纖維素是天然可再生高分子材料，且無毒、可降解和價格低廉 因為化石能源短缺和化石燃料環(huán)境污染，開發(fā)和應(yīng)用纖維素可再生材料極為重要 纖維素的結(jié)構(gòu)中含有大量的羥基，具有一定的吸附能力但是吸附容量很低 對纖維素進(jìn)行化學(xué)改性引入新的官能團，可顯著提高其吸附性能[1~4] 將纖維素的尺寸降低到納米級，也稱為納米纖維素(NC)，可增大其長徑比和比表面積，使其吸附性能提高[5,6] 對纖維素進(jìn)行化學(xué)或物理處理，可得到納米纖維素(至少有一維尺寸達(dá)到納米級) 與傳統(tǒng)的纖維素相比，納米纖維素具有高強度、高比表面積、高楊氏模量和長徑比大等性能，是目前纖維素科學(xué)和技術(shù)領(lǐng)域中最具發(fā)展?jié)摿Φ牟牧现籟7,8] 目前對纖維素吸附劑的研究比較多，但是對納米纖維素吸附劑的研究比較少[9]

制備納米纖維素的常用方法，有機械法、酸解法和酶解法 其中機械法能耗大，成本高；酸水解法對設(shè)備的要求苛刻，殘留物難以回收和后處理；酶解法的效率不高，反應(yīng)條件尚需優(yōu)化 因此開發(fā)綠色高效的納米纖維素制備方法，是該領(lǐng)域的研究熱點

離子液體是由有機陽離子和無機或有機陰離子構(gòu)成的液態(tài)有機鹽類物質(zhì)，有不易揮發(fā)、不可燃、性質(zhì)穩(wěn)定、可循環(huán)利用及無污染等優(yōu)點，是一種“綠色”化學(xué)溶劑 自2002年Swatloski等[10]發(fā)現(xiàn)離子液體可溶解纖維素以來，離子液體憑借其優(yōu)異的性能在纖維素的資源化轉(zhuǎn)化與利用方面表現(xiàn)出巨大的潛力 使用酸性離子液體可將纖維素水解成纖維素單鏈用于制備納米纖維素，備受關(guān)注[11] 鑒于此，本文使用離子液體作為溶劑和催化劑，對纖維素進(jìn)行溶脹和水解制備納米纖維素；在纖維素水解的同時對其進(jìn)行接枝共聚改性制備納米纖維素吸附劑，并研究其吸附性能

1 實驗方法1.1 實驗用原料

脫脂棉纖維素；離子液體為1-丁基-3-甲基咪唑硫酸氫鹽([Bmim]HSO4)(熔點為28℃，純度99%)；丙烯酸、過硫酸鉀、丙酰胺和無水乙醇，純度99%以上

1.2 納米纖維素和納米纖維吸附劑(AA/AM-g-NC)的制備

NC的制備：將1 g脫脂棉纖維和20 g離子液體 [Bmim]HSO4加入250 mL三口燒瓶中，將三口燒瓶置于100℃油浴鍋中加熱且均勻攪拌以使脫脂棉纖維完全溶脹、分散并水解，反應(yīng)2 h后將纖維素溶液在溫水浴中超聲30 min，然后用無水乙醇和蒸餾水反復(fù)離心(2000 r/min)洗滌至中性 將洗滌后的纖維素均勻分散在超純水(濃度在1%左右)中，放入高壓細(xì)胞均質(zhì)機中使其進(jìn)一步超微細(xì)化 為了防止高壓過程中的溫度過高，實驗在5℃的冷卻水循環(huán)機中進(jìn)行 高壓均質(zhì)后，取上清液分析備用

AA/AM-g-NC的制備：將1 g脫脂棉纖維和適量的離子液體1-丁基-3-甲基咪唑硫酸氫鹽([Bmim]HSO4)加入250 mL三口燒瓶中，將三口燒瓶置于100℃油浴鍋中加熱且均勻攪拌以使脫脂棉纖維完全溶脹并分散；將分散后的纖維素離子液體溶液的溫度降至40~50℃，然后在N2保護(hù)下按比例加入一定質(zhì)量的引發(fā)劑過硫酸鉀，繼續(xù)通N2并在勻速攪拌下加入一定比例的單體丙烯酰胺(AM)、80%中和度的丙烯酸(AA)和交聯(lián)劑N，N-亞甲基雙丙烯酰胺，繼續(xù)反應(yīng)3 h 反應(yīng)結(jié)束后在離心機中用蒸餾水和無水乙醇或丙酮反復(fù)離心洗滌，并用丙酮作為溶劑索氏抽提去除均聚物；隨后將抽提后的纖維素基接枝共聚物(記為AA/AM-g-Ce)均勻分散在超純水中，形成均勻的水相分散液(濃度在1%~2%左右) 將分散液放入高壓細(xì)胞均質(zhì)機中，利用勻質(zhì)機內(nèi)的勻質(zhì)閥突然失壓形成的空穴效應(yīng)和高速沖擊，使懸浮液進(jìn)一步超微細(xì)化 為了防止高壓過程中溫度過高，實驗在5℃的冷卻水循環(huán)機中進(jìn)行 高壓均質(zhì)后即可得到納米纖維素基接枝共聚物膠體溶液，將其冷凍干燥后得到納米纖維素吸附劑，記為AA/AM-g-NC

