Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.

Influence of Polyaluminum Chloride Residue on the Strength andMicrostructure of Cement-Based Materials

In this paper,cement and dechlorinated Polyaluminum Chloride Residue(PACR)have been used to prepare a net slurry and mortar specimens.Two hydration activity indicators have been used to quantitatively analyze the dechlorinated PACR hydration activity.In particular,the effect of dechlorinated PACR content on the compressive strength of mortar has been assessed by means of compressive strength tests.Moreover,X-ray diffraction(XRD)and scanning electron microscopy(SEM)have been employed to observe the microstructure of the considered hydration products.The following results have been obtained.The 28th day activity index of the dechlorinated PACR is 75%,and therefore it meets the criterion for the use of active admixture.The increase in the content of the dechlorinated PACR tends to reduce the compressive strength of mortar specimens,however,it is beneficial to its later strength growth.When the content is not greater than 10%,the strength remains unchanged,otherwise,it decreases.The PACR does not form a new crystalline phase in the cement slurry,and the dechlorinated PACR remains active until the age of the 28th day.The inclusion of the PACR mainly deteriorates the early strength of the cement slurry,but it promotes the production of hydration products in the cement slurry after the 7th day.

Features and mechanism for coagulation－flocculation processes of polyaluminum chloride

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Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Coagulation mechanisms of polyaluminum chloride(PACl) at various dosages were studied using a conventional jar test at different final and initial pH values during treating kaolin suspension. The optimal final pH and dosages for PACl were obtained based on residual turbidity and zeta potential of flocs. The coagulation zones at various PACl dosages and solution p H values were developed and compared with those of alum. It is found that the optimal mechanism under acidic condition is charge neutralization, while alkaline condition will facilitate the coagulation of PACl. Both charge neutralization coagulation and sweep coagulation can achieve high coagulation efficiency under the alkaline condition ranging from final p H 7.0 to 10.0. Stabilization, charge neutralization destabilization, restabilization and sweep zones occur successively with increasing PACl dosages with the final p H values fixed at 7.0 and 8.0, but restabilization zone disappears at final p H 10.0. When the final p H is not controlled and consequently decreases with increasing PACl dosage, no typical sweep zone can be observed and the coagulant efficiency decreases at high PACl dosage. It seems that the final pH is more meaningful than the initial p H for coagulation. Charge neutralization coagulation efficiency is dominated by zeta potential of flocs and PACl precipitates. The charge neutralization and sweep coagulation zones of PACl are broader in the ranges of coagulant dosage and p H than those of alum. The results are helpful for us to treat water and wastewater using PACl and to understand the coagulation process of PACl.

Preparation and characterization of organic polymer modified composite polyaluminum chloride

Compared with traditional aluminum salts, polyaluminum chloride （PACI） has better coagulation-flocculation performance in turbidity removal. However, it is still inferior to organic polymers in terms of bridging function. In order to improve the aggregating property of PACl, different composite PACl flocculants were prepared with various organic polymers. The effect of organic polymer on the distribution or Al（Ⅲ） species in composite flocculants was studied using ^27TAl NMR and Al-ferron complexation methods. The charge neutralization and surface adsorption characteristics of composite flocculants were also investigated. Jar tests were conducted to evaluate the turbidity removal efficacy of organic polymer modified composite flocculants. The study shows that cationic polymer and anionic polymer have significant influences on the coagulation-flocculation behaviors of PACl. Both cationic and anionic polymers can improve the turbidity removal performancc of PACl but the mechanisms arc much different： cationic organic polymer mainly increases the charge neutralization ability, but anionic polymer mainly enhances the bridging function.

