CN110302762A - 基于褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法、应用 - Google Patents
基于褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法、应用 Download PDFInfo
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Abstract
本发明公开一种褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法、应用。以褐煤提质后的小颗粒(废弃物)为原材料,通过水蒸汽活化法制备褐煤基活性炭(LAC),然后在其表面通过聚丙烯酸(PAA)原位聚合引入酸性表面基团而得到低成本吸附剂LAC/PAA,其中原位聚合包括硝酸预处理、PAA原位接枝、烘干和固化步骤。该吸附剂应用于水处理或空气净化。本发明产品含有活性炭本身的微孔及中孔结构,使其兼具吸附功能;与普通净水厂用活性炭相比(pH=6~10),由于其表面酸性基团增加(pH=4.8),从而获得了吸附去除重金属的功能。该产品以废弃物为原料,生产成本低,环境友好性、经济效益好且节约资源,对推动社会可持续发展具有积极的意义。
Description
技术领域
本发明涉及活性炭制备及改性技术领域,特别涉及一种褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法、应用。
背景技术
用于从稀释的水溶液中除去重金属的常用方法包括化学沉淀、过滤、吸附(活性炭,多 壁碳纳米管,飞灰,沸石,高岭石和树脂等)、氧化、还原、离子交换、电解法,膜分离法和 基因工程法等[8]。其中,化学沉淀是一种简单有效的方法,适用于处理大量水,并被广泛使 用[19];此外,吸附因操作过程灵活、经济效率较高,是另一种最有效的去除重金属的方法[8,20],尤其是含酸性表面官能的团活性炭,它可以在非常低的浓度吸附金属[11,21]。至于其他方 法,由于处理成本高,实际应用中有许多问题需要解决,限制了它们的应用和发展[22,23]。
考虑到饮用水应急污染处理的特点(大量水、浓度低),以褐煤提质副产物(一种废物) 为原材料开发了一种低成本去除低浓度重金属的吸附剂LAC/PAA。
参考文献:
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发明内容
本发明的目的在于克服上述现有技术的不足,提出制备一种褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法,解决饮用水中低浓度Pb(II)的污染问题,有效保障饮用水安全。
本发明以褐煤提质副产物(一种废物)作为制备褐煤基活性炭(Ligniteactivated carbon, LAC)的原料,充分体现了低成本的原则。因为金属离子在于溶液中通常作为离子或含水离子络合物存,因此,没有任何表面预处理的活性炭(AC)对金属离子的吸附能力从一般到低到零[21]。因此,需要进行LAC的预处理以增强其酸性表面官能团,从而促进金属离子的吸收。本发明中,通过在LAC表面上的原位聚合引入就丙烯酸(PAA),该材料也可以通过廉价材料-丙烯酸[24]的聚合容易地获得。
本发明的第一个技术方案是:褐煤提质副产物的去除低浓度重金属的低成本吸收剂及其制备方法,以褐煤提质副产物(废弃物)为原材料,通过气体活化法制备LAC,在此基础上,通过原位接枝聚丙烯酸(PAA)而得到吸附剂LAC/PAA,包括如下步骤:
具体包括如下步骤:
1)以褐煤提质后的小颗粒为原料,采用水蒸气活化法进行活化
(1)水蒸气用量:2~16kg水蒸气/kg LAC;
(2)活化升温速率:小于5~15℃/min;
(3)活化反应:活化温度在500-850℃,活化时间为1-3.5h,制备出LAC;
2)LAC/PAA是通过HNO3预处理,PAA接枝,干燥和固化
(1)预处理LAC:
首先,用10%~20%HNO3(v/v)溶液预处理LAC 30~60分钟;
然后用去离子水反复洗涤直至溶液pH不变;
将预处理的LAC在105℃下干燥3小时以除去水分,之后将其置于干燥器中冷却后备用;
(2)在室温下将预处理后的LAC与1%~5%PAA混合来进行PAA的原位接枝得到混合物;
(3)将混合物在105℃下干燥3小时以除去水分,然后在170~200℃下固化1小时,得到LAC /PAA,置于干燥器中冷却后使用。
本发明表面酸性基团通过聚丙烯酸(PAA)原位聚合引入。