1.3 產(chǎn)物的表征

用超高分辨率場發(fā)射掃描電鏡(XL-30，Philips-FEI公司)和場發(fā)射透射電子顯微鏡(Tecnai G2 F20對S-TWIN 200kV，Philips-FEI公司)分析產(chǎn)物的微觀形貌和尺寸；將干燥的Ce、NC、AA/AM-g-NC分別與KBr按一定比例混合，在瑪瑙研缽中精細(xì)研磨后擠壓成圓盤狀 在分析前，將其置于70℃烤箱中干燥10 min 用傅里葉變換紅外光譜儀(Nicolet is5，賽默飛公司)分析產(chǎn)物的官能團，設(shè)定掃描范圍為400~4000 cm -1；用元素分析儀(2400系列II型CHNS/O)定量測定NC、AA/AM-g-NC樣品中C、H、N和O各元素的含量；使用X射線粉末光衍射儀(X'Pert Pro MPD)對樣品進(jìn)行掃描分析；用X-射線光電子能譜(Thermo Scientific ESCALAB 250 X，Thermo Fisher Scientific 公司)測定樣品表面的化學(xué)組分

1.4 納米纖維素吸附劑吸附性能的表征

以亞甲基藍(lán)溶液為吸附質(zhì)，用靜態(tài)吸附試驗測定AA/AM -g-NC的吸附性能 將50 mL濃度為20 mg/L的亞甲基藍(lán)溶液放入錐形瓶中，投加0.02 g吸附劑AA/AM-g-NC后置于恒溫振蕩床中在一定溫度和轉(zhuǎn)速條件下震蕩一段時間 反應(yīng)結(jié)束后取適量的上清液用紫外可見分光光度計測定亞甲基藍(lán)吸光度(λ=664 nm)，用亞甲基藍(lán)的工作曲線計算其濃度并計算吸附劑的吸附容量

去除率為：

η=Ce-C0Ce×100%

(1)

平衡吸附容量為：

Qe=Ce-C0X×V

(2)

式中Ce為吸附前亞甲基藍(lán)的質(zhì)量濃度(mg/L)，C0為吸附后亞甲基藍(lán)的質(zhì)量濃度(mg/L)，V為亞甲基藍(lán)溶液的體積(L)，X為AA/AM-g-NC的用量(g)

2 實驗結(jié)果和分析2.1 納米纖維素吸附劑的形貌和組成

納米纖維素(NC)及納米纖維素吸附劑AA/AM-g-NC的表面形貌(圖1) 從圖1可以看出，脫脂棉經(jīng)離子液體[Bmim]HSO4水解和高壓均質(zhì)處理后尺寸大大減小(圖1a)，纖維素呈納米纖絲狀且相互交聯(lián)成網(wǎng)狀結(jié)構(gòu)(圖1b) 其原因是，纖維素經(jīng)酸性離子液體水解并輔助高壓均質(zhì)處理后尺寸減小，且在水解過程中進(jìn)行了接枝共聚和交聯(lián)改性，表面的羥基及官能團之間的氫鍵作用使納米纖絲相互纏繞 10 μm納米纖維素和吸附劑的透射電鏡TEM照片，如圖2所示 從圖2a可見，納米纖維素NC大都呈短棒狀，部分呈纖絲狀；而納米纖維素吸附劑則由纖絲交聯(lián)成網(wǎng)狀結(jié)構(gòu)，與SEM觀察的結(jié)果一致

圖1



圖1NC和AA/AM-g-NC的SEM 照片

Fig.1SEM images of NC (a) and AA/AM-g-NC (b)

圖2



圖2NC及AA/AM-g-NC的TEM像

Fig.2TEM images of NC (a) and AA/AM-g-NC (b)