Preparation of high concentration polyaluminum chloride with high content of Al_b or Al_c

A novel membrane distillation concentration method was used m prepare high concentration polyaluminum chloride （PAC1） with high content of AID or Ale. 2.52 mol/L PACl1 with 88% Alb and 2.38 mol/L PACl2 with 61% Ale were successfully prepared. Three coagulants, AlCl3, PACl1 and PACl2 were investigated on their hydrolysis behavior and speciation under different conditions. The effects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a significant effect on Al species distribution for the three coagulants. Dilution ratio had little effects on Alb and Alc distribution in whole dilution process except the beginning for PACl1 and PACl2. The results indicated that transformation of Al depends largely on their original composition. AlCl3 was the most unstable coagulant among these three coagulants during hydrolysis process. PACl1 and PACl2 with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less affected by the hydrolysis conditions and could maintain high speciation stability under various conditions.

Effects of Slow-Mixing on the Coagulation Performance of Polyaluminum Chloride （PACI）

Conventional jar tests and on-line size monitoring were used to investigate the effects of slow-mixing intensity and duration on residual turbidity and floc size during charge neutralization coagulation and sweep floc- culation with polyaluminum chloride. The compensatory effect of slow-mixing on coagulation performance fol- low!ng inadequate_or excessive rapid-mi_xing was also examined. It is found that slowTmixing intensity has a more marked positive ettect on charge neutralization coas;ulatlon tlaan on sweep tlocculatlon. llle optimal root-mean- square velocity gradient, G, for slow-mixing is 15 s-＇ for both coagulation mechanisms, and charge neutralization coagulation requires a longer slow-mixing duration. The optimal slow-mixing duration, based on residual turbidity,is longer than the time to tbrm the largest mean Ilocs. The optimal product of G and mixing duration, GT, lbr slow-mixing during charge neutralization coagulation （13500） are higher than that during sweep flocculation （4500） and both are less than the range of values recommended by the American Water Works Association （24000-84000）.The optimal GT value under various slow-mixing conditions increases with G. Appropriate extension＇of slow-mixing duration during charge neutralization coagulation can improve coagulation performance after an inadequate or excessive rapid-mixing duration, but during sweep flocculation, appropriate shortening of slow-mixing duration after an excessive rapid-mixing or appropriate extension of slow-mixing duration after an inadequate rapid-mixing is favorable.

Preparation of High Concentration Polyaluminum Chloride with High Al_c Content by Membrane Distillation

A direct contact membrane distillation（DCMD）process was applied to prepare high concentration polyaluminum chloride（PACl）with high Alc content.The changes in total Al concentration（AlT）and Al species distribution were investigated.The results showed that AlT increased but the flux decreased with operating time during the DCMD process.The Alc content increased from 65%to 81%while the Alb content decreased from 34% to 18%,and the Ala content was almost 1%in the process.2.1 mol·L 1PACl with 81%Alc was successfully prepared by DCMD method.Thus the DCMD is an effective method for preparing high concentration PACl with high Alc content.

Synergistic coagulation of bauxite residue-based polyaluminum ferric chloride for dyeing wastewater treatment

Considering that Fe,Al elements in bauxite residue are active components for water purification,an effective polyaluminum ferric chloride(PAFC)coagulant derived from bauxite residue,with Fe2O3 content>5.1%,Al2O3%>6.5%,basicity>65%,was successfully prepared.The effect of as-prepared PAFC on the zeta potential for printing and dyeing wastewater was investigated.Comparing with polyferric chloride(PFC)and polyferric sulfate(PFS)for printing and dyeing wastewater treatment,prepared bauxite residue-based PAFC exhibited the optimal performance in the aspects of chromaticity and chemical oxygen demand(COD)removal rate.Furthermore,the combination of bauxite residue-based PAFC and PFS for synergy coagulation of such wastewater demonstrated an obvious positive effect.With the proportion between as-prepared PAFC and PFS to be 2.5:1,the COD of treated wastewater could be further reduced to meet the national level A standard of China,providing a promising route to solve the problem of substandard printing and dyeing sewage outfall by a simple coagulation strategy.

