Optimization of flocculation conditions for the separation of TiO2 particles in coagulation-photocatalysis hybrid water treatment

TiO₂ mediated photocatalysis can decompose organic micropollutants (e.g., 1,4-dioxane) in water, but the removal of used TiO₂ particles is challenging. Although retrofitting enhances the particle separation efficiency, optimizing a coagulation/flocculation process should be most suitable for existing treatment plants. Therefore, the present study investigated the separation characteristics of TiO₂ particles added to drinking water treatment processes along with a polyaluminum coagulant. TiO₂ photocatalysts were able to achieve significant degradation of 1,4-dioxane (∼100% within 50 min) as well as dissolved organic matter (∼75% within 150 min) at a TiO₂ dose of 1.0 g/L under UV irradiation. Although the TiO₂ particle separation efficiency was sensitive to G values, maximal removal occurred at a G value of <34 s⁻¹ with a coagulant concentration of >8 mg/L as Al₂O₃. Sand filters had the capability to remove residual turbid materials and thus, the turbidity of the final product water dropped to as low as 0.1 NTU when the coagulation/flocculation process was preceded. The final effluent quality was comparable to that of a 0.45-μm membrane filter. The post separation of the TiO₂ photocatalysts dispersed for emergency water treatment to degrade 1,4-dixoane was successfully achieved with an optimal coagulant dose, proper flocculation, and sand filtration.     

PDM复合混凝剂用于低温低浊水源水处理的研究——低浊度宁波姚江水处理

该文报道了用特征黏度系列化的有机阳离子高分子聚二甲基二烯丙基氯化铵(PDM)与无机混凝剂复合物对宁波低浊度姚江水的脱浊处理研究过程。通过混凝烧杯实验,考察了无机混凝剂的种类及其与PDM的复合配比对低浊度姚江水脱浊效果的影响。结果表明,对低浊度姚江水,要达到1.0~1.2 NTU的沉淀出水余浊,硫酸铝(AS)需5 mg/L左右的投加量,聚合硫酸铁(PFS)需8 mg/L左右的投加量,而聚合氯化铝(PAC)的投加量在10 mg/L左右;PDM对无机混凝剂强化混凝脱浊效果明显,无机混凝剂与PDM的复合配比越低,复合混凝剂混凝脱浊效果越好,在达到水厂沉淀出水浊度标准的前提下,AS/PDM复合药剂能比单独使用AS减少20%AS投加量;PFS/PDM复合药剂能比单独使用PFS减少30%~40%PFS投加量;PAC/PDM复合药剂能比单独使用PAC减少30%~50%PAC投加量。     

低温低浊河网水的有机高分子助凝处理研究

用不同特征黏度的聚二甲基二烯丙基氯化铵(PDM)与聚合氯化铝(PAC)、两种市售无机复合聚铝分别复合,用以改进无机混凝剂对低温低浊微污染河网水的混凝脱浊效果。考察了无机混凝剂的种类及其与PDM的复合配比对低温低浊微污染河网水脱浊效果的影响。结果表明,对温度为7～10℃,浊度为4.5～8NTU的低温低浊河网水,在与实际生产相近的混凝搅拌强度下,要达到2NTU左右的出水余浊标准,PAC、复合聚铝1、复合聚铝2分别需4.0、3.5、2.8mg/L的投加量。而用特征黏度分别为0.52、1.47、2.46 dL/g的PDM配制的、无机复合聚铝与PDM复合质量比为20:1、10:1、5:1的复合混凝剂PAC/PDM、复合聚铝1/PDM、复合聚铝2/PDM,比单独使用同种无机混凝剂,分别约能减少10%～25%、8.6%～28.6%、7.1%～28.6%的无机药剂投加量,无机复合聚铝与PDM复合比例越低、PDM特征黏度越高,复合混凝剂脱浊效果越好。因此,PDM对低温低浊河网水具有明显的强化混凝脱浊效果。     

Palm oil mill effluent pretreatment using Moringa oleifera seeds as an environmentally friendly coagulant: laboratory and pilot plant studies