脫脂棉纖維素Ce、納米纖維素NC及其接枝共聚物AA/AM-g-NC的紅外光譜，如圖3所示 從圖3可見，NC及其接枝產(chǎn)物AA/AM-g-NC都保留了纖維素的特征吸收峰，AA/AM-g-NC還在1730 cm-1處出現(xiàn)C=O的伸縮振動峰[12]，且在3300~3400 cm-1范圍峰變寬；1630 cm-1處的峰變尖銳，分別是 N-H 鍵的拉伸和彎曲振動所致[13]；此外，AA/AM-g-NC的O-H吸收峰發(fā)生了明顯的藍(lán)移現(xiàn)象，由Ce的3354 cm-1變成了3416 cm-1；以上結(jié)果表明，單體丙烯酸和丙烯酰胺成功地接枝在納米纖維素上

圖3



圖3Ce、NC和AA/AM-g-NC的紅外光譜

Fig.3FTIR of Ce, NC and AA/AM-g-NC

纖維素、NC及其吸附劑AA/AM-g-NC的XRD譜圖，如圖4所示 從圖4可以看出，NC和AA/AM-g-NC的晶型結(jié)構(gòu)與纖維素晶型相同，在2θ=14.8°，16.5°，22.6°和34.5°的峰分別對應(yīng)纖維素I型的4個晶面，表明離子液體處理、改性及后續(xù)的高壓均質(zhì)處理并沒有破壞納米纖維素的晶面；其結(jié)晶度由纖維素的67.1%提高到75.1%，因為在纖維素水解及改性過程中纖維素的無定形區(qū)被破壞并水解，使NC及納米纖維素吸附劑的結(jié)晶度提高[14]

圖4



圖4NC和AA/AM-g-NC的XRD譜圖

Fig.4XRD patterns of NC and AA/AM-g-NC

納米纖維素和吸附劑表面元素的XPS圖譜，如圖5和圖6所示 圖5表明，接枝改性后的納米纖維素吸附劑表面的元素除C、H、O外，還有N元素 由N1s的高分辨XPS圖譜可知，其特征峰的結(jié)合能為399.6 eV，表明N以氨基(-NH2)的形式存在

圖5



圖5納米纖維素NC和AA/AM -g-NC的XPS圖譜以及N1s的高分辨圖譜

Fig.5XPS survey spectra of NC (a) and AA/AM-g-NC (b) and XPS survey scan of N1s core level (b inserted)

圖6



圖6NC和AA/AM-g-NC處理后C1s、N1s和O1s的XPS圖譜

Fig.6XPS survey of C1s, N1s and O1s of NC and AA/AM-g-NC

圖6給出了 C1s、O1s及N1s的高分辨圖譜 NC及吸附劑上的C有三種類型[15]：一種是與C或H連接的C，即C-(C，H)，其電子結(jié)合能為284.6 eV；第二種為與O或N連接的C，即C-O或C-N，其電子結(jié)合能為286 eV；第三種是連接兩個O的C，即O-C-O或C=O，其電子結(jié)合能為287.7 eV 在O1s的高分辨圖譜中，NC中的O主要來自C-O單鍵，即HO-C和C-O-C，其結(jié)合能為532.6 eV；而吸附劑AA/AM-g-NC中的O有兩種類型：1) C-O單鍵，結(jié)合能為532.6 eV；2) C=O雙鍵，結(jié)合能為531.2 eV，主要來自丙烯酸及丙烯酰胺的酯基 吸附劑AA/AM-g-NC表面的N元素，主要來源于接枝的單體丙烯酰胺中的氨基(-NH2)，其結(jié)合能為399.6 eV XPS結(jié)果表明，吸附劑表面有羧基及氨基基團

為了進(jìn)一步證明吸附劑上官能團的存在，對NC及吸附劑AA/AM-g-NC進(jìn)行元素分析，結(jié)果列于表1 表1中的數(shù)據(jù)表明，納米纖維素接枝后元素的含量發(fā)生了較大的變化，C、N元素含量的提高及O元素含量的降低證明氨基(-NH3)、羧基(-COOH)已經(jīng)成功地接枝在納米纖維素上

Table 1

表1

表1NC和 AA/AM -g-NC元素含量

Table 1Element content of NC and AA/AM-g-NC

Sample	O/%	C/%	H/%	N/%
NC	51.24	42.65	6.02	0.37
AA/AM-g-NC	46.21	44.07	6.09	3.13

表2列出了Ce、NC和AA/AM-g-NC的比表面積、孔容及平均孔徑 由表2中數(shù)據(jù)可知，Ce的比表面積僅有3.39 m2/g，平均孔徑為6.047 nm.與水解均質(zhì)后的NC和接枝改性后的AA/AM-g-NC相比，BET比表面積分別升高至13.04 m2/g和12.95 m2/g，平均孔徑分別為4.01 nm和5.834 nm 這表明，在纖維素變成NC及AA/AM-g-NC過程中纖維素的尺寸減小，比表面積增大 較大的比表面積，為吸附污染物提供了較高的吸附潛能