本发明所述步骤1)活化过程要保证活化炉内处于正压状态。
本发明所述步骤1)中活化反应采用的活化剂选选自二氧化碳、氧气和空气中的至少一种。
本发明所述步骤2)-(1)中处理过程中要不断进行搅拌以使其反应均匀。
本发明所述步骤2)-(2)中PAA的含固量为30%。
本发明的第二个技术方案是褐煤提质副产物的去除低浓度重金属的低成本吸收剂,采用上述制备方法,含有微孔、中孔,和表面酸性基团,使其兼具吸附有机物和去除重金属功能。
本发明孔径分布由褐煤基活性炭的制备过程调控。
本发明的第三个技术方案是褐煤提质副产物的去除低浓度重金属的低成本吸收剂的应用,其特征在于,应用于水处理或空气净化。
本发明相对于现有技术有以下有益效果:
1、本发明以褐煤升级副产物(一种废弃物)为原料制备活性炭(LAC),变废为宝、节约资源,而原位聚合所用的PAA亦可以通过廉价材料-丙烯酸的聚合很容易的得到,充分体现了低成本、可持续发展的原则。
2、本发明制备出的LAC/PAA不仅含有普通活性炭所具有的微孔、中孔结构,从而使LAC/ PAA兼具吸附有机污染物的功能;而且包含表面酸性官能团,从而获得了去除重金属的功能。
3、该低成本吸附剂的污染物去除效率高,更重要的是便于与传统的水处理工艺相结合,因此,运用LAC/PAA进行水处理得以充分考虑水处理的实际因素、进而达到解决应急污染问题以及节约资源的目的。
4、本发明成本低,环境友好性、经济效益好且节约资源,对推动社会可持续发展具有积极的意义。
附图说明
图1是LAC/PAA的制备及应用流程图。
图2是LAC/PAA对Pb(II)的吸附能力和吸附等温线模型拟合:
(a)LAC/PAA对Pb(II)的吸附能力;(b)Freundlich和Langmiur吸附等温线模型拟合。
图3是LAC/PAA对Pb(II)的吸附动力学试验和模型拟合:
(a)动力学试验;(b)伪二级动力学模型拟合。
图4是LAC/PAA对Hg(II)的吸附等温线及模型拟合:
(a)Langmiur吸附等温线;(b)Freundlich吸附等温线。
图5是LAC/PAA对Hg(II)的吸附能力和动力学拟合:
(a)LAC/PAA对Hg(II)的吸附能力;(b)伪二级动力学模型拟合。
图6是LAC/PAA吸附Pb(II)前后的FT-IR图谱:
(a)吸附Pb(II)之前;(b)吸附Pb(II)之后。
具体实施方式
下面通过具体实施例和附图对本发明作进一步的说明。本发明的实施例是为了更好地使本领域的技术人员更好地理解本发明,并不对本发明作任何的限制。
本发明的制备方法采用如下实施例进行,但不限于:
实施例1:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(8kg水蒸气/kgLAC) 制备出LAC(活化升温速度:5℃/min,活化温度:500℃,活化时间:3.5h);然后,用20%HNO3(v/v)溶液对LAC预处理30分钟,之后再用去离子水反复洗涤直至溶液pH不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与3%的PAA (wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在180℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
实施例2:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(8kg水蒸气/kgLAC) 制备出LAC(活化升温速度:10℃/min,活化温度:850℃,活化时间:1.5h);然后,用15% HNO3(v/v)溶液对LAC预处理45分钟,之后再用去离子水反复洗涤直至溶液pH不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与1%的PAA(wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在190℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
实施例3:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(16kg水蒸气/kg LAC)制备出LAC(活化升温速度:15℃/min,活化温度:700℃,活化时间:1.0h);然后,用10%HNO3(v/v)溶液对LAC预处理60分钟,之后再用去离子水反复洗涤直至溶液pH 不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与5%的 PAA(wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在200℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
