Recovery of waste rare earth fluorescent powders by two steps acid leaching

The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.

Recycling and depolymerization of waste polyethylene terephthalate bottles by alcohol alkali hydrolysis

In this work,a novel alcohol alkali hydrolysis method was explored for the preparation of terephthalic acid(TPA)from waste polyethylene terephthalate(PET).First,a series of single factor experiments on the depolymerization rate of waste PET bottles and the yield of TPA were conducted to determine the optimized experimental conditions,in terms of reaction time,reaction temperature,dosage of ethylene glycol and sodium bicarbonate,amount of distilled water and stirring rate.Then IR spectra and elemental analysis were carried out for the characterization of obtained product.Under optimal experimental conditions,over 98%PET can be depolymerized into the target product(TPA)and the purity and yield of TPA are over 97%and 94%,respectively.Both the experimental and analytical results support a feasible process for the preparation of TPA from waste PET.It is expected that this alcohol alkali hydrolysis method can promise an effective way for the sustainable recycling of waste PET.

Recovery of alkali and alumina from Bayer red mud by the calcification–carbonation method

Red mud produced in the Bayer process is a hazardous solid waste because of its high alkalinity; however, it is rich in valuable components such as titanium, iron, and aluminum. In this study, a novel calcification-carbonation method was developed to recover alkali and alumina from Bayer red mud under mild reaction conditions. Batch experiments were performed to evaluate the potential effects of im- portant parameters such as temperature, amount of CaO added, and CO2 partial pressure on the recovery of alkali and alumina. The results showed that 95.2% alkali and 75.0% alumina were recovered from red mud with decreases in the mass ratios of Na2O to Fe2O3 and of Al2O3 to Fe2O3 from 0.42 and 0.89 to 0.02 and 0.22, respectively. The processed red mud with less than 0.5wt% Na2O can potentially be used as a construction material.

Lactic Acid Fermentation from Coffee Ground Waste Hydrolysate by Lactobacillus rhamnosus

Lactic acid is an important organic acid that is widely used in the food,pharmaceutical,and cosmetic industries.Lactic acid was produced from coffee ground waste which contains fermentable sugars and is increasingly generated from our daily dietary life.Among 114 strains of Lactobacillus species,Lactobacillus rhamnosus ATCC 10863 was selected for the production of lactic acid from coffee ground waste.Through alkali pretreatment and saccharification,cellulose and hemicellulose in coffee ground waste were converted into fermentable sugars.Pretreatment experiments were conducted at various alkali solution,concentrations,and times.Alkali pretreatment with 35 g/L of KOH at 121oC for 60 min,the highest concentration of fermentable sugars was produced.The optimum concentration of Viscozyme L was 2%when saccharification was proceeded at 55oC for 7 days.The productivity of lactic acid fermentation was the highest(0.59 g/L/h)at 100 g of coffee ground waste(1x concentration),whereas the lactic acid concentration was the highest at 600 g of coffee ground waste(6x concentration).As the concentration of coffee ground increased,the lactic acid concentration was also increased,however,the amount was not proportional to the coffee ground waste used.In this study,it was found that coffee ground waste could be used as a culture medium for Lactobacillus rhamnosus ATCC 10863 through pretreatment and saccharification for the production of lactic acid.

Phosphorus Recovery from the Ash of Sewage Sludge Using NaOH by Heat Treatment-II—Reuse of the Alkali Water Generated by Phosphorus Recovery

The phosphorus recovery from the incinerated ash using NaOH by the heat treatment,was investigated.In this method,non-reacted NaOH containing alkali water was generated with the phosphorus recovery.In order to find out the best method for reuse of the alkali water,the alkali water was mixed with new reagent of NaOH,and the phosphorus recovery was carried out.The phosphorus was recovered as a sodium phosphate,and the recovery rate was almost the same even with the reuse of the alkali water.

