HCl-CuCl2-NaClO濕法浸取手機(jī)元器件中的鈀、金

丁江鈴1,3,張小平1,2,3*,朱亞茹1,3,張?zhí)煊?,3,劉競輝1,3(1.華南理工大學(xué)環(huán)境與能源學(xué)院,廣東 廣州 510006；2.工業(yè)聚集區(qū)污染控制與生態(tài)修復(fù)教育部重點實驗室,廣東 廣州 510006；3.廣東省固體廢物處理和回收利用重點實驗室,廣東 廣州 510006)

通過HCl-CuCl2-NaClO濕法浸出體系對手機(jī)元器件中金屬鈀(Pd)、金(Au)進(jìn)行浸出實驗,研究不同因素對于Pd、Au浸出率的影響.結(jié)果顯示,在2mol/L HCl、體積分?jǐn)?shù)5% NaClO、0.075mol/L CuCl2、固液比1%,反應(yīng)溫度60℃條件下,2h后Pd、Au浸出率均可達(dá)85%;結(jié)果表明,Cu2+、Cl-、溫度對于Pd的浸出率起很大作用,NaClO的加入可加快Pd浸出反應(yīng)達(dá)到平衡速率;NaClO、溫度對于Au的浸出率起關(guān)鍵作用,HCl、Cu2+的加入可促進(jìn)Au的浸出.因此,HCl-CuCl2-NaClO濕法浸出體系對于Pd、Au具有良好的浸出效果.

電子廢棄物；金；鈀；銅-氯體系；濕法浸出；手機(jī)

全球每年大約產(chǎn)生3500萬t的電子廢棄物,中國每年產(chǎn)生的電子廢棄物量超過300萬t[1].據(jù)估計,到2020、2030年,中國將產(chǎn)生1550,2840萬t電子廢棄物[2].新版《廢棄電器電子產(chǎn)品處理目錄》也于2016年3月1日起正式實施,在舊目錄的基礎(chǔ)上,將管理范圍擴(kuò)大至 14類,手機(jī)被納入其中.2013年中國廢舊手機(jī)產(chǎn)生量已達(dá)到7.99億部[3].廢舊手機(jī)中的貴金屬含量高于其他電子廢棄物,尤其是Ag和Pd的含量[2].平均每t廢舊手機(jī)中含 130kg Cu,3.5kg Ag,0.34kg Au,0.14kg Pd[4].

對于從手機(jī)線路板中回收金屬主要的研究方法有物理法、火法、濕法及生物法等[5-11].其中濕法回收電子廢棄物中金屬的研究最多.線路板金屬的研究集中于Cu、Au、Ag、Pd等[12-20].濕法回收貴金屬的研究方法有硫脲法,硫代硫酸鹽法,鹵化法等[4,16,21-23].

濕法浸取金屬方面常常使用氧化劑將其氧化,以離子或絡(luò)合物的形式進(jìn)入溶液中.一些研究已經(jīng)將O2、H2O2、Fe3+、Cl2等作為氧化劑運用到Cu、Fe、Ni、Au、Ag等的浸出實驗中[20,24-26].在氯化物介質(zhì)中,Cu2+也能夠作為氧化劑,對于普通金屬及貴金屬都有良好的氧化效果(銅-氯體系),一些研究將 Cu2+作為氧化劑運用到電子廢棄物中金屬浸取方面, Yazici等[12],Deveci等[26]在酸性條件下,加入NaCl,將Cu2+作為氧化劑,氧化浸出Cu、Ag等. Zhang等[20-21]運用CuSO4和NaCl溶液浸出線路板中的Ag、Pd,取得良好效果.但銅-氯體系對于Au的氧化浸出效果卻并不明顯,有研究將次氯酸鹽運用于礦物中 Au的浸出,實驗表明,次氯酸鹽對于 Au有良好的氧化浸出效果[19,27,29].

