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近年来,随着工业的快速发展,土壤重金属污染问题日益加剧,目前常用的土壤修复技术主要包括物理修复、钝化修复、生物修复以及复合修复[1-3]。重金属钝化修复技术是指向污染土壤添加钝化材料,通过降低土壤中重金属有效含量或改变其赋存形态,阻止重金属迁移的土壤修复技术,通常用于修复中轻度污染土壤[4]。目前钝化材料多采用黏土矿物,如坡缕石、膨润土、海泡石、沸石等[5-9]。
坡缕石是一种富含镁铝型黏土矿物,在我国物量丰富、价格低廉且具极强吸附性,多用于重金属污染土壤修复[10-12]。但因矿物自身含大量杂质,为提高其使用效率,通常需对坡缕石原矿进行改性处理。改性坡缕石方法不一,主要分为物理方法和化学方法。常见的物理改性坡缕石方法主要有高温、超声波、微波改性等,而化学改性主要以酸碱改性与有机改性为主[13]。目前较多使用酸作改性处理,坡缕石经酸改性后内部结构及孔道杂质部分溶解,小孔数目及比表面积有所增加,吸附及离子交换性能提升[13-14],
陈雪芳等[15]研究发现坡缕石经酸改性后可去除自身部分杂质,有效比表面积提高。但目前为止,不同酸改性坡缕石吸附重金属能力存在差异,其优劣性尚未探明,需据使用目的,选择酸改性条件[16]。田振华等[13]研究表明,酸改性处理可溶解坡缕石内部的多面体结构,提高吸附性能,但过度酸改性会破坏坡缕石自身结构。
本文选用不同酸改性条件下的坡缕石对Ni-Cr污染土壤的钝化效果进行研究,以期根据污染土壤中重金属钝化及植物富集情况,筛选出修复Ni-Cr污染土壤的最佳钝化材料,为后续重金属污染土壤的治理及坡缕石应用提供理论依据和数据支撑。
酸改性坡缕石对Ni和Cr污染土壤的钝化效果
Stabilization of Ni and Cr in contaminated soil by acid-modified palygorskite
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摘要: 通过钝化实验与盆栽实验研究酸改性坡缕石对土壤中重金属Ni和Cr的钝化效果及植物富集的影响,结合可迁移性因子、钝化容量和修复效率对钝化效果进行评价。结果表明,10%和12.5%浓度硫酸处理72 h后的坡缕石对土壤中Ni和Cr的钝化效果显著高于原矿和其它酸改性处理,与对照相比,钝化容量分别提高了4.96倍与6.57倍。种植在这两种酸改性坡缕石钝化土壤中的植物内Ni和Cr的富集量显著低于其它钝化处理,富集量降低了79.77%与61.13%。随着酸改性坡缕石添加量的增加,重金属Ni与Cr由酸溶态转化为稳定性较强的可氧化态与残渣态,可迁移性因子整体降低,钝化容量和修复效率提高。酸改性坡缕石添加量为16 g·kg−1时,修复效率和钝化效果显著高于其它处理。 酸改性可显著提高坡缕石对土壤重金属的钝化修复效能,并且,酸改性坡缕石具有规模化应用在土壤重金属污染原位修复工程中的潜力。Abstract: The incubation and pot experiments were conducted to explore the influences of acid-modified palygorskite on stabilization efficiency and accumulation of Cr and Ni in contaminated soil, the stabilization efficiency was evaluated by mobolity fator (MF), stabilization capacity (Cap) and remediation ratio (RR). The results suggested that the stabilization efficiency of palygorskite modified by 10% and 12.5% H2SO4 72 h time of duration were significantly higher than raw mineral and other acid-modified palygorskite for Cr and Ni in soil, and the Cap was increased by 4.96 and 6.57 times, the accumulation content of Ni and Cr in corn planted in soils treated by these two acid-modified palygorskite reduced 79.77% and 61.13%, respectively. More acid-soluble Cr and Ni transformed into more inactive oxidizable and residual speciation with addition of acid-modified palygorskite, and MF decreased, Cap and RR increased. The Cap and RR were significantly higher than other treatments in 16 g·kg−1 additive amount of acid-modified palygorskite. The acid-modified treatment can evidently improve the stabilization function of palygorskite, and the acid-modified palygorskite has the potential for large scale in-situ remediation of soils polluted by heavy metals.