Preparation of ultra-high pure scandium oxide with crude product from titanium white waste acid

Recovery of scandium from titanium white waste acid is an essential source of scandium.Simple and economical production of high purity scandium remains a challenge.A new extractant,N,N,N’,N’-tetracyclohexyl-diglycolamide(TCHDGA),was synthesized,and the separation performance of scandium from impurity metal ions(Ti,Mn,Ba,Fe,Al and Mg)was investigated,The effects of mixing time,acid concentration and temperature on the scandium extraction were considered.The extraction mechanism was studied by infrared spectroscopy and the Equimole Series Method.Under optimized conditions,the extractant shows a strong affinity to scandium in the nitric acid medium and high extraction separation factors between scandium and these impurity metal ions,A process for the purification of scandium was established.The crude product obtained from titanium white waste acid,95%purity scandium oxide,can be purified to 99.99%after only one step of extraction,scrubbing,and stripping:This technology is economical and straightforward and can realize the high-value recovery of scandium in the titanium white waste acid.

Effect of oxide interactions on chromium speciation transformation during simulated municipal solid waste incineration

Chromium released during municipal solid waste incineration(MSWI)is toxic and carcinogenic.The removal of chromium from simulated MSWI flue gas by four sorbents(CaO,bamboo charcoal(BC),powdered activated carbon(PAC),and Al_(2)O_(3))and the effects of four oxides(SiO_(2),Al_(2)O_(3),Fe_(2)O_(3),and CaO)on chromium speciation transformationwere investigated.The results showed that the removal rates of total Cr by the four sorbents were Al_(2)O_(3)<CaO<PAC<BC,while the removal rates of Cr(Ⅵ)by the four sorbents were Al_(2)O_(3)<PAC<BC<CaO.CaO had a strong oxidizing effect on Cr(Ⅲ),while BC and PAC had a better-reducing effect on Cr(Ⅵ).SiO_(2)was better for the reduction of Na_(2)CrO_(4)and K_(2)CrO_(4)above 1000℃due to its strong acidity,and the addition of CaO significantly inhibited the reduction of Cr(Ⅵ).MgCrO_(4)decomposed above 700℃to form MgCr_(2)O_(4),and the reaction between MgCrO_(4)and oxides also existed in the form of a more stable trivalent spinel.Furthermore,when investigating the effect of oxides on the oxidation of Cr(Ⅲ)in CrC_(l3),it was discovered that CaO promoted the conversion of Cr(Ⅲ)to Cr(Ⅵ),while the presence of chlorine caused chromium to exist in the form of Cr(V),and increasing the content of CaO and extending the heating time facilitated the oxidation of Cr(Ⅲ).In addition,silicate,aluminate,and ferrite were generated after the addition of SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3),which reduced the alkalinity of CaO and had an important role in inhibiting the oxidation of Cr(Ⅲ).The acidic oxides can not only promote the reduction of Cr(Ⅵ)but also have an inhibitory effect on the oxidation of Cr(Ⅲ)ascribed to alkali metals/alkaline earth metals,and the proportion of acidic oxides can be increased moderately to reduce the generation of harmful substances in the hazardous solid waste heat treatment.

废烟气脱硝催化剂中TiO_(2)资源化回收实验研究

采用高温碱浸和酸洗的方法对废选择性催化还原(SCR)脱硝催化剂进行处理,研究碱浸和酸洗对催化剂各组分的浸出效果,考察温度对催化剂浸出行为的影响规律。结果表明,碱浸温度的提高促进V和W的浸出,210℃时V和W的浸出率分别为82.38%和74.92%。经高温碱浸和酸洗处理后,Al、Ca、Na等杂质的最高浸出率均可达98%以上,回收TiO_(2)的纯度较高,可用于生产新催化剂。高温碱浸会破坏催化剂的结构,有利于后续HCl处理对杂质的去除,除杂效果优于直接酸洗处理。高温碱浸过程中会生成Na_(2)TiO_(3),经HCl反应并水解后会形成新的TiO_(2)颗粒,形成更多的小孔,比表面积增大。