采用HCl-CuCl2-NaClO體系濕法浸出手機(jī)元器件粉末中的 Pd、Au,通過對銅-氯體系的改良,解決了Au浸出率低的問題,實現(xiàn)Pd、Au兩種貴金屬同時高效浸出.本實驗研究溫度、銅離子濃度、次氯酸鈉濃度、鹽酸濃度以及固液比(反應(yīng)時固體粉末質(zhì)量與液體體積比,g/mL)各因素對Pd、Au浸出效果的影響.以期為手機(jī)元器件中Pd、Au回收提供技術(shù)支持.

1 實驗材料與方法

1.1 實驗材料

實驗所用的材料來自佛山某資源利用有限公司提供的廢舊手機(jī),手工拆解手機(jī),取下電路板,利用熱風(fēng)槍將電路板表面的元器件吹落,將吹落的元器件收集后利用高速旋轉(zhuǎn)破碎機(jī)破碎至 60目以上(＜0.25mm)粉末.該手機(jī)元器件粉末即實驗所用的原材料.取0.5g元器件粉末采用HNO3-HCl-HF進(jìn)行消解.消解徹底后進(jìn)行趕酸稀釋,利用火焰原子吸收(AAS)測定金屬含量,進(jìn)行 6次重復(fù)實驗,金屬含量取其平均值,結(jié)果見表1.

表1 原材料中金屬含量Table 1 Metal contents of the sample

1.2 實驗方法

采用HCl、CuCl2、NaClO化學(xué)試劑(分析純),研究不同試劑濃度、不同溫度以及固液比對手機(jī)元器件粉末中Au、Pd浸出效果的影響,稱取3g粉末于500mL燒杯中,在不同反應(yīng)條件下進(jìn)行化學(xué)反應(yīng),HCl:1～2mol/L;CuCl2:0～0.125mol/L;NaClO: 5%～10%(體積比);固液比:1%～5%,置于不同溫度恒溫水浴鍋中,采用保鮮膜封口,在400r/min的數(shù)顯電動攪拌器下攪拌均勻.于不同反應(yīng)時間點采用20mL一次性注射器取樣、0.22μm水系過濾頭過濾后,采用火焰原子吸收(AAS)測定浸出液中金屬含量.每組實驗在同等實驗反應(yīng)條件下重復(fù)3次,取平均值.并根據(jù)原粉末中金屬含量計算得出浸出率.

2 結(jié)果與討論

2.1 CuCl2對Pd、Au浸出率的影響

在2mol/L HCl、5% NaClO,1%固液比,60℃反應(yīng)條件下,控制CuCl2的濃度,浸出率隨時間的變化見圖1.

從圖1可以看出,浸取金屬化學(xué)反應(yīng)進(jìn)行速率很快,對于Pd浸出,Cu2+濃度增加會提高Pd的浸出效率,但是基本上在半小時內(nèi)就達(dá)到平衡.在Cl-存在情況下,Cu2+作為氧化劑將金屬氧化為離子狀態(tài)進(jìn)入溶液中,Cu2+具有氧化性是由于它可作為Cl-的配位體.例如,在Cu2+和Cl-存在下金屬Cu首先溶解為亞銅(Cu+),隨后形成銅氯配合物(1≤n≤4)[12,26],溶液應(yīng)保證氯化物的濃度,以防止Cu+以CuCl沉淀形式存在.隨著Cl-濃度的不同,Cu2+也可能以 CuCln2-n的形式存在.增加Cl-濃度時,能夠降低普通金屬與貴金屬的反應(yīng)勢能(Cu、Fe、Au、Pd等)[30].Cu2+作為氧化劑將Cu、 Pd、Au氧化為、、Zhang等[28]研究發(fā)現(xiàn)Cu/Cu2+對于鈀的浸出效率有很大影響,當(dāng) Cu/Cu2+≥1.4時,主要跟元器件粉末中的Cu發(fā)生反應(yīng),生成CuCl沉淀,當(dāng)Cu/Cu2+≤0.95時,Pd被氧化,Pd的回收效率高達(dá)98%,Cu2+作為氧化劑將Cu、Pd、Au、Ag氧化,主要發(fā)生以下反應(yīng)[26]:

圖1 鈀和金的浸出率隨時間的變化([HCl]:2mol/L, [NaClO]:5%, 60℃, 1%固液比)Fig.1 Varations of palladium and gold leaching efficiencies with time ([HCl]:2mol/L, [NaClO]: 5%, 60℃, 1% S/L)

2.2 NaClO對Pd、Au浸出率的影響

在2mol/L HCl、0.075mol/L CuCl2,1%固液比,60℃反應(yīng)溫度下,控制 NaClO的量,浸出率隨時間的變化見圖2.

NaClO在有 HCl的情況下,可以水解為HClO、Cl2等,HClO的氧化性強于 ClO-.在有HClO、Cl2時,氧化性更強,加快 Pd的浸出速率.Au屬于高正電位金屬,溶解Au需要電極電位高的活性氧化劑.僅從標(biāo)準(zhǔn)電極電位的角度考慮,氯氣、次氯酸1.49V)的標(biāo)準(zhǔn)電極電位均小于 Au的氧化電位,不足以將Au氧化.但在有Cl-存在的溶液中,由于金離子與氯離子生成穩(wěn)定的絡(luò)離子,,使其活度降低,從而使 Au的溶解電位大幅度降低[29].Cl--Cl2體系對于 Au的氧化浸出具有很好的效果,氯化物跟 Au的反應(yīng)速率比氰化物更快,同時不會在金的表面產(chǎn)生鈍化[27].當(dāng)pH≤2,溶液中存在Cl2、Cl-時,容易將Au氧化為.在氯化物溶液中 Au的溶解機(jī)理為:首先形成AuCl,進(jìn)一步跟Cl-結(jié)合為,最終被氧化為.主要發(fā)生的反應(yīng)為:

圖2 鈀和金的浸出率隨時間的變化([HCl]:2mol/L, [CuCl2]:0.075mol/L, 60℃, 1%固液比)Fig.2 Varations of palladium and gold leaching efficiencies with time ([HCl]:2mol/L, [CuCl2]:0.075mol/L, 60℃, 1% S/L)

2.3 HCl對Pd、Au浸出率的影響

在 0.075mol/L CuCl2、5%NaClO,1%固液比,60℃反應(yīng)條件下,控制 HCl的量,浸出率隨時間的變化見圖3.

圖3 鈀和金的浸出率隨時間的變化Fig.3 Varations of palladium and gold leachingefficiencies with time

HCl濃度的增加會促進(jìn)Pd、Au的溶出,在大氣壓條件下,高濃度氯化物溶液可以增加質(zhì)子活性,促進(jìn)穩(wěn)定的金屬氯化復(fù)合物的形成.增加氯化物的濃度導(dǎo)致普通金屬與貴金屬(例如 Cu,Au, Pd,Ag)的氧化還原電位的降低[23].一些金屬氯化物添加Cl-后氧還原電位的變化見表2.

表2 金屬氯化物的氧化還原電位Table 2 Potential of some metal cholride complexes[31]

2.4 溫度對Pd、Au浸出率的影響

在 2mol/L HCl、5% NaClO、0.075mol/L CuCl2,1%固液比,控制反應(yīng)溫度,浸出率隨時間的變化見圖4.

圖4 鈀和金的浸出率隨時間的變化Fig.4 Varations of palladium and gold leaching efficiencies with time

從圖4可以看出,溫度對于Pd、Au的浸出率及反應(yīng)速度都有很大的影響.溫度的升高可以提高金屬的浸出率和反應(yīng)速率,主要是因為金屬的氧化浸出是吸熱反應(yīng),增加反應(yīng)溫度可以降低氧化還原電位,促進(jìn) Pd、Au氧化為PdCl42-、AuCl4-.但同時過高的溫度會造成HCl、NaClO的揮發(fā), 60℃與80℃時Pd、Au的浸出率并沒有相差很多,有可能是HCl、NaClO揮發(fā)損失所造成.