This research paper covers the suitability of the coagulation–flocculation process using Moringa oleifera seeds after oil extraction as a natural and environmentally friendly coagulant for palm oil mill effluent treatment. The performance of M. oleifera coagulant was studied along with the flocculant KP 9650 in removal of suspended solids, organic components and in increasing the floc size. The optimum values of the operating parameters obtained from the laboratory jar test were applied in a pilot‐scale treatment plant comprised of coagulation–flocculation and filtration processes. Pilot‐scale pretreatment resulted in 99.7% suspended solids removal, 71.5% COD reduction, 68.2% BOD reduction, 100% oil and grease removal and 91% TKN removal. In pilot plant pretreatment, the percentage recovery of water was 83.3%, and 99.7% sludge was recovered after dewatering in a filter press. Copyright © 2006 Society of Chemical Industry     

Azo dye removal by Moringa oleifera seed extract coagulation

In this paper, the ability of Moringa oleifera seed extract–among other natural coagulants–to remove several different types of dyes has been researched. Moringa oleifera has been demonstrated to have a high removal ability for anionic dyes. This study is particularly focused on testing the removal of an azo dye such as Chicago Sky Blue 6B (CSB). It has taken out the fast kinetic of coagulant action and the high potential of this coagulant agent to treat wastewater from dyestuff. Up to 99% of CSB removal has been achieved with M. oleifera extract dosage of 150, 200 and 250 mg l^?1 for 100, 160 and 200 mg l^?1 of initial CSB concentration, respectively. Temperature does not affect the coagulant process and a pH level greater than 8 has a negative influence. Lower CSB percentage removal is achieved by increasing the initial dye concentration, but an optimum relationship between dye amount removed and M. oleifera extract amount has been established and it appears to be between 0.7 and 0.9, depending on the initial dye concentration and the bulk of the remaining dye concentration.     

Preparation of a composite coagulant: Polymeric aluminum ferric sulfate (PAFS) for wastewater treatment

A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80 °C) and time (30–50 min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80 °C, 40 min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45 mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250 rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids.     

Preparation and performance of a high purity poly-aluminum chloride

Poly-aluminum chloride (PACl) is one of the common coagulants for water and wastewater treatment. A new Chinese national standard of PACl has been implemented, where the concentration of insoluble substances, iron and heavy metals is to be controlled strictly, then researches on the preparation of high-purity PACl are needed. This paper presents a novel method to prepare high-purity PACl which contains high aluminum oxide content (>10%), high basicity (>90%), and low insoluble substance (<0.04%), iron (<300 mg L^?1) and heavy metals. Samples taken from the Huangpu River were used to evaluate the coagulation performance of high-purity PACl in comparison with conventional PACl. The results demonstrate that for the whole dose range studied, high-purity PACls removed more turbidity than conventional PACl. On the other hand, when the dose was greater than 4 mg L^?1 as Al, the high-purity PACl showed great UV₂₅₄-absorbance removal capacity; which was even much greater at high does (e.g., 10 mg L^?1). This could be partly attributed to the charge effect where a relative high zeta potential in the test water was achieved by dosing high-purity PACl.     

Supercritical CO2 extraction of omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds

Supercritical carbon dioxide (SC-CO₂) was employed to extract omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds and partially defatted cake. For ground seeds, the supercritical extraction was carried out at temperatures of 40, 50 and 60 °C and pressures of 300 and 400 bar, and for the cold pressed partially defatted cake, the extraction was carried out with 300 bar at 40 °C and with 400 bar at 60 °C. The global extraction yields (X₀), oil solubility, fatty acid composition of the oil and tocopherol content were determined. The seed samples used in this work contained 54.3% oil, of which 50.5% was linoleinc acid (ω-3). The maximum extraction recovery for the seeds as 92% at 400 bar and 60 °C, but on one occasion a recovery of 99.1% oil was obtained when cold pressed extraction was employed, followed by supercritical extraction at 400 bar and 60 °C. A high tocopherol content of about 2–3 g/kg of oil was obtained.     

Preparation of mullite ceramic microfilter membranes using Response surface methodology based on central composite design

In this paper effect of free silica removal from mullite microfilter membranes using different sodium hydroxide (NaOH) concentrations at different temperatures and for different removal times was studied. The prepared membranes were subjected to XRD, SEM, porosity analysis, and mechanical strength measurement. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiments and analyze three operating parameters including; NaOH solution concentration, NaOH solution temperature and removal time. The optimum porosity of 49.4 was obtained with NaOH solution concentration of 35 wt% at temperature 75 °C and removal time equal to 8 h.Water flux and mechanical strength as important characteristics were measured for all the membranes. For the membrane with the optimum porosity, water flux, mechanical strength, and free silica removal percentage were 61.7 kg/m² h, 21.6 MPa, and 28.2%, respectively. The maximum rejection percentage was 97.2% and emulsion flux for this state was 15.6 kg/m² h at temperature 25 °C and cross flow velocity of 1.5 m/s.     