Table 2

表2

表2Ce、NC和AA/AM-g-NC的吸附參數(shù)

Table 2Adsorption parameters of Ce, NC and AA/AM-g-NC

Sample	Parameters of pore structure
	Surface area/m2·g-1	Pore volume /cm3·g-1	Average pore size /nm
Ce	3.390	0.0036	6.047
NC	13.04	0.013	4.010
AA/AM-g-NC	12.95	0.019	5.834

2.2 納米纖維素吸附劑AA/AM -g-NC的吸附性能2.2.1 AA/AM-g-NC對亞甲基藍(lán)的吸附性能

AA/AM-g-NC對亞甲基藍(lán)的吸附容量，如圖7所示 從圖7可以看出，改性后的納米纖維素對亞甲基藍(lán)的吸附容量大大增加，從未改性的14.6增加到43.96 mg/g 與Ce、AA/AM-g-Ce和NC相比，AA/AM-g-NC吸附量的大幅度提高歸因于其表面的官能團和比表面積的增加 接枝共聚改性賦予納米纖維素表面許多羧基及氨基官能團，從而增大了對亞甲基藍(lán)的吸附性能；另一方面，納米纖維素吸附劑比AA/AM-g-Ce大的比表面積能提供更多的吸附位點，有利于吸附劑對亞甲基藍(lán)的吸附

圖7



圖7Ce、NC、AA/AM-g-Ce和AA/AM-g-NC對亞甲基藍(lán)的去除率和吸附容量對比

Fig.7Comparison of remove rate and adsorption capacity of methylene blue on Ce, NC, AA/AM-g-Ce and AA/AM-g-NC. Adsorption conditions: pH,10; MB initial concentration, 20 mg/L; adsorption time, 2 h; adsorption temperature, room temperature

此外，與文獻(xiàn)中的納米纖維素吸附劑相比(表3)，改性后的AA/AM-g-NC對亞甲基藍(lán)的吸附性能也表現(xiàn)出一定的優(yōu)勢

Table 3

表3

表3與文獻(xiàn)中納米纖維素吸附劑對亞甲基藍(lán)吸附性能的比較

Table 3Comparison of adsorption performance towards methyl blue between AA/AM-g-NC and other nanocellulse adsorbent reported

Adsorbent	Solute	C0/mg·L-1	qe(exp)/mg·L-1	Ref.
NCC(T=35℃)		4.80	2.9	[16]
		9.60	4.9
		14.39	6.6
NCC(T=45℃)	MB	4.80	2.9
		9.60	5.4
		14.39	6.9
NCC(T=55℃)		4.80	2.9
		9.60	5.4
		14.39	6.7
		100	10.41	[17]
		200	17.24
NCC alginate hydrogel beads	MB	400	35.28
		600	50.29
		800	72.84
Cellulose nanowhiskers-based polyurethane foam	MB	50	43.5	[18]

2.2.2 溶液pH值對吸附性能的影響

以接枝改性后的納米纖維素AA/AM-g-NC為吸附劑，研究吸附劑對20 mg/L亞甲基藍(lán)的吸附性能 圖8給出了吸附過程中pH值對吸附劑吸附性能的影響 由圖8可見，在堿性條件下納米纖維素吸附劑具有更優(yōu)異的吸附性能 其原因是，在堿性條件下溶液中H+濃度的降低降低了與亞甲基藍(lán)陽離子的競爭吸附，從而提高了吸附劑對亞甲基藍(lán)的去除率和吸附容量

圖8



圖8pH值對AA/AM-g-NC吸附性能的影響

Fig.8Effect of pH on the adsorption properties of AA/AM-g-NC. Adsorption conditions: MB initial con-centration, 20 mg/L; adsorption time, 2 h; adsorption temperature, room temperature

2.2.3 Langmuir和Freundlich吸附等溫式 使用Langmuir和Freundlich吸附等溫式[19]

Ceqe=1b?Q0+CeQ0

(3)

lgqe=lgK+1nlgCe

(4)

研究了AA/AM-g-NC的吸附行為，擬合結(jié)果如圖9和表4所示 式中qe為吸附劑的平衡吸附容量(mg/g)，Ce為亞甲基藍(lán)的平衡濃度(mg/L)，Q0為吸附劑的飽和吸附容量(mg/g)，b為Langmuir常數(shù)(L/mg)，K和n為Freundlich參數(shù)