扩散渗析回收琼脂生产废碱液工艺的响应面法优化

为了解决琼脂生产废碱液的资源化利用问题,利用扩散渗析装置对琼脂生产废碱液进行碱回收处理,并以料液流速、水/料流速比和温度为考察因素,以碱回收率和回收碱浓度为评价指标,进行3因素3水平的Box-Behnken中心组合实验设计,构建响应曲面模型,分析3个因素之间的交互作用对碱回收率和回收碱浓度的影响,确定扩散渗析法回收废碱液的最佳工艺条件。实验结果表明,当料液流速为0.75 L/(m^(2)·h)、水/料流速比为1.28、温度为65.5℃时,碱回收率达80%,获得的碱溶液浓度为1.14 mol/L,模型预测值与实验结果接近,模型可靠。这表明,扩散渗析能有效实现碱与有机物的分离,采用响应面法优化扩散渗析回收琼脂生产废碱液工艺是可行的。

废液晶玻璃再生制备低膨胀硼硅玻璃及其理化性能研究

基于废液晶玻璃的高值化再生利用,以废液晶玻璃作为主要原料,石英砂、硼酸、纯碱为辅助原料,制备了低膨胀硼硅玻璃。通过浮力法、压痕法、石英膨胀法和重量试验法,探究了废液晶玻璃和辅助原料(Na_(2)O和B_(2)O_(3))掺量对玻璃理化性能的影响。结果表明:随着废液晶玻璃掺量增加,玻璃密度、线热膨胀系数和耐酸质量损失增大,维氏硬度和耐碱质量损失减小;随着辅助原料中Na_(2)O含量增大,玻璃密度、线热膨胀系数、耐酸质量损失和耐碱质量损失增大,维氏硬度减小;随着辅助原料中B_(2)O_(3)含量增大,玻璃密度和维氏硬度减小,线热膨胀系数和耐酸耐碱质量损失增大;当废液晶玻璃、辅助原料中Na_(2)O和B_(2)O_(3)质量分数分别为60.00%、1.00%和14.72%时,玻璃维氏硬度最大、密度和线热膨胀系数最小,分别为7.1430 GPa、2.3097 g·cm^(-3)和3.5317×10^(-6)℃^(-1);当废液晶玻璃、辅助原料中Na2O和B2O3质量分数为60.00%、3.00%、9.72%时,玻璃耐酸质量损失最小,为0.6140 mg·cm^(-2);当废液晶玻璃、辅助原料中Na2O和B2O3质量分数为70.00%、2.00%、11.67%时,玻璃耐碱质量损失最小,为1.2140 mg·cm^(-2)。

Waste heat recovery and denitrification of flue gases from gas-fired boilers

A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfer techniques in a packed heat exchange tower with self-rotation and zero-pressure spraying, low temperature NO oxidation by ozone, and neutralization with an alkali solution. Operating data in a test project gave NOx in the exhaust flue gas of less than 30 mg/Nm3 with an ozone addition rate of 8 kg/h and spray water p H of 7.5–8, an average heat recovery of 3 MW, and an average heat supply of 7.2 MW.

响应曲面法优化废铂催化剂中难溶颗粒HCl-DCEA体系回收工艺

全溶解法回收废铂催化剂在实际生产过程中仍有难溶物沉积,造成二次污染及铂族资源浪费。本研究将难溶颗粒进行破碎细磨后,取300目左右粉体焙烧,然后将所得粉体在HCl-DCEA体系中进行浸出,考察反应时间、反应温度、液固比、盐酸浓度及DCEA浓度对铂浸出率的影响,并选择具有显著影响的液固比、盐酸浓度及DCEA浓度因素进行响应曲面优化试验。结果表明,对铂浸出率影响的显著顺序为DCEA浓度>液固比≈盐酸浓度;优化后的工艺条件为浸出时间2 h、浸出温度70℃、液固比6∶1、盐酸浓度2.35 mol/L、DCEA浓度0.09 mol/L,该条件下对废铂催化剂进行回收处理,总回收率达到99.64%。