实施例4:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(2kg水蒸气/kgLAC)制备出LAC(活化升温速度:12℃/min,活化温度:600℃,活化时间:2.0h);然后,用18%HNO3(v/v)溶液对LAC预处理35分钟,之后再用去离子水反复洗涤直至溶液pH 不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与4%的 PAA(wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在170℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
实施例5:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(6kg水蒸气/kgLAC)制备出LAC(活化升温速度:8℃/min,活化温度:650℃,活化时间:2.5h);然后,用15%HNO3(v/v)溶液对LAC预处理45分钟,之后再用去离子水反复洗涤直至溶液pH 不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与3.5%的PAA(wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在 200℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
实施例6:首先,以褐煤提质后的小颗粒为原料,采用水蒸气活化法(14kg水蒸气/kg LAC)制备出LAC(活化升温速度:12℃/min,活化温度:600℃,活化时间:1.8h);然后,用15%HNO3(v/v)溶液对LAC预处理45分钟,之后再用去离子水反复洗涤直至溶液pH 不变,并置于干燥器内在105℃下干燥3小时以除去水分;最后,将预处理后的LAC与2%的 PAA(wt.30%)混合原位接枝,混合均匀后,在105℃下干燥3小时去除水分,然后再在180℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
上述实施例1制得的LAC/PAA的物理特性、孔隙结构参数及吸附性能分析结果如下:
1.1物理特性及孔隙结构参数
实施例1所制备的LAC与LAC/PAA的物理特性和孔隙结构参数如表1-1所示。
表1-1实施例1所制备的LAC与LAC/PAA的物理特性和孔隙结构参数
注:1.SBET,BET比表面积;2.Smic,t法微孔表面积;3.Vmic,微孔容积;4.Vmeso,BJH 法累计脱附孔容积;5.Dav,平均孔径。
从表1-1可以看出,与LAC相比,LAC/PAA的BET比表面积下降20.3%,微孔表面积下降21.3%,微孔体积下降11.4%,但Vmeso和Dav增加。即,硝酸预处理破坏了LAC中的部分微孔和大孔,导致了BET比表面积的减少和Vmeso和Dav的增加。此外,灰分降低了6%,这应该归因于硝酸对无机离子的氧化去除。其中,最重要的变化是pH值从LAC的8.71下降到LAC/PAA的4.83,这表明LAC的酸性表面官能团增加了,即有利于金属离子的去除。 LAC/PAA的其他物理性质,如表观密度和灰分,没有显着变化,即,在引入酸性基团后,对LAC的影响较小。
1.2吸附性能研究
1.2.1吸附等温线分析
由于LAC/PAA是为饮用水处理痕量Pb(II)污染而开发的,因此吸附试验在低浓度(约 50μg/L)下进行,该值是WHO水质准则标准限值的10倍。
LAC/PAA对Pb(II)的吸附能力如图2a所示,表明随着LAC/PAA用量的增加,Pb (II)的浓度从56.14μg/L降至10μg/L以下,即,LAC/PAA可有效去除Pb(II),出水可达到WHO水质准则的要求。与LAC(31%)相比,LAC/PAA对Pb(II)的去除率提高了2.9倍,即在LAC表面引入的酸性表面官能团有效地提高了其吸附金属离子的能力。
基于吸附实验结果,分别采用两种广泛使用的等温模型(Freundlich和Langmiur吸附等温线)拟合实验数据,结果如图2b所示。结果表明,LAC/PAA对Pb(II)的吸附特性更符合Freundlich吸附等温线,其R2值为0.961,高于Langmiur吸附等温线(R2=0.9057)。