圖9



圖9Langmuir及Freundlich方程擬合圖

Fig.9Langumuir (a) and Freundlich (b) equation fitting

Table 4

表4

表4擬合的Langmuir和Freundlich參數(shù)

Table 4Calculated parameters for the Langmuir and Freundlich model

Temperature/K	Langmuir parameters			Freundlich parameters
	Q0/mg·g-1	b/L·mg-1	R2	K	1/n	R2
303	35.84	0.982	0.996	16.87	0.311	0.981
313	34.36	0.915	0.995	16.15	0.296	0.990
323	32.57	0.829	0.988	15.25	0.284	0.981

可以看出，Langmuir吸附等溫模型在三個溫度的相關(guān)系數(shù)R2均高于Freundlich吸附等溫模型，且根據(jù)Langmuir等溫吸附模型計算出的最大吸附量Q0與實驗測得的最大吸附容量qe的一致性很好 這表明，納米纖維素吸附劑對亞甲基藍(lán)的吸附符合Langmuir等溫吸附模型，對亞甲基藍(lán)在吸附劑表面發(fā)生的是單分子層吸附

2.2.4 吸附熱力學(xué) 可根據(jù)吉布斯自由能(?G)、焓變化(?H)和熵變化(?S)研究吸附劑AA/AM-g-NC對亞甲基藍(lán)的吸附熱力學(xué) ?G、?H和?S分別為[20~22]

ΔG=-RTlnb

(5)

lnb=ΔSR-ΔHRT

(6)

ΔS=(ΔH-ΔG)/T

(7)

式中，b為Langmuir參數(shù)(L/mol)，ΔH為焓變(kJ/mol)，R為氣體參數(shù)(8.314 J/(mol·K))，T為吸附溫度(K)，ΔG為自由能的變化(kJ/mol)，ΔS為熵變(kJ/(mol·K))

使用準(zhǔn)一級動力學(xué)方程

lg(qe-qt)=lgqe-k1t

(8)

和準(zhǔn)二級動力學(xué)方程

tqt=1k2qe2+tqe

(9)

計算出的熱力學(xué)參數(shù)，列于表5 式中t為吸附時間(min)，qe為AA/AM-g-NC的平衡吸附容量(mg/g)，qt為AA/AM-g-NC在t時刻的吸附容量(mg/g)，k1為一級吸附速率常數(shù)(min-1)；k2為二級反應(yīng)速率常數(shù)(g·mg-1·min-1) 由表5中的數(shù)據(jù)可知，?H<0說明AA/AM-g-NC對亞甲基藍(lán)的吸附過程為放熱過程，升溫不利于促進(jìn)AA/AM-g-NC對亞甲基藍(lán)的吸附；?G<0說明AA/AM-g-NC對亞甲基藍(lán)的吸附是在自發(fā)有利的條件下進(jìn)行的；而?S<0說明整個吸附過程為熵減少的過程[23]

Table 5

表5

表5熱力學(xué)參數(shù)

Table 5Thermodynamic parameters

Temperature/K	△G/kJ·mol-1	△S/J·(mol·K)-1	△H/kJ·mol-1
303	-0.0459	-0.0225	-6.876
313	-0.232	-0.0212
323	-0.505	-0.0197

2.2.5 吸附動力學(xué)

為了研究AA/AM-g-NC對亞甲基藍(lán)的吸附機理，采用準(zhǔn)一級、準(zhǔn)二級和粒子內(nèi)反應(yīng)擴散方程[24~26]分別對303 K下的吸附實驗數(shù)據(jù)進(jìn)行動力學(xué)擬合，擬合公式為式9和擴散方程

qt=KTt1/2+C

(10)

式中，t為吸附時間(min)，qt為AA/AM-g-NC在t時刻的吸附容量(mg/g)，KT為顆粒內(nèi)擴散速率常數(shù)(mg/(g·min1/2))，C為常數(shù) 相關(guān)的擬合結(jié)果如圖10、11和表6所示 根據(jù)擬合結(jié)果分析，AA/AM-g-NC對亞甲基藍(lán)溶液的吸附過程更符合準(zhǔn)二級動力學(xué)模型(R2值判斷)，且準(zhǔn)二級動力學(xué)模型的理論平衡吸附量也更接近實驗值，說明AA/AM-g-NC對亞甲基藍(lán)的吸附主要以化學(xué)吸附為主[27] 顆粒內(nèi)擴程的擬合圖(圖11)呈三段式分布，且不經(jīng)過原點，說明AA/AM-g-NC吸附亞甲基藍(lán)的過程不僅由顆粒內(nèi)擴散控制，還受表面擴散控制

