High phosphate removal using La(OH)3 loaded chitosan based composites and mechanistic study

Our present study was to prepare a biomass-supported adsorbents with high adsorptive capacity and high selectivity to prevent the accelerated eutrophication in water body. To this end, different metal hydroxide (La, Zr and Fe) first was successfully loaded on chitosan microspheres. Then the quaternary ammonium group with different content was introduced into the adsorbent by polymerization. By comparison of adsorption properties, chitosan-La(OH)₃-quaternary ammonium-20% (CS-La-N-20%) has strong adsorption to phosphate (160 mg/g) by immobilizing nano-sized La(OH)₃ within a quaternary-aminated chitosan and it maintain high adsorption in the presence of salt ions. The pH results indicated that the CS-La-N-20% would effectively sequestrate phosphate over a wide pH range between 3 and 7 without significant La³⁺ leaching. What's more, adsorption capacity on the introduce of positively charged quanternary-aminated groups was significantly higher than that of the unmodified adsorbents at alkaline conditions. The column adsorption capacity reached 1300 bed volumes (BV) when phosphate concentration decreased until 0.5 mg/L at 6 BV/hr. The column adsorption/desorption reveals that no significant capacity loss is observed, indicating excellent stability and repeated use property. Characterizations revealed that phosphate adsorption on CS-La-N-20% through ligand exchange (impregnated nano-La(OH)₃) and electrostatic attraction (positively charged quanternary-aminated groups). All the results suggested that CS-La-N-20% can serve as a promising adsorbent for preferable phosphate removal in realistic application.     

Migration of manganese and iron during the adsorption-regeneration cycles for arsenic removal

Fe-Mn binary oxide incorporated into porous diatomite (FMBO-diatomite) was prepared in situ and regenerated in a fixed-bed column for arsenite [As(III)] and arsenate [As(V)] removal. Four consecutive adsorption cycles were operated under the following conditions: Initial arsenic concentration of 0.1 mg·L⁻¹, empty bed contact time of 5 min, and pH 7.0. About 3000, 3300, 3800, and 4500 bed volumes of eligible effluent (arsenic concentration ⩽ 0.01 mg·L⁻¹) were obtained in four As (III) adsorption cycles; while about 2000, 2300, 2500, and 3100 bed volumes of eligible effluent were obtained in four As(V) adsorption cycles. The dissection results of FMBO-diatomite fixed-bed exhibited that small amounts of manganese and iron were transferred from the top of the fixed-bed to the bottom of the fixed-bed during As(III) removal process. Compared to the extremely low concentration of iron (<0.01 mg·L⁻¹), the fluctuation concentration of Mn²⁺ in effluent of the As(III) removal column was in a range of 0.01–0.08 mg·L⁻¹. The release of manganese suggested that manganese oxides played an important role in As(III) oxidation. Determined with the US EPA toxicity characteristic leaching procedure (TCLP), the leaching risk of As(III) on exhausted FMBO-diatomite was lower than that of As(V).     

TiO2@酵母复合微球固定床吸附荧光增白剂-VBL的研究

研究了Ti O2@酵母复合微球在固定床中吸附阴离子型荧光增白剂-VBL(FWA-VBL)的特性,考察了溶液p H(2.0~8.0)、床层高度(1~3 cm)、进水浓度(20~80 mg·L-1)和进水流速(5~11 m L·min-1)等因素对固定床吸附特性的影响.结果表明在溶液p H为2.0,床层高度为1 cm,进水浓度为80 mg·L-1和进水流速为5 m L·min-1时,吸附剂的最大吸附量为223.80 mg·g-1.BDST、Thomas和Yoon-Nelson模型均能很好地描述不同条件下动态吸附行为,相关系数均大于0.980.同时,Ti O2@酵母复合微球具有很好的再生性能,可以重复利用4次.     