Electrokinetic characteristic and coagulation behavior of flocculant polyaluminum silicate chloride (PASiC)

The electrokinetic characteristics and coagulation behaviors of polyaluminum silicate chloride (PASiC) and polyaluminum chloride (PAC) were studied and compared by streaming current (SC) measurement and jar test method. The experimental results showed that the interaction between polysilicic acid characterized negative charge and hydrolyzed aluminum species result in a decrease of the charge neutralizing ability of PASiC, compared to PAC. The decrease has a close relationship with the basicity ( B ) and Al/Si molar ratio in PASiC. The less the B value and the Al/Si molar ratio, the lower the charge neutralizing ability of PASiC is. In contrast, the preparation technique for PASiC affects the charge-neutralization of PASiC to a smaller extent. In addition, compared with PAC, PASiC may enhance aggregating efficiency and give better coagulating effects.

Preparation and Characterization of γ-Al2O3 by Polyaluminum Chloride with High Al13 Content

In this paper a polyaluminum chloride solution with high Al13 content was prepared and used as raw material for preparation ofγ-Al2O3.The texture and crystalline phase of the prepared alumina samples were characterized by energy dispersive X-ray spectroscopy(EDX) ,X-ray diffraction,transmission electron microscope(TEM) and nuclear magnetic resonance(NMR) analyses.The effects of alkaline solution and calcination temperature were investigated.The results showed that alkaline solution including NH3·H2O and NaOH had little effect on the alumina sample formation.The impurities of NH4Cl and NaCl in solution can be removed through repeated washing by EDX analysis.Calcination temperature had a significant effect on alumina crystal phase.The alumina sample can transform completely toγ-Al2O3 in the subsequent heating from 600°C to 800°C.It is very interesting that Al13 can be existed inγ-Al2O3 phase even after calcinations.The results indicate that polyaluminum chloride with high Al13 content is an effective material to prepareγ-Al2O3.

Quantitative model for species distribution of hydroxy polyaluminum chloride

The species distribution of hydroxy polyaluminum chloride (PAC, Al T=0.1mol/L) solutions prepared through two different types of base injection was studied and compared quantitatively by Al Ferron timed complex colorimetric method(AFM) and 27 Al NMR spectroscopy method (ANM), and was simulated by using a quantitative calculating procedure of chemical equilibrium in MINEQL model. The results suggest that methodology of synthesis is very important for determining species distribution in the preparation of PAC solutions. In the PAC solution prepared by micro injection of base method(MIBM), there are at least five kinds of species including a kind of monomeric species Al 3+ , three kinds of polymeric species Al 2(OH) 4+ 2, Al 7(OH) 4+ 17 , Al 13 O 4(OH) (7- n )+ 24+ n ( n =0,2)and an aggregate of Al 13 or a solid phase Al(OH) 3 (aq.). Whereas in the PAC solution prepared by instantaneous injection of base method (IIBM), there are a kind of monomeric species Al 3+ , two kinds of polymeric species Al 2(OH) 4+ 2, Al 13 O 4(OH) (7- n )+ 24+ n ( n =0,2) and a solid phase Al(OH) 3(am). The change of species distribution in the PAC solution depends on preparing method, B(OH/Al) value and concentration.

A novel method to synthesize polyaluminum chloride with a membrane reactor

Al 13 or Alb is usually regarded as the most efficient species of polyaluminum chloride(PAC), the performance flocculant for water treatment. This paper was intended to report a new method to synthesize PAC with high content Al b, by using the membrane reactor. NaOH solutions were managed to permeate slowly through the micropores of ultrafiltration membrane into AlCl 3 solutions under the suitable transmembrane pressure(TMP). Meanwhile NaOH drops size was limited to nano scale, resulting in dramatical reduction of the characteristic diffusion time and great increment of contact interface between the strong base and Al ions in solution to favor the formation of Al(OH) - 4, the precursor of Al 13 , so few precipitates and much Al b are produced. When the initial concentration of AlCl 3/NaOH is 0 40/2 0 (mol/L), MWCO =10000, TMP =0 0085 MPa, T =305 K and B (molar ratio of OH -/Al 3+ )=2 25, the quantity of Al b attains about 80%. The results of 27 Al NMR determination showed that the Al 13 content is equal to Al b content. And our PAC product has shown better flocculation effects than the commercial product.

