEM-EDS) as well as X-ray photoelectron spectroscopy (XPS). Several analytical techniques were applied to both the feed and the permeate to assess the effectiveness of NOM removal.In filtration of lake water, HAOPs efficiency in NOM removal was 56% measured by UV254 absorbance, but when it comes to virgin PAN membrane the removal efficiency was only 13%. In case of filtration of NOM's high molecular weight component, such as humic acid (HA), the rejection rate of HA was maintained above 97% of aromatic compounds of NOM, and above 43% of total organic carbon (TOC).Additionally, HA adsorption by HAOPs were fitted to isotherm models such as Langmuir and Freundlich models. The results showed that Langmuir model could fit the data better than Freundlich model. The kinetics of HA adsorption by HAOPs were also fitted to the pseudo-first order and pseudo-second order and for the initial HA concentration of 19.9 mg/L the pseudo-first order equation fitted the experimental data better with correlation coefficient of R2 = 0.8336.The results demonstrate that PAN ENM filtration has the potential to be employed as a pretreatment in water treatment and HAOP-coated PAN ENM can significantly enhance the removal of NOM.

Enhanced photo-catalytic degradation of natural organic matters (NOMs) with a novel fibrous silica-copper sulfide nanocomposite (KCC1-CuS)

The present study aims to test the degradation ability of KCC-1/CuS nanocomposite as a new photocatalyst for Humic acid (HA) degradation. The degradation process was accomplished using a photocatalytic reaction under irradiation by UV light A facile method applied for catalyst synthesis in different condition, and it was structurally and morphologically characterized, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray Spectroscopy (EDX) and Thermo Gravimetric Analysis (TGA) which showed successful synthesis of KCC-1/CuS nanocomposite.The degradation process was examined as a function of pH (3–11), catalyst dose (0.005-0.1 g/L), contact time (0–90 min) and initial HA concentration (2–15 mg/L) under UV radiation. The results demonstrated that maximum degradation of HA was 89.5% in optimized environmental conditions including pH: 3, nanocomposite dosage: 0.1 g/L, contact time: up to 90 min and initial HA concentration: 2 mg/L.

Improving the ZnO-photocatalytic degradation of humic acid using powdered residuals from water purification plant

Abstract Alum residuals were collected from a water treatment plant and used for improving the photocatalytic degradation of humic acid (HA) by combinations of zinc oxide (ZnO) and powdered residuals from a water purification plant (PRWPP). The influence of operating conditions such as initial humic acid concentration, pH, irradiation time, PRWPP to ZnO ratio, catalyst dose, and light illuminance have been investigated. The optimum PRWPP to ZnO ratio was 10:90. Using the prepared composites instead of bare ZnO raised the HA removal efficiency from 85.5% to 97.8%, and from 38% to 48.1% at catalyst doses of 1.2 g/l and 0.4 g/l, respectively. Moreover, it reduced energy consumption from 210.4 to 166.2 Wh per mg of HA. An artificial neural network model (ANN) was developed to predict the removal efficiency under different operating conditions. The optimum ANN structure yielded a coefficient of determination (R2 = 0.993). A modified Langmuir-Hinshelwood pseudo-first-order model was used for describing the degradation kinetics at different initial concentrations of HA.

Investigating the role of the morphology of the Zn-Al LDH on the adsorption of humic acid from aqueous solutions.

Flake Zn-Al layered double hydroxides (FLDHs) and microspheres of LDH (MLDHs) were fabricated with a simple hydrothermal method to investigate the role of the morphology of Zn-Al LDH for humic acid (HA) adsorption from synthetic solutions and natural water. The effect of process variables, i.e. contact time, initial concentration of HA, pH, and competitive ions on the adsorption was investigated. HA removal mechanism was also studied. The two adsorbents exhibited different adsorption behaviors for HA in the presence and absence of background ions, which may be highly correlated with the various adsorption mechanisms involved. Comparison of the HA removal capacity of these two adsorbents implies the superior adsorption capability of FLDH for removal of HA from synthetic solutions (9.5 mg/g), while the adsorption capacity of MLDH was higher for natural organic matters present in natural water samples containing co-existing ions (8.9 mg/g). The pseudo-second-order kinetics model and Longmuir isotherm model could adequately interpret the HA adsorption process for the studied adsorbents. Both LDHs exhibited good regeneration and recycling abilities.

Ultrasonic Assisted and Neural Network Model for Adsorption of of humic acid (HAs) by Synthesised CM-β-CD-Fe3O4NPs from Aqueous Solutions

ABSTRACT In the present study, the applicability of CM-β-CD-Fe3O4NPs synthesis for eliminating humic acid rapidly from aqueous solutions. Identical techniques including BET, FT-IR, XRD and SEM have been utilised to characterise this novel material. The investigation showed the applicability of CM-β-CD-Fe3O4NPs as an available, suitable and low-cost adsorbent for the proper deletion of humic acid from aqueous media. Also, the impacts of variables including initial humic acid (HA) concentration (X1), pH (X2), adsorbent dosage (X3) and sonication time (X4) came under scrutiny using central composite design (CCD) under response surface methodology (RSM). The experiments have been designed utilising response surface methodology. In this current article, the values of 12 mg·L−1, 0.03 g, 7.0, 4.0 min were considered as the ideal values for humic acid (HA) concentration, adsorbent mass, pH value and contact time, respectively. The kinetics and isotherm studies proved the appropriateness of the second-order and Langmuir models for the kinetics and isotherm of the adsorption of humic acids (HAs) on the adsorbent. The adsorbent was proved to be recyclable more than once. Since almost 99.5% of humic acids (HAs) were deleted with ideal adsorption capacities of 105 mg·g−1 for humic acids (HAs). The use of artificial neural network model in predicting data with Levenberg–Marquardt algorithm, purelin or a linear transfer function at the output layer and tansig or a tangent sigmoid transfer function in the hidden layer with five neurons was helpful for deletion of humic acid (HAs), MSE (mean square error) of 0.33 for humic acid (HA) removal by CM-β-CD-Fe3O4NPs. The overall results confirmed that CM-β-CD-Fe3O4NPs could be a promising adsorbent material for humic acid (HA) removal from aqueous solutions.