Simultaneous removal of arsenic and antimony from mining wastewater using granular TiO2: Batch and field column studies

Coexisting arsenic (As) and antimony (Sb) in mining wastewater is a common and great concern. On-site simultaneous removal of As and Sb from mining wastewater was achieved by using a reusable granular TiO₂ column in this study. To evaluate the accuracy of the scale-up procedure, As and Sb adsorption from wastewater was studied in both large (600 g TiO₂) and small columns (12 g TiO₂) based on the proportional diffusivity rapid small-scale column tests (PD-RSSCTs) design. The comparable As and Sb breakthrough curves obtained from small and large columns confirmed the accuracy of the PD-RSSCT theory in the design of large-scale columns. Meanwhile, the consistent As and Sb adsorption results from batch and column experiments suggested that TiO₂ adsorption for As and Sb can be predicted from bench-scale tests. Charge distribution multi-site complexation (CD-MUSIC) and one-dimensional transport modeling integrated in the PHREEQC program were performed to study the adsorption behaviors of As and Sb on the TiO₂ surface. Coexisting ions, such as Ca^2 +, Mg^2 +, and Si^4 +, play an important role in As and Sb adsorption, and the breakthrough curves were well simulated after considering the compound ion effects. The results from this study highlight the surface reactions of As and Sb on TiO₂ and provide a practical way for on-site remediation of industrial wastewater.     

Adsorption and recovery of phosphate from water by amine fiber, effects of co-existing ions and column filtration

A weak-base adsorption fiber, acrylic amine fiber (AAF), was prepared for removal and recovery of phosphate from water. The adsorption properties of the AAF for phosphate and effects of co-existing ions were investigated using batch and column filtration experiments, scanning electron microscope, and Fourier transform infrared techniques. Experimental results showed that AAF had a high phosphate adsorption capacity of 119?mg/g at pH?7.0. The effects of calcium, sulfate, carbonate, nitrate, and fluoride showed that sulfate and calcium inhibited phosphate adsorption. However, AAF showed higher binding affinity toward phosphate than sulfate. Column filtration results showed that AAF could filter 1420 bed volumes of tap water containing 1.0?mg-P/L of phosphate. The saturated AAF could be regenerated using 0.5?mol/L hydrochloric acid solution and reused. After desorption, phosphate was recovered through precipitation of hydroxyapatite (Ca₅(PO₄)₃OH). The easy of regeneration, good adsorption performance, and the fiber morphology of AAF make it an attractive alternative for phosphate recovery from multiple water sources.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.     

Assembly of SPS/MgSi assisted by dopamine with excellent removal performance for ciprofloxacin

In this work, magnesium silicate-based sulfonated polystyrene sphere composites (SPS/MgSi) were synthesized by one-step (SMD1) and two-step (SMD2) methods. For SMD1, MgSi particles were densely assembled on the surface of SPS, assisted by complexation between Fe³⁺ and hydroxyl phenol. For SMD2, SPS/SiO₂ was firstly obtained by the same method as SMD1, and then SPS/SiO₂ was transformed directly to SPS/MgSi under hydrothermal conditions. Therefore, MgSi obtained by the two-step method had an interwoven structure. Compared to SPS, MgSi and SMD1, SMD2 presented a larger specific surface area and more negative surface charges. Therefore, SMD2 showed superior adsorption performance toward CIP with concentrations of 5, 10 and 50 mg/L, and for 50 mg/L, the equilibrium adsorption capacity could reach 329.7 mg/g. The adsorption process is fast and can be described by the pseudo-second-order kinetic model. The relationship between pH value and Zeta potential demonstrated that electrostatic interaction dominated the adsorption process. In addition, competitive adsorption showed that the effect of Na⁺ was negligible but the effect of Ca²⁺ was dependent on its concentration. Humid acid (HA) could slightly promote the absorption of CIP by SMD2. After five rounds of adsorption-desorption, the equilibrium adsorption capacity of SMD2 still remained at 288.6 mg/L for 50 mg/L CIP. Notably, SMD2 presented likewise superior adsorption capacity for CIP with concentrations of 10 and 50 mg/L in Minjiang source water. All the results indicated that this synthesis method is universal and that SMD2 has potential as an adsorbent for CIP removal from aquatic environments.     