圖10



圖10準(zhǔn)一級動力學(xué)和準(zhǔn)二級動力學(xué)擬合曲線

Fig.10Fitting curves of Pseudo-first-order (a) and Pseudo-second-order (b)

圖11



圖11顆粒內(nèi)擴散反應(yīng)方程曲線

Fig.11Intraparticle diffusion equation curve

Table 6

表6

表6吸附過程的動力學(xué)參數(shù)

Table 6Kinetic parameters of adsorption process

Pseudo-first-order kinetic model			Pseudo-second-order kinetic model
k1	qe	R2	k2	qe	R2
0.030	56.02	0.935	0.0012	48.92	0.999

3 結(jié)論

(1) 以脫脂棉纖維素為原料、以丙烯酸AA和丙烯酰胺AM為接枝單體，在離子液體[Bmim]HSO4中對纖維素進(jìn)行水解及接枝改性，然后對其進(jìn)行高壓均質(zhì)處理，可制備出納米纖維素吸附劑AA/AM-g-NC 對脫脂棉進(jìn)行離子液體輔助高壓均質(zhì)處理后得到纖絲網(wǎng)狀結(jié)構(gòu)的納米纖維素吸附劑AA/AM-g-NC，其表面接有AM及AA的官能團，纖維素的晶型沒有改變，結(jié)晶度有所提高

(2) 納米纖維素吸附劑AA/AM-g-NC對亞甲基藍(lán)的吸附性能受pH值的影響，堿性條件有利于吸附劑的吸附；對亞甲基藍(lán)的吸附符合Langmuir吸附等溫式，為單分子層吸附；吸附過程為放熱反應(yīng)，升溫不利于AA/AM-g-NC對亞甲基藍(lán)的吸附 吸附在自發(fā)有利的條件下進(jìn)行，吸附過程為固/液相界面的分子運動趨于穩(wěn)定的熵減少過程；吸附過程符合準(zhǔn)二級動力學(xué)模型 對亞甲基藍(lán)的吸附，受控于顆粒內(nèi)擴散和表面擴散

參考文獻(xiàn)

View Option 原文順序文獻(xiàn)年度倒序文中引用次數(shù)倒序被引期刊影響因子

[1]

O'Connell D W, Birkinshaw C, O'Dwyer T F.

Heavy metal adsorbents prepared from the modification of cellulose: A review

[J]. Bioresour. Technol., 2008, 99: 6709

DOIURLPMID [本文引用: 1] " />

We report here initial results that demonstrate that cellulose can be dissolved without activation or pretreatment in, and regenerated from, 1-butyl-3-methylimidazolium chloride and other hydrophilic ionic liquids. This may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this important bioresource.

[11]

Lu Y, Sun Q F, Yu H P, et al.

Dissolution and regeneration of cellulose and development in processing cellulose-based materials with ionic liquids

[J].Chin. J. Org. Chem., 2010, 30: 1593

[本文引用: 1]

(盧蕓, 孫慶豐, 于海鵬等.

離子液體中的纖維素溶解、再生及材料制備研究進(jìn)展

[J]. 有機化學(xué), 2010, 30: 1593)

[本文引用: 1]

[12]

Qiu J, Wang Z Y, Sun Q, et al.

Effect of surface modification and hybridization of uhmwpe fibers on performance of their composites with epoxy resin

[J].Chin. J. Mater. Res., 2015, 29: 807

[本文引用: 1]

(邱軍, 王增義, 孫茜等.

表面改性和混雜對超高分子量聚乙烯纖維/環(huán)氧樹脂復(fù)合材料性能的影響

[J]. 材料研究學(xué)報, 2015, 29: 807)

[本文引用: 1]

[13]

Su X Y, Bai B, Ding C X, et al.

Preparation and water absorption/retention properties of coconut husk powders/ poly (acrylic acid-co-acryl amide) hybrid superabsorbent

[J].Mater. Rev., 2015, 29(6): 54

[本文引用: 1]

(蘇小育, 白波, 丁晨旭等.

椰糠粉/聚丙烯酸-丙烯酰胺復(fù)合吸水材料的制備及其吸保水性能

[J]. 材料導(dǎo)報, 2015, 29(6): 54)

[本文引用: 1]

[14]

Wang Y H, Wei X Y, Li J H, et al.