Phytoremediation of Boron using Lemna minor from Synthetic Aqueous Solutions and Real Geothermal Water

In this study, phytoremediation performance of Lemna minor L. on boron removal from synthetic solution and real geothermal water was evaluated. Effects of initial boron concentration, initial pH, water height in cell, and initial humic acid concentration were investigated. The maximum removal efficiency was achieved as 96.7 % with the experimental run with 5 mg L-1 initial boron concentration, pH 8, and 1.5 cm water depth. Increasing the initial boron concentration from 5 to 30 mg L-1 resulted in a drastic decrease in removal efficiency to 36.6 %, due to the toxic effect of high boron content, which was clearly observed from deterioration of plant’s color and structure. SEM, FTIR, and mass balance analyses revealed that the boron removal mechanism was mainly biosorption. Geothermal water experiments indicated L. minor’s applicability with 59.5% removal efficiency, proving high potential in being used for post-treatment of geothermal waters with high boron content.

Experimental study on advanced treatment of landfill leachate by ultraviolet catalytic persulfate

Landfill leachate is characterized by complex composition and difficult degradation. In this paper, we compared the effects of advanced treatment of ultraviolet (UV) system, persulfate (PS) system and ultraviolet/persulfate (UV/PS) system on landfill leachate. The results showed that the UV/PS system had the best removal efficiency. When the initial concentration of humic acid was 200 mg/L, the dosing of PS was 25 mmol/L, and the initial pH was 4, the maximum removal rates of UV 254 and TOC were 89.62% and 76.17%. Namely, the value of SUVA 254 decreased to 7.6603 L/(m ⋅ mg). It follows that the UV/PS system is effective in the removal of humic acid in the landfill leachate. In addition, this paper investigated the effects of temperature, initial pH and dosing ratio of chemicals on the treatment of leachate by UV/PS system. It was found that the optimal process conditions were 35 °C, pH = 4, dosing ratio = 2, and 24 h of operation. Under these conditions, the maximum removal rates of COD and TOC were 82.64% and 66.69%. The removal capacity of the system was in accordance with the pseudo-second-order kinetic equation. Therefore, this paper can provide a reference for the advanced treatment of landfill leachate. • An advanced oxidation technology for the removal of landfill leachate after biochemical treatment was presented. • Humic acid was used as a model for organic matter. The value of SUVA 254 decreased to 7.660315 L/ (m ⋅ mg) under the optimum conditions. • Under the optimal conditions, the removal rates of COD and TOC of landfill leachate after biochemical treatment reached 82.64% and 66.69%. • SR-AOPs are more efficient, economical and widely applicable compared to other technologies for deep treatment of landfill leachate.

Low-pressure UV-initiated synthesis of cationic starch-based flocculant with high flocculation performance

A kind of starch-based flocculant (starch-graft-poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride], denoted St-g-PDMC-LPUV) has been synthesized by low-pressure ultraviolet initiation and was employed to remove humic acid (HA) for water purification. The physicochemical characteristics of starch and St-g-PDMC-LPUV were characterized by FT-IR, 1H NMR, XRD, TGA, SEM and BET to confirmed the successful grafting DMC onto starch. Effects of flocculant dosage, pH, the adding amount of Fe3O4, initial HA concentration and stirring speed were investigated systematically. The prepared St-g-PDMC-LPUV flocculant with non-toxic, biodegradability and environmental friendliness exhibited effective performance for removing HA from water in a wide pH range (5–10). The flocculation mechanism was attributed to the effective collision between function groups of the St-g-PDMC-LPUV flocculant and HA by charge neutralization, adsorption, bridging and patching.

Photocatalytic degradation of humic acid using a novel visible-light active α-Fe2O3/NiS2 composite photocatalyst

The effects of α-Fe2O3/NiS2 composite for the humic acid removal were systematically studied and compared with the synthesized α-Fe2O3 and NiS2. The obtained mesoporous composite has a stacked plate-like surface, active at a visible light region with a bandgap of 2.49 eV, and has a lower rate of recombination compared to the α-Fe2O3 but higher than the NiS2. The highest humic acid removal (93.7%) was achieved by the α-Fe2O3/NiS2 composite followed by the α-Fe2O3 (88.7%) and NiS2 (86.4%) at optimum conditions of 0.1 g L−1 catalyst loading, pH 5, and 30 mg L−1 initial humic acid concentration. The mineralization achieved 96.8% and the catalyst was stable up to the fourth cycle. These encouraging results were due to the better adsorption capacity of the composite, being active in visible light, and quenching of the photoluminescence that led to effective separation of subsequent reduction in the rate of recombination of the charged carriers.