聚氯乙烯（PVC）废塑料及氯化石蜡（Chlorinated paraffins, CPs）废物等高氯含量有机废物因其潜在毒性且难以自然降解而受到广泛关注。因含大量氯元素和塑化剂，目前这两种废物无法用焚烧、填埋等传统方法处理，焚烧易产生氯代二噁英等高毒性物质，而填埋会导致氯化物、塑化剂等有毒物质对土壤和地下水的污染。安全高效脱氯是PVC和CPs两类废物无害化、资源化的关键环节。本文以富含邻苯二甲酸二异辛酯（DEHP）塑化剂的PVC废物及含氯量52 %的氯化石蜡（52# CPs）为对象，研究了亚临界水-氨体系中PVC废物的脱氯行为及塑化剂DEHP的分解机制，比较研究了PVC废物在亚临界水、亚临界甲醇、亚临界水-氨三个体系中的脱氯特性及残渣碳材料对六价铬离子的吸附行为，研究了亚临界水-碱体系中不同碱性物质对52# CPs脱氯行为的影响和脱氯路径。主要结果如下：

（1）亚临界水-氨体系中PVC废物的脱氯行为及塑化剂DEHP的分解机制。亚临界水-氨温度升高、停留时间增加均有利于提高脱氯率。250 ℃、60 min、5 %氨浓度，PVC脱氯效率达94.8 %。脱氯路径为直接脱氯化氢，固相产物为多烯结构。不同温度条件下可回收得到不同的油相产物。250 ℃条件下，亚临界水-氨条件可显著促进DEHP的水解并导致油相产物含86.12 %的塑化剂合成单体2-乙基-1-己醇，回收附加值高。温度升高到400 ℃，油相产物中2-乙基-1-己醇浓度降至10.16 %，苯甲醛和苯乙酮的浓度分别增加到20.48 %和26.63 %。苯甲醛和苯乙酮来源于PVC脱氯产物多烯结构的进一步环化、分解、部分氧化等过程。因此，亚临界水-氨介质中两阶段温度式的PVC废物处理可实现2-乙基-1-己醇、苯甲醛和苯乙酮等高附加值化学品的高效回收。

（2）PVC废物在亚临界水、亚临界甲醇、亚临界水-氨三个体系中的脱氯特性及脱氯后残渣碳材料对六价铬离子的吸附行为的比较研究。分别将上述三个体系不同反应条件下获得的固体残渣用于Cr（VI）离子的吸附研究，优选出获得具有最佳吸附性能残渣的PVC脱氯反应条件为：亚临界水体系（R₁：300 ℃，60 min，1：30 g/mL），脱氯率接近100 %；亚临界甲醇体系（R₂：200 ℃，30 min，1：30 g/mL），脱氯率44.9 %；亚临界氨水体系（R₃：250 ℃，60 min，1：30 g/mL），脱氯率接近100 %。PVC在亚临界水、亚临界甲醇、亚临界水-氨三个体系脱氯获得R₁（亚临界水）、R₂（亚临界甲醇）和R₃（亚临界水-氨）三种残渣。Cr（VI）离子吸附实验表明R₁、R₃在pH为2的条件下吸附效果最优，吸附量分别为9.41 mg/g、7.59 mg/g。R₂在pH为10的条件下吸附量最大为7.17 mg/g。R₁、R₃主要以单层吸附为主，R₂主要以多层吸附为主。R₁、R₂吸附过程ΔH＜0为自发性吸附，R₃吸附过程ΔH＞0。PVC废物在亚临界水、甲醇、氨水体系脱氯处理后的固体残渣可作为吸附材料用于六价铬离子的吸附去除。

（3）亚临界水和亚临界水-碱体系对52# CPs脱氯行为的影响和脱氯路径。亚临界水反应300 ℃、45 min条件下可实现52# CPs完全脱氯。在亚临界水-氢氧化钠体系，在反应250 ℃、5 min、2 mL（0.05mol/l） NaOH条件下实现52# CPs完全脱氯。KOH、Na₂CO₃、NaHCO₃、NH₃·H₂O等碱性添加剂可有效强化亚临界水对52# CPs的脱氯并降低处理温度、缩短处理时间。在250 ℃、5 min、1：5 mL/mL（52# CPs/（2 mL碱性添加剂＋H₂O）mL/mL）反应条件，发现碱性添加剂对52# CPs的脱氯都接近完全。在250 ℃、5 min、1：15（52# CPs/（2 mL碱性添加剂＋H₂O）mL/mL）反应条件，发现NaOH脱氯效果最好为97 %，其次为Na₂CO₃其脱氯率为65.4 %，最后依次为NaHCO₃、NH₃·H₂O、KOH，证明了Na₂CO₃作为强碱替代品，具有一定应用前景。52# CPs亚临界水脱氯主要以羟基取代路径为主，产物主要为1，2，6-己三醇等多元醇化合物。引入NaOH强化剂后52# CPs主要脱氯化氢为主要反应路径，产物主要为2，4-己二炔等不饱和烃。从52# CPs脱除的氯全部以无机氯的形式转移至水相而回收。

