Energy Recovery from Acid-Base Neutralization Through pH-Sensitive Polymers: Novel Application of Donnan Osmosis

利哈伊大学最近的研究已经证明了从涉及氢和氢氧根离子缔合的酸碱中和反应产生有用能量的可能性。许多工业过程和天然地球化学过程（例如，酸性矿井排水）产生酸性（或碱性）废水流，并且在处置之前需要中和。酸碱反应在热力学上非常有利，产生大量热能。由于进行处理的废酸溶液通常非常稀，中和反应中产生的大量热能导致主体水相温度的微小增加。因此，任何能量回收几乎是不可能的，迄今为止还没有报道。对于该项目，建议通过在含有共价连接的弱酸或弱碱官能团的适当pH敏感的亲水性聚合物（或生物聚合物）内进行中和反应，可以回收大量的有用能量。从科学上讲，唐南渗透现象驱动了导致能量产生的过程，并且不需要外部膜。当与酸或碱接触时，pH的变化导致官能团可逆地获得和失去其离子特性。这种变化引起了在聚合物相内部产生渗透压的开关模式，导致其由于水进出聚合物相的运动而可逆地溶胀（渗透）和收缩（反渗透）。因此，酸碱中和伴随着产生可用的机械能。值得注意的是，该过程完全是碳中和的，不会产生温室气体。所提出的工艺具有使用可重复使用的pH敏感性聚合物从废酸和废碱流在全球产生能量的潜力。全球硫酸年产量估计约为2亿吨。假设1%的这种酸出现在被所提出的能量回收过程中和的废物流中，与用化石燃料产生相同量的能量的工厂相比，二氧化碳排放量的减少将超过6000万吨。

(Sengupta)1065651 Recent studies at Lehigh University have demonstrated the possibility of generating useful energy from acid-base neutralization reactions involving association of hydrogen and hydroxyl ions. Many industrial processes and natural biogeochemical process (e.g., acid mine drainage) produce acidic (or basic) wastewater streams and require neutralization prior to disposal. The acid-base reaction is thermodynamically very favorable with generation of significant amount of thermal energy. Since the waste acid solution undergoing treatment is often very dilute, the significant amount of thermalenergy generated in the neutralization reaction causes a miniscule increase in the temperature of the bulk aqueous phase. As a result, any energy recovery is nearly impossible and has not been reported to date. For this project, it is proposed that it is possible to recover significant amount of useful energy by carrying out the neutralization reaction inside an appropriate pH-sensitive hydrophilic polymer (or biopolymer) containing covalently attached weak-acid or weak-base functional groups. Scientifically, the phenomenon of Donnan osmosis drives the process leading to energy generation and no external membrane is necessary. When contacted with acid or base, the variation in pH causes the functional groups to reversibly acquire and lose its ionic character. This change gives rise to on-off pattern of generation of osmotic pressure inside the polymer phase causing it to reversibly swell (osmosis) andshrink (deosmosis) due to the movement of water in and out of the polymer phase. Thus, acid-base neutralization is accompanied by generation of usable mechanical energy. It is noteworthy that the process is completely carbon neutral and no greenhouse gas is produced. The proposed process has the potential to generate energy globally from waste acid and waste alkali streams using reusable pH-sensitive polymers. The global annual production of sulfuric acid is estimated to be approximately 200 million tons. Assuming 1% of this acid appears in the waste stream that is neutralized by the proposed energy recovery process, reduction in carbon dioxide emission in comparison with a plant producing the same amount of energy with fossil fuel will be over 60 million tons.