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Key words:
- palygorskite /
- Ni /
- Cr /
- stabilization /
- accumulation
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表 1 酸改性坡缕石钝化材料
Table 1. The stabilizer of palygorskite acid-modification
时间/h
TimeH2SO4质量分数 Mass fractions 2.5% 5% 7.5% 10% 12.5% 15% 12 S11 S21 S31 S41 S51 S61 24 S12 S22 S32 S42 S52 S62 36 S13 S23 S33 S43 S53 S63 48 S14 S24 S34 S44 S54 S64 72 S15 S25 S35 S45 S55 S65 96 S16 S26 S36 S46 S56 S66 表 2 不同酸改性坡缕石钝化剂对重金属Ni和Cr的钝化容量(mg·g−1)
Table 2. Stabilization capacity of different acid-modified palygorskite for heavy metals Ni and Cr (mg·g−1)
重金属
Heavy metalH2SO4质量分数/%
H2SO4 mass fractions酸处理时间 F 12 h 24 h 36 h 48 h 72 h 96 h Ni CK 1.21Cc 1.24Cb 1.26Da 1.24Eb 1.27Ca 1.26Da 1.87** 2.5 4.10Ac 3.97Bc 3.96Cc 4.34Db 4.61Ba 4.42Bb 1.99** 5 3.99Ab 3.57Bc 4.36Cb 4.64Da 4.75Ba 4.57Ca 6.86** 7.5 4.45Ab 3.74Bc 4.63Cb 4.81Ca 4.21Cb 3.92Bc 9.16** 10 3.92Bd 4.49Bc 4.73Cb 4.49Dc 6.16Aa 3.99Cd 2.57** 12.5 4.23Ad 4.61Bc 6.00Aa 5.89Aa 4.65Bc 5.64Ab 10.32** 15 4.84Ac 5.07Ab 5.61Ba 5.25Bb 5.82Aa 5.54Aa 2.64** F 46.08*** 25.14*** 52.32*** 77.41*** 32.93*** 75.42*** Cr CK 0.56Ea 0.54Eb 0.52Dc 0.51Ec 0.49Ec 0.50Dc 1.41** 2.5 0.79Cb 0.65Db 0.71Bb 1.13Ca 1.35Da 1.16Ca 12.94** 5 0.85Cc 0.67Dd 0.97Bb 1.11Ca 1.40Da 1.10Ca 56.22** 7.5 0.64De 0.92Cd 0.65Ce 1.24Bc 1.83Cc 3.09Aa 33.46** 10 2.96Aa 2.72Ac 2.97Aa 3.00Aa 2.85Bb 2.77Bc 29.57** 12.5 2.07Be 2.37Bd 2.57Ac 2.66Ab 3.22Aa 2.58Bc 2.13*** 15 2.52Ac 2.61Ac 2.85Ab 2.93Ab 2.86Bb 3.03Aa 1.45* F 101.68*** 38.45*** 73.66*** 53.14*** 28.17*** 30.92*** 注:大写字母表示不同酸改性H2SO4质量分数之间的差异性,小写字母表示不同酸改性时间之间的差异性;***表示极显著差异P<0.001,**表示较显著差异0.001<P<0.01,*表示显著差异0.01<P<0.05,以下同. Notes: Capital letters indicate the difference between different acid modified H2SO4 mass fractions, lowercase letters indicate the difference between different acid modification times. *** extremely significant difference P<0.001, ** more significant difference 0.001<P<0.01, * significant difference 0.01<P<0.05. The same below. 表 3 H2SO4质量分数和酸改性时间对玉米幼苗富集Ni和Cr含量影响的方差分析
Table 3. Variance analysis of the influence of H2SO4 fraction and pickling time on the accumulation content of Ni and Cr in corn
重金属
Heavy metal因素
Factor自由度
Degree of freedomF Ni 酸改性时间 6 40.594** H2SO4质量分数 6 24.776** 酸改性时间×H2SO4质量分数 36 4.984*** Cr 酸改性时间 6 18.649** H2SO4质量分数 6 12.677** 酸改性时间×H2SO4质量分数 36 3.135*** 表 4 不同酸改性坡缕石钝化处理下玉米幼苗富集Ni和Cr含量(mg·kg−1)