载体酸洗对SCR脱硝催化剂性能影响研究

为实现废SCR催化剂中高含量TiO_(2)载体的绿色再利用,对碱浸渣体进行酸洗脱钠回收TiO_(2),后采用等体积共浸渍法制备V_(2)O_(5)-WO_(3)/TiO_(2)催化剂。考察了H_(2)SO_(4)洗涤浓度、焙烧温度对再合成SCR催化剂脱硝活性和物化性质的影响。研究表明:H_(2)SO_(4)能够有效脱除浸出渣中残留的碱金属和碱土金属,同时含有的SO_(4)^(2-)离子可发挥改性作用,增加催化剂的Bronsted酸性位点量,提高氧化还原性。与废催化剂相比,优化工艺下制备的SCR催化剂比表面积、氧化还原性及表面酸性位点量得到提升,脱硝活性明显恢复且低温脱硝段接近于商业催化剂水平。

酸性矿山废水中多种有价金属的高效分离

酸性矿山废水(AMD)中多种有价金属的高效分离回收,是重金属减排和资源化利用的关键。文章通过中和沉淀实验和静态吸附实验探究回收有价金属的最佳沉淀和吸附pH,成功开发了中和沉淀—离子交换—中和沉淀组合工艺,并应用于大宝山AMD的处理。结果表明,AMD在pH为3.00和9.80中和沉淀时,分别沉获64%的Fe_(2)O_(3)富铁渣和51%的Mn O富锰渣。采用离子交换树脂分别在pH 3.95和6.10条件下对AMD中的Cu和Zn进行吸附,得到质量浓度为Cu^(2+)11~26 g/L,Zn^(2+)10~20 g/L的两种解吸液。通过该组合工艺,AMD中的各金属Fe、Cu、Zn和Mn的回收率分别为:96%、81%、70%和60%,实现了有价金属的高效分离回收。若采用此工艺回收大宝山2000 m^(3)/d的AMD中的铜、锌、锰硫酸盐,每年的利润为119万元,经济效益非常显著。此处理工艺为酸性矿山废水的高效资源化利用提供了新路径。

扩散渗析法应用于琼脂加工废碱液回收的研究

琼脂生产企业产生大量的废碱液,具有氢氧化钠和有机物含量高的特点。运用扩散渗析法从琼脂加工废碱液中回收碱,考察扩散时间、料液流速、水/料流速比、温度等因素对碱回收的影响。结果表明,碱回收率随料液流速的增大而逐渐下降,随水/料流速比的增大而增加,随温度升高而增加。当进料液中碱含量为1.5 mg/L、料液流速1.0 L/(m^(2)·h)、水/料流速比1.2、温度65℃、扩散时间为1.5 h时,碱回收率74.25%,可获得浓度为1.12 mol/L的碱液。研究表明,扩散渗析能有效实现碱与有机物的分离,所回收的碱液可重新用于琼脂生产。

化学法预处理剩余污泥制备碳源的研究进展

剩余污泥(WAS)作为城市污水处理厂运行的必然产物,其产量也在逐年增加。WAS中含有大量的未稳定的有机物,针对此类有机物的资源化利用无疑会给污泥的减量化处置带来实际意义。WAS厌氧发酵产生的短链脂肪酸(SCFAs)被公认为优质碳源,但污泥水解是厌氧发酵的限速步骤,需要通过预处理方法促进污泥水解,从而提高SCFAs产量。本文综述了化学预处理剩余污泥中碱解预处理、氧化剂预处理和联合预处理等预处理方法研究进展,为以后以剩余污泥水解液为碳源的工艺提供技术指导。