Homogeneous isolation of nanocellulose from cotton cellulose by high pressure homogenization

[J]. J. Mater. Sci. Chem. Eng., 2016, 1: 49

[本文引用: 1]

[15]

Zafeiropoulos N E, Vickers P E, Baillie C A, et al.

An experimental investigation of modified and unmodified flax fibres with XPS, ToF-SIMS and ATR-FTIR

[J]. J. Mater. Sci., 2003, 38: 3903

[本文引用: 1]

[16]

Samiey B, Tehrani A D.

Study of adsorption of Janus Green B and methylene blue on nanocrystalline cellulose

[J]. J. Chin. Chem. Soc., 2015, 62: 149

[本文引用: 1]

[17]

Mohammed N, Grishkewich N, Berry R M, et al.

Cellulose nanocrystal-alginate hydrogel beads as novel adsorbents for organic dyes in aqueous solutions

[J]. Cellulose, 2015, 22: 3725

[本文引用: 1]

[18]

Kumari S, Chauhan G S, Ahn J H.

Novel cellulose nanowhiskers-based polyurethane foam for rapid and persistent removal of methylene blue from its aqueous solutions

[J]. Chem. Eng. J., 2016, 304: 728

[本文引用: 1]

[19]

Saucedo I, Guibal E, Roussy J, et al.

Uranium sorption by glutamate glucall: A modified chitosan part I: Equilibrium studies

[J]. Water SA, 1993, 19: 113

[本文引用: 1]

[20]

Leyva-Ramos R, Fuentes-Rubio L, Guerrero-Coronado R M, et al.

Adsorption of trivalent chromium from aqueous solutions onto activated carbon

[J]. J. Chem. Technol. Biotechnol., 1995, 62: 64

[本文引用: 1]

[21]

Haribabu E, Upadhya Y D, Upadhyay S N.

Removal of phenols from effluents by fly ash

[J]. Int. J. Environ. Stu., 1993, 43: 169

[22]

Han R P, Zhang J H, Zou W H, et al.

Biosorption of copper(II) and lead(II) from aqueous solution by chaff in a fixed-bed column

[J]. J. Hazard. Mater., 2006, 133: 262

DOIURLPMID [本文引用: 1] " />

The ability of Calabrian pine bark wastes (Pinus brutia Ten) for the removal of Fe(II) ions from aqueous solution at different concentrations and temperatures at a fixed pH was investigated. While the amounts of Fe(II) ions adsorbed onto the bark increased with increasing concentration, it increased slightly with increasing the temperature. Kinetics studies showed that adsorption process followed the first-order kinetic model as well as intra-particle diffusion kinetics. Adsorption isotherm followed both Langmuir and Freundlich models. And it was determined that the adsorption was favorable from a dimensionless factor, R(L). Furthermore, the thermodynamic parameters demonstrated that the removal of Fe(II) by the bark was a physical process.

[24]

Rengaraj S, Kim Y, Joo C K, et al.

Removal of copper from aqueous solution by aminated and protonated mesoporous aluminas: kinetics and equilibrium

[J]. J. Colloid Interface Sci., 2004, 273: 14

DOIURLPMID [本文引用: 1] class="outline_tb" " />

We report here initial results that demonstrate that cellulose can be dissolved without activation or pretreatment in, and regenerated from, 1-butyl-3-methylimidazolium chloride and other hydrophilic ionic liquids. This may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this important bioresource.

[11]

Lu Y, Sun Q F, Yu H P, et al.

Dissolution and regeneration of cellulose and development in processing cellulose-based materials with ionic liquids

[J].Chin. J. Org. Chem., 2010, 30: 1593

(盧蕓, 孫慶豐, 于海鵬等.

離子液體中的纖維素溶解、再生及材料制備研究進(jìn)展

[J]. 有機化學(xué), 2010, 30: 1593)

[12]

Qiu J, Wang Z Y, Sun Q, et al.

Effect of surface modification and hybridization of uhmwpe fibers on performance of their composites with epoxy resin

[J].Chin. J. Mater. Res., 2015, 29: 807

(邱軍, 王增義, 孫茜等.

表面改性和混雜對超高分子量聚乙烯纖維/環(huán)氧樹脂復(fù)合材料性能的影響

[J]. 材料研究學(xué)報, 2015, 29: 807)

[13]

Su X Y, Bai B, Ding C X, et al.

Preparation and water absorption/retention properties of coconut husk powders/ poly (acrylic acid-co-acryl amide) hybrid superabsorbent

[J].Mater. Rev., 2015, 29(6): 54

(蘇小育, 白波, 丁晨旭等.