Effect of Polyethylene Glycol on the Properties of γ-Al_2O_3 Formation by Polyaluminum Chloride

A polyaluminium chloride solution with high Al 13 content self-prepared was used as material for preparing the spherical γ-Al 2 O 3 by the sol-gel and oil-drop method. Polyethylene glycol with different molecular mass was used as surfactant to investigate the effect on property of γ-Al 2 O 3 . The physical property was characterized by 27 Al NMR (nuclear magnetic resonance) spectra, X-ray diffraction, FT-IR (Fourier transform infrared spectroscopy) and TG-DTA (thermogravimetric-differential thermal analysis). The results showed that surface area, pore volume and pore size of γ-Al 2 O 3 all increased with the increase of polyethylene glycol molecular mass in the experimental research range, and polyethylene glycol 10000 was the most suitable pore forming additive. γ-Al 2 O 3 with surface area of 339 m 2 ·g 1 , pore volume of 0.59 cm 3 ·g 1 and pore diameter of 6.9 nm were obtained at 450 °C.

Synchronous removal of CuO nanoparticles and Cu2+ by polyaluminum chloride-Enteromorpha polysaccharides: Effect of Al species and pH

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid(HA) to form composite contaminants.As an innovative recycled coagulant aid,Enteromorpha polysaccharides(Ep) were associated with polyaluminum chloride(PACl)(denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+and HA in this study.The influence of different Al species coagulants(AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail.Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep.Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects.For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions.Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems(bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species).Similarly,due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.

改性沸石/聚合氯化铝造粒复合材料对水中氨氮和磷的吸附性能研究

以改性沸石(MZ)和聚合氯化铝(PAC)为原料,添加粘结剂聚乙烯醇(PVA)和造孔剂碳酸氢钠(NaHCO_(3)),制备出可同步脱氮除磷的复合颗粒材料(MZP),并探究了投加量和pH等因素对氨氮和磷吸附性能的影响。结果表明,在MZP投加量为7 g/L,pH为6~8条件下,MZP对氨氮和磷的去除率均高于84%。MZP对氨氮和磷的吸附符合Freundlich吸附等温线模型,且吸附过程受液膜扩散和颗粒内扩散共同控制,符合准二级动力学模型,吸附过程MZP对氨氮和磷的最大理论吸附量分别为5.92、2.25 mg/g。共存离子对MZP吸附氨氮和磷有一定影响。经过5次吸附-解吸再生循环利用后,MZP仍能保持74%的氨氮去除率和52.6%的磷去除率。结合材料表征分析结果,MZP对氨氮的吸附主要为离子交换,对磷的吸附主要为静电吸附和配体交换。

煤气化渣除杂富铝制备聚合氯化铝实验研究

煤气化渣是煤气化工艺产生的固体废弃物,随着煤气化工艺的广泛推广与应用,大量煤气化渣的产生对生态环境造成威胁的同时也制约着煤化工行业的发展。为实现煤气化渣的资源化、工业化利用,以煤气化粗渣为研究对象,对其矿物赋存形态和化学组成进行分析,提出煤气化渣净化除杂-酸浸提铝制备聚合氯化铝(polyaluminum chloride,PAC)的总体构思。利用煤气化渣中各元素与酸溶液的反应活性差异,在低酸体系下浸出Fe^(2+),Ca^(2+)及少部分Al^(3+),再利用离子沉淀pH差异,将钙、铁与煤气化渣选择性分离,实现酸渣富铝。以富铝酸渣为原料,酸浸制备PAC前驱体。考察铝酸钙粉添加量、聚合温度、聚合时间对产品品质及絮凝效果的影响。结果表明:在60%理论耗酸量下,煤气化渣浸出Al^(3+),Fe^(2+),Ca^(2+),将反应液pH调至3.5,Al^(3+)选择性沉淀,固液分离后制备富铝渣,钙、铁的去除率可达84.06%和79.79%,Al_(2)O_(3)质量分数由原来的10.84%提升至14.38%;富铝酸渣添加酸后再次溶出,酸溶液中氧化铝质量浓度可达到28.4 g/L;按固液比为10 g∶100 mL向酸溶液添加铝酸钙粉,在80℃下聚合2.5 h,可获得符合GB/T 22627-2022要求的PAC产品;通过FTIR和XRD对PAC产品进行表征,表明生成的产品为PAC,将该产品应用于模拟废水中,去浊率高达92.90%。