海藻酸锆/聚N-异丙基丙烯酰胺半互穿网络凝胶球的除磷性能

利用离子交联和自由基聚合反应制备了一种海藻酸锆/聚(N-异丙基丙烯酰胺)半互穿网络凝胶球(ZA/PNIPAM),用于吸附水中的磷酸盐.考察了溶液初始pH、吸附剂投加量、初始磷酸盐浓度和共存阴离子等因素对凝胶球吸附性能的影响.结果表明:ZA/PNIPAM在pH=2时可获得较大的吸附能力;随着投加量的减少、初始磷酸盐浓度的升高,凝胶球的吸附性能逐渐增大;SO_4~(2-)对吸附性能影响较Cl~-和NO_3~-明显.准二级动力学模型和颗粒内部扩散模型可以较好地拟合动力学吸附数据,表明表面吸附和颗粒内部扩散是吸附速率的主要控制步骤.吸附等温线数据可以较好地被Freundlich模型描述,表明吸附过程为非均匀多分子层吸附.FTIR、XPS、零电荷点(pH_(pzc))的结果以及相关吸附数据揭示凝胶球吸附磷酸盐的机制为静电吸附(物理吸附)以及配位交换(化学吸附)的共同作用.经过4次循环再生后,ZA/PNIPAM吸附性能保持稳定,具有良好的重复使用性.     

固定床中好氧颗粒污泥动态吸附结晶紫染料

针对印染废水色度高,脱色难度大的问题,通过固定床工艺利用灭活的好氧颗粒污泥(AGS)对水中结晶紫(CV)进行动态吸附.通过对固定床高度、CV初始浓度和和流速对穿透曲线的影响进行探讨,采用Thomas模型和BDST模型对动态吸附试验所得数据拟合并获得了相应参数.试验结果表明,随着固定床高度的增加,穿透时间和饱和吸附时间延长;当CV初始浓度和流速增加时,穿透时间和饱和吸附时间急剧缩短.Thomas模型能够很好地描述AGS对CV的动态吸附动力学.当CV浓度为100mg/L,流速为8.3mL/min,固定床高度为20cm时AGS对CV的吸附动力学与Thomas模型拟合程度最好,相关系数为0.9813.BDST模型能准确预测穿透时间,平均误差小于10%.吸附CV染料后AGS可用无水乙醇进行再生.     

铁锰复合氧化物包覆海砂的吸附除磷研究

利用铁锰复合氧化物包覆海砂制备了一种用于污水除磷的新型颗粒状吸附剂,并对其表面特性与磷吸附行为进行了研究.扫描电镜(SEM)分析结果表明,包覆后海砂颗粒表面凹凸不平且多孔,BET比表面积由0.06增至2.52 m2·g-1.磷吸附实验结果表明,包覆后海砂对磷的吸附能力显著提高,最大吸附容量为1.01~1.23 mg·g-1,优于多数文献报道的负载改性砂颗粒吸附剂;吸附动力学更符合准二级动力学方程,推测磷在包覆海砂表面发生了化学吸附;溶液p H对磷吸附有一定影响,离子强度则影响不大;共存阴离子对磷吸附影响的大小顺序为Si O2-3CO2-3F-SO2-4Cl-.     

铁氮共掺杂生物炭对二级水溶解性有机物的吸附特性与长效性评价

为经济高效地去除污水厂二级水中溶解性有机物(DOM),采用铁氮共掺杂生物炭材料(Fe-N-C)作为新型吸附剂,系统分析了该新型碳材料对于二级水DOM的吸附性能、动力学过程、选择性和作用机制.此外,通过固定床吸附装置深入考察了该吸附材料的长效性和重复利用性.结果表明,Fe-N-C对于二级水DOM具有突出的吸附性能,投加量...     