高铁酸钾的制备及其对低温低浊水的处理

为了研制高效和安全的混凝剂,采用次氯酸盐氧化法制备高铁酸钾,对高铁酸钾处理低温低浊水源水进行研究。试验表明:采用次氯酸盐法制取的高铁酸钾稳定性高,产率和纯度较高;高铁酸钾具有混凝作用,对源水浊度去除效果好于聚合氯化铝,在源水浊度为20NTU,pH值为7.7,水温为6℃的条件下,投加高铁酸钾30mg/L,滤后水浊度为0.2NTU,高铁酸钾具有消毒作用,经其处理的源水细菌总数降为10个/mL,大肠菌群数降为0个/L,其浊度和细菌学指标均能满足国家生活饮用水一级标准。     

Kinetic studies of the oxidation of quercetin,rutin and taxifolin in the basic medium by (ethylenediaminetetraacetato) cobalt(III) complex

The quercetin in 0.01 M NaOH solution underwent steady oxidation when it was exposed to air with the formation of the quinone product. For the taxifolin and rutin, the oxidation occurred only when the solutions were saturated with O₂, but very slowly. The kinetics of the oxidation of flavonoids in 0.01 M NaOH solution by Co(edta)^? complex was carried out and the rate constants are 3.44 × 10², 1.04 × 10^? 1 and 1.46 × 10^? 2 M^? 1 s^? 1 for quercetin, rutin and taxifolin, respectively, at μ = 0.10 M LiClO₄. The deprotonation of the C₃ hydroxyl group and the conjugation between pyrone and catechol rings account for the reactivity of quercetin.     

Relevance of ions in pressurized fluid extraction of carbohydrates and phenolics from barley hull

The removal of total carbohydrates and phenolics from the hull of a new barley variety BT 584 using solid-liquid batch and aqueous pressurized fluid (ethanol or ionic liquid) extractions were evaluated. Using pressurized fluids, temperature was the most significant variable for the extraction of biocompounds from barley hull. The highest phenolics extraction (189.1 ± 3.1 mg/g hull) was obtained using pressurized aqueous ionic liquid while the highest carbohydrates extraction (450.3 ± 7.8 mg/g hull) was obtained using pressurized aqueous ethanol. The predicted solubility of ferulic acid and glucose in water, ionic liquid or carbonic acid, and the acid dissociation constant of the compounds studied allowed proposing an extraction mechanism based on biomass interaction with ionic species formed during pressurized fluid extraction. The anionic species facilitated removal of phenolics while the interaction of cationic/anionic species facilitated removal of carbohydrates from barley hull biomass.     

Behaviour of Inorganic Coagulants in Secondary Effluents from a Conventional Wastewater Treatment Plant

An experimental laboratory scale study was conducted to compare the effectiveness of three inorganic coagulants — aluminium sulphate, ferric chloride and polyaluminium chloride (PAC) — in reducing the turbidity of secondary effluents from a conventional wastewater treatment plant. For each inorganic coagulant, the dose and the pH of coagulation were optimized. The results enabled the selection of the most appropriate coagulant, its dose and the optimal operational conditions to obtain the required water quality (3-5 NTU) for re-use in agricultural drip irrigation systems. PAC was identified as the most suitable coagulant/flocculant for reducing the turbidity of this type of water. The optimal conditions corresponded to pH 6 and a dose of PAC of 20 mg/l, but the recommended conditions are 50 mg/l for pH 8 (the initial pH of the water) to obtain a turbidity reduction of 90%, which is independent of the initial turbidity of water (i.e. 5-32 NTU).     