水处理用絮凝剂对发光细菌的联合毒性研究

随着絮凝剂在污水污泥处理过程的广泛使用,其残留在水处理系统中可能存在的单一或联合毒性效应日益受到关注。以聚合硫酸铁(PFS)、聚合氯化铝(PAC)和聚丙烯酰胺(PAM)为研究对象,通过发光细菌单一毒性和联合毒性试验探讨其可能造成的毒性效应。结果表明:1)对于单一毒性效应,PFS、PAC和PAM对发光细菌抑制效应的半数效应浓度(EC_(50))分别为29.41、71.82和1072.64 mg/L,毒性效应大小为PFS>PAC>PAM。2)对于二元絮凝剂联合毒性效应,PFS-PAM在毒性比为1∶1混合时具有协同作用,而PAC-PAM在毒性比为1∶3和3∶1混合时均存在拮抗作用。3)采用浓度加和(CA)和独立作用(IA)模型对联合毒性进行预测,PFS-PAM组合实测值与CA模型的预测值相近,而PFS-PAC和PAC-PAM组合实测值与IA模型预测结果相近。4)三维偏差响应面结果显示,试验观测值与CA模型预测值的偏差(dCA)和试验观测值与IA模型预测值的偏差(dIA)会随着絮凝剂浓度变化而变化,CA模型在PFS和PAC浓度较高时拟合程度较好,而对于PAC-PAM体系,IA模型的拟合程度较CA模型好。研究发现,PFS和PAC对发光细菌的毒性效应较强,PFS与PAM混合使用可能会增加毒性效应,对水处理系统中的微生物造成环境风险。

市政污泥热解残渣理化性能与利用潜势分析

污泥热解残渣作为污泥处理产物,具有丰富的硅、铝、铁等化合物,是一种潜在的可回收利用资源。文章以污泥热解残渣为原料,通过物理、化学相结合方法制备了多孔沸石和聚合氯化铝铁,并探究其污废水处理性能。试验结果表明,污泥残渣通过水热法合成的沸石表现出典型的多孔结构,在常温下对水中亚甲基蓝的吸附最大可达31 mg/g。同时,通过酸浸和聚合反应合成的聚合氯化铝铁对污水厂污水显示出优异的除磷效果,处理后出水总磷可稳定达到《陕西省黄河流域污水综合排放标准》标准。文章通过合成沸石、絮凝剂实现了污泥的无害化和高效化处置,为污泥残渣的资源化应用提供了一条路径。

Preparation of high concentration polyaluminum chloride by chemical synthesis-membrane distillation method with self-made hollow fiber membrane

A method of direct contact membrane distillation （DCMD） with a self-made hollow polyvinylidene fluoride membrane was applied to prepare high concentration polyaluminum chloride （PACl） with high Alb content based on chemical synthesis. The permeate flux and Al species distribution were investigated. The experimental results showed that the permeate flux decreased from 14 to 6 kg/（m2·hr） at the end of the DCMD process, which can be mainly attributed to the formation of NaCl deposits on the membrane surface. The Alb content decreased slightly, only from 86.3% to 84.4%, when the DCMD experiment finished, correspondingly the Alc content increased slightly from 7.2% to 8.5%, and the Ala content remained at 7% during the whole DCMD process. A PACl with Alb content of 84% at total aluminum concentration 2.2 mol/L was successfully prepared by the chemical synthesis-DCMD method.