1.2.2吸附动力学分析
LAC/PAA对Pb(II)的吸附动力学实验也在初始Pb(II)浓度约为50μg/L时进行,其结果如图3a所示,其中,LAC/PAA剂量保持在60mg/L,根据图2a可知,该剂量是足够的。
从图3a中可以看出,溶液中Pb(II)浓度在吸附过程的最初几分钟内迅速下降,几乎在 20分钟内,出水Pb(II)浓度达到了WTO水质准则的要求,即LAC/PAA对Pb(II)的吸附充分体现了化学反应的特征。为了进一步确定吸附过程的机理,采用三种动力学模型(伪一阶模型,伪二阶模型和粒子内扩散)模式)对该吸附过程进行了拟合。结果表明,拟二级动力学模型的R2值为0.961,大于本研究中测试的其他动力学模型的R2值。因此,Pb(II)在LAC /PAA上的吸附是由于重金属与LAC/PAA之间共享或交换电子的化学过程所引起的,验证了金属阳离子表面酸性基团对Pb(II)的螯合属性。
LAC/PAA对Hg(II)的吸附显示出与去除Pb(II)相似的性质。其结果分别如图4、5所示。
1.2.3LAC/PAA吸附Pb(II)前后的FT-IR光谱分析
为了研究LAC/PAA对重金属的吸附机理,对LAC/PAA吸附Pb(II)前后的样品进行了FT-IR光谱分析,其结果如图6所示。
由图6可知,在吸附Pb(II)后,观察到LAC/PAA表面中有明显的1665-1565cm-1吸收峰(图6b),这应该归因于羧酸盐的不对称伸缩振动,并证实了羧基的存在。对于1385cm-1处的另一个特征峰则应归因于由Pb(NO3)2引入的NO3 -的吸附峰。FT-IR光谱中3400cm-1处的吸附峰是由于样品表面吸附的水,而1100-1030cm-1之间的另一个宽带应属于-C-O-H拉伸和 -OH变形价值观;此外,由于表面极性基团的含量相对较少,在两个光谱之间没有观察到显着差异。
Claims (9)
1.褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,以褐煤提质副产物为原材料,通过气体活化法制备LAC,在此基础上,通过原位接枝聚丙烯酸而得到吸附剂LAC/PAA;
具体包括如下步骤:
1)以褐煤提质后的小颗粒为原料,采用水蒸气活化法进行活化
(1)水蒸气用量:2~16kg水蒸气/kg LAC;
(2)活化升温速率:小于5~15℃/min;
(3)活化反应:活化温度在500-850℃,活化时间为1-3.5h,制备出LAC;
2)LAC/PAA是通过HNO3预处理,PAA接枝,干燥和固化
(1)预处理LAC:
首先,用10%~20%HNO3(v/v)溶液预处理LAC30~60分钟;
然后用去离子水反复洗涤直至溶液pH不变;
将预处理的LAC在105℃下干燥3小时以除去水分,之后将其置于干燥器中冷却后备用;
(2)在室温下将预处理后的LAC与1%~5%PAA混合来进行PAA的原位接枝得到混合物;
(3)将混合物在105℃下干燥3小时以除去水分,然后在170~200℃下固化1小时,得到LAC/PAA,置于干燥器中冷却后使用。
2.根据权利要求1所述的褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,表面酸性基团通过聚丙烯酸原位聚合引入。
3.根据权利要求1所述的褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,所述步骤1)活化过程要保证活化炉内处于正压状态。
4.根据权利要求1所述的褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,所述步骤1)中活化反应采用的活化剂选选自二氧化碳、氧气和空气中的至少一种。
5.根据权利要求1所述的褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,所述步骤2)-(1)中处理过程中要不断进行搅拌以使其反应均匀。
6.根据权利要求1所述的褐煤提质副产物的去除低浓度重金属的低成本吸收剂的制备方法,其特征在于,所述步骤2)-(2)中PAA的含固量为30%。
7.根据权利要求1至6中任一项所述的制备方法制备吸收剂,其特征在于,含有微孔、中孔,和表面酸性基团。
8.根据权利要求7所述的吸收剂,其特征在于,孔径分布由褐煤基活性炭的制备过程调控。
9.褐煤提质副产物的去除低浓度重金属的低成本吸收剂的应用,其特征在于,应用于水处理或空气净化。
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