Lead removal from water using organic acrylic amine fiber (AAF) and inorganic-organic P-AAF, fixed bed filtration and surface-induced precipitation

Granular porous sorbents were normally used for heavy metals removal from water. To search for the new commercial sorbent and treatment strategy, an organic acrylic amine fiber (AAF) and phosphorus loading inorganic-organic AAF (P-AAF) were prepared and used for lead (Pb) removal from water. A new strategy of inorganic-organic coupling technology was proposed for Pb removal, based on the hypothesis of surface-induced precipitation mechanism. The AAF showed a Pb adsorption capacity of 417 mg/g from the Langmuir fitting, while the column filtration technology was further applied to measure the adsorption edge and applications. Effects of different initial Pb concentrations, hydraulic retention time, and co-existing P were considered in the filtration experiments. The presence of 0.8 mg/L P in water significantly improved the Pb breakthrough point from 15,000 to 41,000 bed volumes of water spiked with 85 µg/L Pb, while the P-AAF fixed bed showed better removal of Pb than AAF SEM/EDX and XRD spectra were employed for determining the surface functional groups and the formation of surface-induced precipitation of pyromorphite (Pb₅(PO₄)₃OH) on AAF. This study verified the application of AAF sorbent for Pb removal and the enhanced effect of coating P on AAF, thus improved our fundamental understanding and application of the surface chemistry process of Pb with P.     

改性荔枝皮对水中Pb(Ⅱ)的动态吸附特性

以改性荔枝皮为吸附剂对Pb(Ⅱ)进行固定床动态吸附试验,考察了填料柱高(3.1、5.2和10.4 cm)、Pb(Ⅱ)溶液进水流速(2、4和6 mL/min)和初始ρ〔Pb(Ⅱ)〕(50、100和200 mg/L)对Pb(Ⅱ)的吸附穿透曲线和传质区长度的影响. 结果表明:降低柱高、增大流速、增大初始ρ〔Pb(Ⅱ)〕均会使穿透时间提前;柱高、流速和初始ρ〔Pb(Ⅱ)〕引起的传质区长度的平均变化率绝对值分别为0.076、0.090和0.004,可见与初始ρ〔Pb(Ⅱ)〕相比,柱高和流速对传质区长度的影响更大. 吸附穿透曲线的试验数据符合Thomas模型的使用条件(R2>0.95),吸附容量实测值(q_exp)大于59.1 mg/g,与Thomas模型预测值(q_cal)较为接近,说明内部扩散和外部扩散均非该吸附过程的限速步骤. 在仅改变流速或者初始ρ〔Pb(Ⅱ)〕时,穿透时间预测值和实测值间的最大误差分别为7.14%和8.45%,表明可以通过BDST(bed depth service time)模型确定固定床的使用周期.      

Electro-oxidation of Ni (II)-citrate complexes at BDD electrode and simultaneous recovery of metallic nickel by electrodeposition

The simultaneous electro-oxidation of Ni (II)-citrate and electrodeposition recovery of nickel metal were attempted in a combined electro-oxidation-electrodeposition reactor with a boron-doped diamond (BDD) anode and a polished titanium cathode. Effects of initial nickel citrate concentration, current density, initial pH, electrode spacing, electrolyte type, and initial electrolyte dosage on electrochemical performance were examined. The efficiencies of Ni (II)-citrate removal and nickel metal recovery were determined to be 100% and over 72%, respectively, under the optimized conditions (10 mA/cm², pH 4.09, 80 mmol/L Na₂SO₄, initial Ni (II)-citrate concentration of 75 mg/L, electrode spacing of 1 cm, and 180 min of electrolysis). Energy consumption increased with increased current density, and the energy consumption was 0.032 kWh/L at a current density of 10 mA/cm² (pH 6.58). The deposits at the cathode were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These characterization results indicated that the purity of metallic nickel in cathodic deposition was over 95%. The electrochemical system exhibited a prospective approach to oxidize metal complexes and recover metallic nickel.     