Optimization of enzymatic pretreatment for n-hexane extraction of oil from Silybum marianum seeds using response surface methodology

An investigation on enzymatic pretreatment for n-hexane extraction of oil from the Silybum marianum seeds was conducted. The optimum combination of extraction parameters was obtained with the response surface methodology (RSM) at a four-variable and five-level central composite design (CCD). The optimum parameters of enzymatic pretreatment were as follows: enzyme concentration of 2.0% (w/w), temperature of 42.8 °C, reaction time of 5.6 h, and pH of 4.8. After enzymatic pretreatment, the oil was extracted by n-hexane for 1.5 h, and the oil yield on a dry basis was 45.70%, which well matched with the predicted value (45.86%). The results of the effects of the enzymatic pretreatment for n-hexane extraction of oil from the aspects of oil yield, microstructure and the fatty acid compositions showed that the enzymatic pretreatment had not affected on the fatty acid compositions, but could cause structure breakage of the S. marianum seeds and accelerate releasing extra oil, which increased the oil yield by 10.46% compared with n-hexane extraction for 1.5 h without enzymatic pretreatment, and confirmed the efficacy of enzymatic pretreatment for n-hexane extraction of oil from the S. marianum seeds.     

Selective boron extraction by polymer supported 2-hydroxylethylamino propylene glycol functions

Boron sorption ability of polymer supported 2-hydroxyethylamino propylene glycol functions was investigated. 2-hydroxyethylamino propylene glycol was prepared by reaction of glycidol with excess ethanolamine in N-methyl, 2-pyrrolidone (NMP). This was reacted with terpolymer of glycidyl metacrylate (0.4 mol) with methyl metacrylate (0.5 mol) and divinylbenzene (0.1 mol) which was prepared in spherical beads form (210–422 μm) by suspension polymerization.The resulting terpolymer having hydroxyethylamino propylene glycol functions (1.82 mmol g⁻¹) was found to be as efficient as previously reported iminodipropylene glycol functional resins in removal of trace boron from water. The resin showed a boron loading capacity of 1.6 mmol g⁻¹. Nearly second-order kinetics, with respect to the boric acid (k = 1.65 mol l⁻¹ s⁻¹, with a correlation factor of 0.99129) was determined in non-buffered conditions.It was observed that, more than 95% of boron is extracted by this resin from very dilute H₃BO₃ solution (100 ppm initial concentration) in less than 30 min of contact time. Splitting of sorbed boron can be achieved by simple acid leaching (4 M HCl) and regenerated by NaOH (0.1 M) solution.     

Dynamic light scattering studies on the aggregation behavior of tributyl phosphate and straight chain dialkyl amides during thorium extraction

Dynamic light scattering (DLS) studies were carried out to investigate the aggregation behavior of 1.1 M solutions of tributyl phosphate (TBP), N,N-dihexyl octanamide (DHOA) and of N,N-dihexyl decanamide (DHDA) in n-dodecane equilibrated with varying concentrations of nitric acid (0.1–6 M) and of Th (10–200 g/L). There was a gradual increase in thorium extraction with increased aqueous phase acidities. A significant enhancement in the aggregate sizes was observed with increasing concentration of thorium in the organic phase. The effect of 1-octanol as phase modifier was also investigated on the aggregation behavior of extracted species for TBP system.     

A novel cross-linked polyzwitterion/anion having pH-responsive carboxylate and sulfonate groups for the removal of Sr2+ from aqueous solution at low concentrations

A novel cross-linked polyzwitterion (CPZ) was synthesized via cycloterpolymerization of N,N-diallyl-N-sulfopropylammonioethanoic acid (92.5 mol%), a cross-linker 1,1,4,4-tetraallylpiperazinium dichloride (7.5 mol%), and sulfur dioxide (100 mol%) in the presence of azoisobutyronitrile in dimethylsulfoxide at 60 °C. CPZ, upon treatment with NaOH, was converted into a cross-linked polyzwitterion/anion (CPZA). The experimental data for the adsorption of Sr²⁺ on CPZA fitted the pseudo-second-order kinetic model and Freundlich as well as Temkin isotherm models. The adsorption process was spontaneous and exothermic in nature with negative values for both ΔG and ΔH. The low activation energy of 7.18 kJ/mol indicated the adsorption as a favorable process. The removal for the initial concentrations of 200 ppb and 1000 ppb (i.e., 1 ppm) of Sr²⁺ ions was observed to be 87% and 92%, respectively. An efficient synthetic access to the resin and excellent adsorption capacity and desorption would enable its use in the treatment of radioactive nuclear waste containing Sr²⁺ ions. The CPZA provided an opportunity to test the efficacy of a zwiiterionic/anionic group in the removal of Sr²⁺ ions in low concentrations.     