椰糠粉/聚丙烯酸-丙烯酰胺復(fù)合吸水材料的制備及其吸保水性能

[J]. 材料導(dǎo)報, 2015, 29(6): 54)

[14]

Wang Y H, Wei X Y, Li J H, et al.

Homogeneous isolation of nanocellulose from cotton cellulose by high pressure homogenization

[J]. J. Mater. Sci. Chem. Eng., 2016, 1: 49

[15]

Zafeiropoulos N E, Vickers P E, Baillie C A, et al.

An experimental investigation of modified and unmodified flax fibres with XPS, ToF-SIMS and ATR-FTIR

[J]. J. Mater. Sci., 2003, 38: 3903

[16]

Samiey B, Tehrani A D.

Study of adsorption of Janus Green B and methylene blue on nanocrystalline cellulose

[J]. J. Chin. Chem. Soc., 2015, 62: 149

[17]

Mohammed N, Grishkewich N, Berry R M, et al.

Cellulose nanocrystal-alginate hydrogel beads as novel adsorbents for organic dyes in aqueous solutions

[J]. Cellulose, 2015, 22: 3725

[18]

Kumari S, Chauhan G S, Ahn J H.

Novel cellulose nanowhiskers-based polyurethane foam for rapid and persistent removal of methylene blue from its aqueous solutions

[J]. Chem. Eng. J., 2016, 304: 728

[19]

Saucedo I, Guibal E, Roussy J, et al.

Uranium sorption by glutamate glucall: A modified chitosan part I: Equilibrium studies

[J]. Water SA, 1993, 19: 113

[20]

Leyva-Ramos R, Fuentes-Rubio L, Guerrero-Coronado R M, et al.

Adsorption of trivalent chromium from aqueous solutions onto activated carbon

[J]. J. Chem. Technol. Biotechnol., 1995, 62: 64

[21]

Haribabu E, Upadhya Y D, Upadhyay S N.

Removal of phenols from effluents by fly ash

[J]. Int. J. Environ. Stu., 1993, 43: 169

[22]

Han R P, Zhang J H, Zou W H, et al.

Biosorption of copper(II) and lead(II) from aqueous solution by chaff in a fixed-bed column

[J]. J. Hazard. Mater., 2006, 133: 262

PMID " />

The ability of Calabrian pine bark wastes (Pinus brutia Ten) for the removal of Fe(II) ions from aqueous solution at different concentrations and temperatures at a fixed pH was investigated. While the amounts of Fe(II) ions adsorbed onto the bark increased with increasing concentration, it increased slightly with increasing the temperature. Kinetics studies showed that adsorption process followed the first-order kinetic model as well as intra-particle diffusion kinetics. Adsorption isotherm followed both Langmuir and Freundlich models. And it was determined that the adsorption was favorable from a dimensionless factor, R(L). Furthermore, the thermodynamic parameters demonstrated that the removal of Fe(II) by the bark was a physical process.

[24]

Rengaraj S, Kim Y, Joo C K, et al.

Removal of copper from aqueous solution by aminated and protonated mesoporous aluminas: kinetics and equilibrium

[J]. J. Colloid Interface Sci., 2004, 273: 14

PMID

A novel adsorbent, aminated and protonated mesoporous alumina, was prepared and employed for the removal of copper from aqueous solution at concentrations between 5 and 30 mg/l, in batch equilibrium experiments, in order to determine its adsorption properties. The removal of copper by the adsorbents increases with increasing adsorbent dosages. The adsorption mechanism is assumed to be an ion exchange between copper and the hydrogen ions present on the surface of the mesoporous alumina. The adsorbent was characterized by XRD, TEM, SEM, and BET methods. The sorption data have been analyzed and fitted to linearized adsorption isotherm of the Freundlich, Langmuir, and Redlich-Peterson models. The batch sorption kinetics have been tested for first-order, pseudo-first-order, and pseudo-second-order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results also showed that the intraparticle diffusion of Cu(II) on the mesoporous catalyst was the main rate-limiting step.

[25]

Chiron N, Guilet R, Deydier E.

Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic model

[J]. Water Res., 2003, 37: 3079

PMID

[26]

Hua K, Rocha I, Zhang P, et al.

Transition from bioinert to bioactive material by tailoring the biological cell response to carboxylated nanocellulose

[J]. Biomacromolecules, 2015, 17: 1224

PMID

[27]

Vadivelan V, Kumar K V.

Equilibrium, kinetics, mechanism, and process design for the sorption of methylene blue onto rice husk

[J]. J. ColloidInterface Sci., 2005, 286: 90

Heavy metal adsorbents prepared from the modification of cellulose: A review

1

2008