2.5 固液比對Pd、Au、Ag浸出率的影響

不同固液比(1%～5%)在反應(yīng) 4h后的金屬浸出率見圖5,反應(yīng)條件為:60℃,2mol/L HCl、0.075mol/L CuCl2、5% NaClO.從圖中可以看出該體系對于金屬Ag也有良好的浸出效率,即使在較高的固液比下,Ag也有良好的浸出率.在5%固液比條件下,Pd的浸出率仍有80%.但Au隨固液比的增加,浸出率下降很快,這是因為Au的氧化電位在這些金屬中最高,最難溶出,當(dāng)溶液中的氧化性不夠時,Au的浸出率最先出現(xiàn)下降.

圖5 不同固液比金屬浸出率Fig.5 The effect of solid/liquid ratio on the extraction of metals over 240min

3 結(jié)論

3.1 HCl-CuCl2-NaClO體系對于Pd的浸出率主要是由Cu2+、Cl-的濃度決定,NaClO的加入可加快反應(yīng)的進(jìn)行,溫度的升高同樣可促進(jìn)反應(yīng)的進(jìn)行,在 2mol/L HCl、0.075mol/L CuCl2、5%NaClO、1%固液比、80℃條件下5h后可實現(xiàn)93%的浸出率.

3.2 銅-氯體系中加入 NaClO可大大提高 Au的溶出,在一定濃度HCl存在時,金的浸出率主要與NaClO、溫度有關(guān).

3.3 該體系不僅對于Pd、Au的浸出效果好,同時對于Cu、Ag的浸出率也很高,在2mol/L HCl、0.075mol/L CuCl2、5%NaClO、60℃條件下,即使固液比為5%時,4h后也可實現(xiàn)Cu、Ag 90%以上的浸出率.

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Extraction of Pd,Au from Phone components in HCl-CuCl2-NaClO solutions.

DING Jiang-ling1,3, ZHANG Xiao-ping1,2,3*, ZHU Ya-ru1,3, ZHANG Tian-yu1,3, LIU Jing-hui1,3(1.School of Environment and Energy, South China University of Technology, Guangzhou 510006, China；2.Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China；3.Guangdong Environmental Protection Key Laboratory of Solid Waste Treatment and Recycling, Guangzhou 510006, China). China Environmental Science, 2016,36(12)：3711～3716

A novel hydrometallurgical process for recovery of palladium and gold from phone components in HCl-CuCl2-NaClO leaching system was offered, different factors of Pd, Au leaching process were investigated. The results of experiment indicated that, on the condition of 2mol/L HCl, 5% NaClO, 0.075mol/L CuCl2at 333K for 2h with a solid/liquid ratio of 1/100, over 85% of Pd and Au was leached. Cu2+, Cl-, the temperature for the Pd leaching rates played a significant role. NaClO was added to solutions could accelerate the Pd leaching reaction rates; NaClO, the temperature for the Au leaching rates had a significant influence. The additions of HCl, Cu2+to promotes Au leaching. Therefore, HCl-CuCl2-NaClO leaching system for Pd, Au leaching have a positive effect.

waste electrical and electronic equipment；gold；palladium；cupric-chloride leaching；hydrometallugry；mobile phone

X705

A

1000-6923(2016)12-3711-06

丁江鈴(1992-),女,江西鷹潭人,華南理工大學(xué)碩士研究生,主要從事電子廢棄物資源化處理與處置方面的研究.

2016-06-02

國家自然科學(xué)基金(21377041);廣東省科技計劃項目(2013B021300022);亞熱帶建筑科學(xué)基金會國家重點實驗室(2013KB28)

* 責(zé)任作者, 教授, xpzhang@scut.edu.cn