剩余污泥有机质资源回收利用原位驱动晚期垃圾渗滤液深度脱氮——一种具有显著能源优势的创新生物技术

The sustainable recovery and utilization of sludge bioenergy within a circular economy context has drawn increasing attention,but there is currently a shortage of reliable technology.This study presents an innovative biotechnology based on free nitrous acid(FNA)to realize sustainable organics recovery from waste activated sludge(WAS)in-situ,driving efficient nitrogen removal from ammonia rich mature landfill leachate by integrating partial nitrification,fermentation,and denitrification process(PN/DN-F/DN).First,ammonia((1708.5±142.9)mg·L^(-1))in mature landfill leachate is oxidized to nitrite in the aerobic stage of a partial nitrification coupling denitrification(PN/DN)sequencing batch reactor(SBR),with nitrite accumulation ratio of 95.4%±2.5%.Then,intermediate effluent(NO_(2)^(-)-N=(1196.9±184.2)mg·L^(-1))of the PN/DN-SBR,along with concentrated WAS(volatile solids(VSs)=(15119.8±2484.2)mg·L^(-1)),is fed into an anoxic reactor for fermentation coupling denitrification process(F/DN).FNA,the protonated form of nitrite,degrades organics in the WAS to the soluble fraction by the biocidal effect,and the released organics are utilized by denitrifiers to drive NOx-reduction.An ultra-fast sludge reduction rate of 4.89 kg·m^(-3)·d^(-1) and nitrogen removal rate of 0.46 kg·m^(-3)·d^(-1) were realized in the process.Finally,F/DN-SBR effluent containing organics is refluxed to PN/DN-SBR for secondary denitrification in the post anoxic stage.After 175 d operation,an average of 19350.6 mg chemical oxygen demand organics were recovered per operational cycle,with 95.2%nitrogen removal and 53.4%sludge reduction.PN/DN-F/DN is of great significance for promoting a paradigm transformation from energy consumption to energy neutral,specifically,the total benefit in equivalent terms of energy was 291.8 kW·h·t^(-1) total solid.

铜冶炼污酸有价金属选择性回收药剂研究

铜冶炼污酸中富含铜、砷等有价金属,但传统处理方法存在回收率低、二次污染等问题。本文旨在开发一种新型有价金属选择性回收药剂,实现铜的高效回收和污酸资源化利用。通过实验确定了以吡咯为靶向试剂,硫化钠为沉淀剂的最佳复合药剂,并优化了投加比和制备方式。研究结果表明,该新型药剂对铜冶炼污酸中的铜离子具有显著的选择性回收效果,铜回收率可达99.2%,且铜渣品质符合铜精矿标准。该研究成果为铜冶炼污酸的资源化利用提供了新的思路和方法。

硫化砷渣协同处理铜冶炼烟尘浸出液回收铜

为充分回收铜冶炼过程产生的硫化砷渣和烟尘中的铜资源,降低对环境的影响,贯彻“以废治废”的理念,采用硫化分离技术,用铜冶炼生产过程产生的硫化砷渣沉淀富铜液回收铜冶炼固废中的铜资源。系统探究了沉淀过程中温度、硫化渣用量、反应时间对沉铜效率和硫化砷利用率的影响。结果表明:在反应温度80℃、每100 mL富铜液使用4.5 g硫化砷渣、反应时间3.5 h时具有最良好的铜沉淀效果,该条件下对应的铜沉淀率为88.92%,沉铜后的溶液中铜含量为0.36 mg/L,沉淀铜后所得铜渣中铜的质量分数为55.14%,砷的质量分数为3.18%,符合返回熔炼炉冶炼回收铜的要求;沉淀铜渣中的As主要来源于原料硫化砷渣,原料硫化砷渣中经氧化产生的少量As 2O 3在沉淀过程中不与稀硫酸反应,随着铜的沉淀一起沉到铜渣中。使用硫化砷渣沉淀铜可减少传统硫氢化钠沉淀铜过程中硫化氢气体的产生,全生产链为“以废治废”,且生产环境友好,结果可为铜冶炼企业提供参考。

间苯二甲酸装置废气碱洗塔设计

目前,某间苯二甲酸装置氧化料仓输送过程产生的废气均直接排放大气中,废气的有害成分主要为醋酸。废气中醋酸浓度远超《炼油与石油化学工业大气污染物排放标准》(DB 11/447—2015)的排放限值,即醋酸排放浓度应小于20 mg/m^(3)。根据废气排放特点,在分析和对比治理方法的基础上,最终选择碱液吸收法处理含醋酸废气。经碱洗塔水力学计算,对设备规格和材质等进行设计,使废气经处理后实现达标排放。