聚胺壳聚糖微球对焦磷酸络合废水中镍的高效选择性去除特性与机制

Efficient removal of Ni(Ⅱ) from pyrophosphate-plating wastewater using the polyamine-grafted chitosan beads

针对含磷络合型电镀废水高效处理难题,本文探究了系列聚胺型壳聚糖微球(ACS_(x))对焦磷酸络合体系中镍离子的选择性去除特性.研究表明,焦磷酸的存在显著促进了ACS_(x)对镍的吸附.相同条件下,ACS_(1.0)—ACS_(1.75)对镍的吸附量超越前期报道的PAMD树脂3.2%—43.3%.过量的焦磷酸或其他常见共存物对ACS_(1.5)吸附镍的抑制率小于6%,其抗干扰能力远优于商品化树脂D001和D467.借助Visual MINTEQ形态计算和吸附等温线、动力学模型拟合以及XPS表征分析发现,络合体系中,NiP_(2)O_(7)^(2-)为主要的存在形态和吸附形态,其表观吸附动力学曲线高度符合拟二级动力学方程,初始吸附速率常数高于其他形态.推测NiP_(2)O_(7)^(2-)与ACS_(1.5)表面聚胺基团(含质子化胺基和中性胺基)发生了静电-配位耦合作用(-N~0-NiP_(2)O_(7)^(2-)·N_(-)^(+)),抗干扰性强.随着NiP_(2)O_(7)^(2-)的富集,焦磷酸配体空间位阻增大,导致部分焦磷酸根脱落,固相镍-焦磷酸吸附量比大于1.固定床动态吸附实验表明镍0.5 mmol·L^(-1)-焦磷酸1 mmol·^(-1)初始浓度下,流速4 BV·h^(-1),前18 BV出水镍浓度低于0.1 mg·L^(-1),镍饱和吸附容量为1.74 mmol·g^(-1).采用稀盐酸再生,镍脱附率为93.8%,浓缩倍率约为7.67倍.本研究表明ACS_(1.5)在实际处理焦磷酸镀镍清洗废水中具有较优的潜力.

To improve the advanced treatment of P-containing complexed plating wastewaters,the selective adsorption properties of Ni(Ⅱ) by series of polyamine-grafted chitosan beads(ACS_(x)) were investigated in various pyrophosphate(PP) complexed systems.The results showed that the presence of PP markedly promoted Ni(Ⅱ) adsorption by ACS_(x).Under the same condition,Ni(Ⅱ) adsorption by ACS_(1.0)—ACS_(1.75) was 3.2%—43.3% higher than those by the PAMD resin.The inhibition rate of excessive PP or other common coexistent on the adsorption of Ni(Ⅱ) by ACS_(1.5) was less than 6%,and its anti-interference ability was much better than that of commercial resins D001 and D467.According to the Visual MINTEQ speciation calculation,adsorption isotherm/kinetic models fitting and XPS characterization,NiP_(2)O_(7)^(2-) was the main species and adsorbate in the Ni-PP complexed systems.Its apparent adsorption kinetic curve was well fitted by pseudo-second-order kinetic equation.The fitted initial adsorption rate constant of NiP_(2)O_(7)^(2-) was higher than those of other species.It was speculated that NNiP_(2)O_(7)^(2-) has a coupling effect of coordination and electrostatic interaction(-N~0-NiP_(2)O_(7)^(2-)·N_(-)^(+)) with the polyamine groups containing both neutral amines and protonated amines,leading to the strong anti-interference ability.Along with the accumulation of NiP_(2)O_(7)^(2-) onto ACS_(1.5),part of PP decomplexed and released into the aqueous phase probably due to the steric hindrance,and the ratio of adsorption amount of Ni(Ⅱ) and PP was higher than 1.Furthermore,fixed-column adsorption tests showed that at C_(0,Ni)=0.5 mmol·L^(-1),C_(0,PP)=1.0 mmol·L^(-1) and 4 BV·h^(-1)of the flow rate,Ni(Ⅱ) concentration was lower than 0.1 mg·LNiP_(2)O_(7)^(2-) in the first 18 BV effluent and the saturated adsorption amount of Ni(Ⅱ) was 1.74 mmol·g^(-1).In addition,93.8% Ni(Ⅱ)could be recovered by diluted HCl,and the concentration ratio of Ni(Ⅱ) was about 7.67.The above trends suggest that the application of ACS_(1.5) in treating pyrophosphate-involved nickel-plating rinse wastewater is highly promising.