铈改性水葫芦生物炭对磷酸盐的吸附特性

本研究通过共浸渍-热解法开发了一种铈改性水葫芦生物炭吸附剂（Ce-BC）,用以去除实际废水中的磷酸盐,考察了Ce-BC投加量、废水pH值、反应时间及共存的竞争性离子对吸附过程的影响.结果表明,当Ce-BC投加量为0.4 g·L^-1,初始磷酸盐溶液pH值介于3~10时,Ce-BC对磷酸盐的吸附性能最佳,最大吸附量达到35.00 mg·g^-1.Ce-BC对磷酸盐的吸附过程符合准二级动力学模型,并能在1 h内达到98%的磷酸盐去除率,吸附速率快.此外,Ce-BC具有较高的抗阴离子干扰能力,且具有良好的再生性能,Ce-BC经过4次再生后仍能保持90%以上的初始吸附效率.场发射扫描电镜-能量色散光谱（FESEM-EDS）、傅里叶红外光谱（FTIR）、X射线衍射光谱（XRD）和X射线光电子能谱（XPS）等表征结果表明,Ce-BC对磷酸盐的吸附机制主要包括配体交换和内球络合.本研究制备的Ce-BC吸附剂,可以有效去除及回收实际生活污水中的磷酸盐,在避免水体富营养化的同时实现磷资源的回收利用.     

鸟粪石-沸石复合材料对水中镉的吸附性能研究

研究以氧化镁负载沸石回收污水中氮磷得到的鸟粪石-沸石复合材料(STR-NZ)为吸附剂,用于对水体中重金属镉的吸附去除.实验采用SEM-EDS、XRD和FTIR等手段对STR-NZ材料进行表征,并考察了投加量、初始pH和反应时间等对STR-NZ材料去除水中Cd~(2+)的影响.结果表明:氧化镁负载沸石材料主要以鸟粪石沉淀的方式实现对水中磷酸盐和氨氮的回收;STR-NZ对水溶液中Cd~(2+)的吸附量随pH的增大呈先增加后趋于平衡的趋势,当Cd~(2+)的初始浓度为50 mg·L~(-1)时,STR-NZ的最佳投加量为0.2 g·L~(-1),Cd~(2+)最大吸附量为249.35 mg·g~(-1), STR-NZ对Cd~(2+)的吸附动力学符合准二级动力学模型,对Cd~(2+)的等温吸附符合Langmuir等温吸附模型,STR-NZ主要通过Cd_5(PO_4)_3(OH)沉淀的方式实现对水中Cd~(2+)的去除.     

粟米糠-耐Pb菌株复合吸附剂固定床穿透曲线特性

以粟米糠(MC)为原料,添加自铅锌尾矿渣中分离的耐铅菌米曲霉(HA)制成粟米糠-耐Pb菌株复合吸附剂(MCH),研究固定床系统中MCH对Pb~(2+)的动态吸附特性,考察吸附柱高度、初始离子浓度、进水流速对穿透曲线特性的影响.研究结果表明,复合吸附剂在固定床系统中的吸附性能明显优于单一吸附剂;MCH对Pb~(2+)的吸附穿透时间与吸附柱高成正相关,与初始离子浓度和进水流速成负相关,传质区长度与吸附柱高成负相关,与初始离子浓度和进水流速成正相关;初始离子浓度对穿透曲线和传质区长度影响最小.采用BDST、Yoon-Nelson和Thomas模型拟合试验数据结果显示,在较高流速和初始离子浓度条件下,实测与BDST模型拟合数据的相对误差最小,其原因可解释为BDST模型忽略了内部扩散和质量传递间阻力的影响;在吸附柱较低、初始离子浓度或进水流速较大条件下,由于传质推动力过大以至传质区被瞬间穿透,吸附质在吸附柱内停留时间很短,Yoon-Nelson和Thomas模型无法准确预测其穿透时间和拟合穿透曲线;总体上对比其它模型,Thomas模型拟合穿透曲线的效果较好,说明在MCH固定床Pb~(2+)的吸附过程中没有轴向扩散且具有平推流作用.     