Table 4. The accumulation content of Ni and Cr in corn relative to different acid-modified palygorskite (mg·kg−1)
重金属
Heavy metalH2SO4质量分数/%
H2SO4 mass fractions12 h 24 h 36 h 48 h 72 h 96 h F Ni CK 261.27Aa 231.14Ab 229.31Ac 233.81Ab 229.22Ac 231.41Ab 3.22** 2.5 116.88 Ba 114.62Bb 113.51 Bb 110.87Be 102.61Bb 107.45Bd 65.21*** 5 111.36 Ba 107.22Bb 110.31 Ba 105.42 Bb 86.87Cc 99.26Cc 1403.37** 7.5 95.16 Ca 88.33 Cb 84.27 Cb 81.32 Cb 73.79 Dc 77.68 Dc 129.62** 10 83.21 Da 79.48 Db 76.81 Db 69.45 Dc 60.12Ed 64.78 Ec 217.40** 12.5 87.16 Da 81.43 Db 79.31 Dc 73.61 Dc 65.24Ec 67.33 Ed 329.91*** 15 98.43 Ea 93.26 Cb 72.55 Dc 70.43 Dc 68.47 Ed 71.40 Dc 11.91*** F 129.60*** 59.65*** 38.92*** 751.94*** 332.14*** 429.71*** Cr CK 246.18Aa 242.31Ab 239.18Ac 242.33Ab 239.72Ac 241.37Ab 7.63** 2.5 158.37 Bb 157.41 Ba 152.31 Bb 151.55 Bb 152.27 Ba 143.18 Bc 75.35** 5 148.34 Ca 145.22 Ca 141.61 Cb 147.25 Ca 137.74 Cc 139.16 Bb 602.94*** 7.5 136.45 Da 134.26 Da 126.64 Db 128.26 Db 115.87 Ec 124.13 Cb 356.26*** 10 129.60 Ea 126.42 Ea 122.27 Db 121.56 Db 102.41 Fd 111.16 Dc 79.60*** 12.5 125.25 Ea 121.22 Ea 114.32 Eb 108.34 Ec 93.17 Fd 106.42 Ec 276.35*** 15 141.22 Ca 120.31 Eb 120.11 Db 115.42 Ec 107.26 Ed 109.46 Ed 127.26*** F 192.02*** 132.91*** 236.04*** 245.36*** 601.85*** 886.70*** 表 5 酸改性坡缕石对土壤Ni和Cr迁移因子和修复效率的影响
Table 5. Effects of acid-modified palygorskite on migration factor and recovery on Ni and Cr
重金属
Heavy metal酸改性坡缕石
Acid-modified
palygorskite钝化指标
Stabilization indicator材料添加量 Material addition F 2 g·kg−1 4 g·kg−1 8 g·kg−1 16 g·kg−1 24 g·kg−1
Ni
S45MF 53.40±0.11a 52.91±0.06a 48.59±0.02c 44.95±0.03d 51.35±0.05b 6.85*** RRm 37.12±0.19d 39.46±0.14c 42.10±0.20b 44.26±0.11a 39.39±0.17c 21.08***
S55MF 56.17±0.04a 51.69±0.12b 53.04±0.14b 48.02±0.03c 49.78±0.07c 10.28*** RRm 37.12±0.12d 41.57±0.16b 39.29±0.21c 43.51±0.17a 43.08±0.15a 27.32***
Cr
S45MF 42.02±0.06a 39.95±0.04b 36.97±0.11c 31.03±0.03d 34.73±0.07c 7.95** RRm 49.18±0.13b 47.76±0.23c 49.97±0.18b 53.30±0.14a 52.27±0.22a 19.95**
S55MF 48.34±0.05a 42.95±0.13b 37.37±0.08c 33.28±0.06d 38.13±0.15c 11.17*** RRm 43.47±0.18d 45.27±0.09c 48.91±0.16b 51.27±0.11a 49.00±0.27b 41.12*** 注:同列不同小写字母表示各处理间存在差异性;***表示极显著差异P<0.001,**表示较显著差异0.001<P<0.01,*表示显著差异0.01<P<0.05. Notes: Significant differences among treatments are indicated by different lowercase letters. *** extremely significant difference P<0.001, ** more significant difference 0.001<P<0.01, * significant difference 0.01<P<0.05. -
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