Fractionated extraction of saponins from Brazilian ginseng by sequential process using supercritical CO2, ethanol and water

Saponins are surfactants that reduce the surface tension of aqueous solutions, besides having pharmacological actions. In order to extract and fractionate saponins from Pfaffia glomerata roots and Hebanthe eriantha roots using supercritical technology, fractionated extracts were obtained from a sequential process in fixed bed using supercritical CO₂ (scCO₂), ethanol, and water as solvents. All extractions were carried out in four sequential steps, at 50 °C and 300 bar. In the first step, pure scCO₂ was used as solvent, while (a) scCO₂/etanol (70:30, w/w); (b) ethanol, and (c) ethanol/water (70:30, v/v) were used as solvents in the three subsequent steps. The extracts were analyzed by thin layer chromatography (TLC) and surface tension. The extraction yields of the four steps were 0.16, 0.55, 1.00, and 6.90% for P. glomerata roots, and 0.17, 0.58, 0.89, and 28% for H. eriantha roots, showing a predominance of high polarity compounds in these species. TLC analysis showed that the extraction process was selective according to the polarity of the solvent, and provided extracts containing different saponins, except for scCO₂ extraction. The extracts from the extraction using ethanol + scCO₂ (Step 2) showed the greatest ability to reduce the surface tension of water from 72 mN m⁻¹ (pure water) to 25 mN m⁻¹, suggesting that this step was the best for extraction of less polar saponins in the extracts. The critical micelle concentration (CMC) values were approximately 2 and 8 g L⁻¹ for P. glomerata and H. Eriantha, respectively. These results confirmed the efficacy of the extraction process under study.     

复合聚铝用于冬季太湖水的混凝脱浊研究

将特征黏度系列化的聚二甲基二烯丙基氯化铵(PDM)与聚合氯化铝(PAC)复合用于冬季低温太湖原水强化混凝脱浊处理。由混凝烧杯实验,考察了PAC/PDM复合比例、PDM特征黏度对脱浊效果及絮团沉淀性能的影响,并与经预加氯处理的太湖水的相应处理结果作对比。结果表明,对浊度在24~26 NTU,温度为5~9℃,藻含量为8.01×103个/mL的太湖水,在与某市某水厂混凝强度相近的搅拌强度下,要达到其2 NTU沉淀池出水的余浊标准,PAC投加量3.28 mg/L,而复合比例分别为20∶1、10∶1、5∶1的PAC/PDM复合混凝剂所需PAC投加量随PDM特征黏度0.55、1.53、2.47 dL/g的增加,分别为2.93~2.83,2.70~2.60,2.62~2.51 mg/L,相应的PAC投加量减少的幅度分别为10.67%~13.72%,17.68%~20.73%,20.12%~23.48%;当沉淀出水浊度要求提高至1 NTU时,PAC需4 mg/L的投加量,复合混凝剂需3.77~3.04 mg/L的投加量,相对于PAC可减少投加量5.75%~24.00%。可见PDM明显提高了PAC的混凝脱浊效果,且PAC/PDM复合配比越低,PDM特征黏度越高,复合混凝剂的脱浊效果与沉淀性能越好。此外,PAC/PDM复合混凝剂有可能通过减少预加氯的投加量,来减少卤代有机物的形成机会,增强供水水质安全性。     

Was pretreatment beneficial for more biogas in any process? Chemical pretreatment effect on hydrogen–methane co-production in a two-stage process

The study focused on the mesophilic anaerobic hydrogen production from PPS (pulp and paper sludge) and FW (food waste) pretreated by NaOH or H₂SO₄, and the subsequent thermophilic anaerobic methane production with the effluent in a two-stage process. The maximum hydrogen yield (78.35 mL g^?1 VS_fed) which was 50.21% higher than that of CK, was achieved when 10 g NaOH/100 g TS_substrate was used. However, the maximum methane yield (383.8 mL g^?1 VS_fed) was obtained in CK as well as 64% SCOD removal efficiency was achieved. In short, NaOH/H₂SO₄ pretreatment was suitable to enhance the hydrogen production.