锆负载颗粒沸石改良底泥对水中磷酸盐的吸附行为

通过批量吸附实验考察了锆负载颗粒沸石改良底泥对水中磷酸盐的吸附特征,并采用分级提取法分析了被改良底泥中锆负载颗粒沸石所吸附磷酸盐的形态分布特征.结果发现,与Freundlich和Dubinin-Radushkevich模型相比,Langmuir模型可以更好地用于描述改良底泥对水中磷酸盐的吸附等温行为.改良底泥对水中磷酸盐的吸附动力学过程可以较好地采用准二级动力学模型和Elovich模型加以描述,膜扩散和颗粒内扩散共同构成了缓慢吸附阶段速率的限制步骤.溶液共存的SO_4~(2-)和HCO_3~-降低了改良底泥对水中磷酸盐的吸附,而共存的Na~+、K~+、Mg~(2+)和Ca~(2+)却增强了对磷酸盐的吸附,且Ca~(2+)的增强效果大于Mg~(2+),后者的增强效果又大于Na~+和K~+.改良底泥对水中磷酸盐的吸附能力明显强于未改良底泥,前者的最大单位吸附量为336 mg·kg~(-1),明显高于后者的最大单位吸附量(215 mg·kg~(-1)).被改良底泥中锆负载颗粒沸石所吸附的磷酸盐主要以较为稳定的NaOH-P和最为稳定的Res-P形态存在,不容易被重新释放出来.上述的研究结果显示,向底泥中添加锆负载颗粒沸石可以显著增加底泥对水中磷酸盐的吸附能力,锆负载颗粒沸石是一种有希望的可以用于底泥内源磷释放控制的底泥改良剂.     

纳米零价铁对升流式颗粒污泥床反硝化性能的影响

为探究连续流条件下,纳米零价铁(nZVI)对反硝化颗粒污泥(DGS)性能的影响,本文利用升流式污泥床(USB),系统考察了反应器脱氮效能、污泥形态和反硝化特性随进水nZVI浓度的变化规律.结果表明,当nZVI5 mg·L~(-1)时,反应器脱氮效能与对照期(nZVI=0 mg·L~(-1))相差很小,DGS活性略微增大.当nZVI浓度在5~10 mg·L~(-1)时,DGS对nZVI的生物抑制作用表现出一定适应性,污泥浓度和颗粒粒径仍保持增长趋势,但泥相中总铁含量明显增大,DGS活性开始降低.当nZVI浓度增至30 mg·L~(-1)时,反应器对COD和NO-3-N的去除率分别降至对照期的23.3%和20.3%.DGS因吸附大量nZVI而呈黑色,颗粒粒径减小,污泥表面短杆菌等微生物密度明显降低.停止投加nZVI后,污泥浓度与DGS活性的持续上升,使得反应器脱氮效能在20 d内基本恢复至对照期的水平.异养菌在颗粒表面的快速增殖是实现上述目标的主要原因.     

A new recycling material for removing phosphorus from water

In search of readily available and relatively inexpensive materials for phosphorus removal, waste oyster shell is a waste product from oyster-culturing farm and also presents a major disposal problem in itself. Activated oyster shell produced by pyrolysis at 750 °C exhibits promising performance as a suitable substance for phosphorus removal. The capacity of the activated oyster shell, in terms of equivalents of OH^? per gram of material, is about 80% than that of calcium hydroxide. However, the granular nature of activated oyster shell (AOS) makes it much easier to handle than lime. This would be a very important advantage for treatment facilities that cannot afford specialized powder handling facilities necessary for lime. Another advantage of AOS is its time-release properties, which can allow it to be added to reactors intermittently and still achieve consistent phosphate precipitation. Distribution of phosphate after contact with AOS indicates that adsorption does not play a significant role in phosphate removal with AOS. Rather, it appears that the phosphate is precipitated in the presence of Ca²⁺ and high pH as a key mechanism. Since it is produced from a waste product of mariculture, AOS is a sustainable precipitant for phosphate removal.