Organic wastes with high chlorine content, such as polyvinyl chloride (PVC) waste plastics and chlorinated paraffins (CPs) waste, have received widespread attention because of their potential toxicity and difficulty in natural degradation. Because of the large amount of chlorine and plasticizers, these two wastes cannot be treated by traditional methods such as incineration and landfills, which are prone to produce highly toxic substances such as chlorinated dioxins, while landfills can lead to soil and groundwater contamination by chlorinated substances, plasticizers and other toxic substances.Safe and efficient dechlorination is a key link in the environmentally sound and resourceful treatment of both PVC and CPs wastes. In this paper, we studied the dechlorination behavior of PVC waste and the decomposition mechanism of plasticizer DEHP in subcritical water-ammonia system by using PVC waste rich in diisooctyl phthalate (DEHP) plasticizer and chlorinated paraffin (52#   CPs) with 52 % chlorine content, and comparatively studied the dechlorination characteristics of PVC waste in three systems of subcritical water, subcritical methanol and subcritical water-ammonia and the residue The adsorption behavior of carbon materials on hexavalent chromium ions was studied, and the effects of different alkalis in the subcritical water-alkali system on the dechlorination behavior of 52# CPs and the dechlorination pathway were investigated. The main results are as follows.

(1) Dechlorination behavior of PVC waste in subcritical water-ammonia system and the decomposition mechanism of plasticizer DEHP. The increase of subcritical water-ammonia temperature and residence time were both beneficial to improve the dechlorination rate. 250 ℃, 60 min, 5 % ammonia concentration, PVC dechlorination efficiency reached 94.8 %. The dechlorination path was direct dechlorination of HCl, and the solid phase product was polyene structure. At 250 ℃, the subcritical water-ammonia condition significantly promoted the hydrolysis of DEHP and led to the oil phase product containing 86.12 % of the plasticizer synthesis monomer 2-ethyl-1-hexanol with high recovery added value. When the temperature was increased to 400 °C, the concentration of 2-ethyl-1-hexanol in the oil phase product decreased to 10.16 %, and the concentration of benzaldehyde and acetophenone increased to 20.48 % and 26.63 %, respectively. Benzaldehyde and acetophenone originated from the further cyclization, decomposition, and partial oxidation of the polyene structure of PVC dechlorination products. Therefore, two-stage temperature-based PVC waste treatment in subcritical water-ammonia media can achieve efficient recovery of high-value-added chemicals such as 2-ethyl-1-hexanol, benzaldehyde, and acetophenone.

(2) A comparative study of the dechlorination characteristics of PVC waste in three systems: subcritical water.subcritical methanol and subcritical water-ammonia and the adsorption behavior of residual carbon material on Cr(VI) ions after dechlorination. The solid residues obtained under different reaction conditions of the above three systems were used for the adsorption of Cr(VI) ions, respectively, and the PVC dechlorination reaction conditions with the best adsorption performance residues were preferably selected as follows:Subcritical water system (R₁: 300 ℃, 60 min, 1:30 g/mL), dechlorination rate close to 100 %; subcritical methanol system (R₂: 200 ℃, 30 min, 1:30 g/mL), dechlorination rate of 44.9 %; subcritical ammonia system (R₃: 250 ℃, 60 min, 1:30 g/mL), dechlorination rate close to 100 % .PVC was dechlorinated in subcritical water, subcritical methanol and subcritical water-ammonia systems to obtain three residues, R₁ (subcritical water), R₂ (subcritical methanol) and R₃ (subcritical water-ammonia).Cr(VI) adsorption experiments showed that R₁ and R₃ had the best adsorption effect at pH 2, with adsorption amounts of 9.41 mg/g and 7.59 mg/g, respectively. R₂ adsorbed at a maximum of 7.17 mg/g at pH 10. R₁ and R₃ mainly adsorbed in monolayer, and R₂ mainly adsorbed in multilayer. ΔH < 0 for R₁ and R₂ adsorption processes, and ΔH > 0 for R₃ adsorption process. The solid residue of PVC waste after dechlorination in low temperature subcritical water, methanol and ammonia system can be used as adsorbent material for the adsorption removal of hexavalent chromium ions.

(3) Effects of subcritical water and subcritical water-alkali system on the dechlorination behavior and dechlorination path of 52# CPs. Complete dechlorination of 52# CPs could be achieved under the condition of 300 ℃ and 45 min of subcritical water reaction. In the subcritical water-sodium hydroxide system, complete dechlorination of 52#CPs was achieved at 250 ℃, 5 min and 2 mL (0.05 mol/l) NaOH. alkaline additives such as KOH, Na₂CO₃, NaHCO₃ and NH₃·H₂O could effectively enhance the dechlorination of 52# CPs by subcritical water and reduce the treatment temperature and treatment time. Under the reaction conditions of 250 ℃, 5 min, and 1:5 mL/mL (52# CPs/(2 mL alkaline additives + H₂O) mL/mL), the dechlorination of 52# CPs by alkaline additives was found to be nearly complete. At 250 ℃, 5 min, 1:15 (52# CPs/(2 mL alkaline additive + H₂O) mL/mL) reaction conditions, the best dechlorination effect of NaOH was found to be 97 %，followed by Na₂CO₃ with 65.4 % dechlorination, and finally NaHCO₃,NH₃·H₂O, and KOH in order, which proved that Na₂CO₃ as a strong alkali alternative has certain application prospects. The subcritical water dechlorination of 52# CPs was mainly based on the hydroxyl substitution path, and the products were mainly polyol compounds such as 1,2,6-hexanetriol. After the introduction of NaOH enhancer, the main reaction path of 52# CPs is dechlorination of hydrogen chloride, and the products are mainly unsaturated hydrocarbons such as 2,4-hexadiyne. All the chlorine removed from 52# CPs was recovered in the form of inorganic chlorine transferred to the aqueous phase.

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