Effect of Chemical Agents on the Morphology and Chemical Structures of Microplastics

Abstract

Increased demand for plastics leads to a large amount of plastic manufacturing, which is accompanied by inappropriate disposal of plastics. The by-products of these waste plastics are microplastics (MPs; less than 5 nm in size), which are produced because of various environmental and physicochemical factors, posing hazardous effects to the ecosystem, such as the death of marine organisms due to the swallowing of plastic specks of no nutritional value. Therefore, the collection, preparation, identification, and recycling of these microsized plastics have become imperative. The pretreatment of MPs requires numerous chemical agents comprising strong acids, bases, and oxidizing agents. However, there is limited research on the chemical resistance of various MPs to these substances to date. In this study, the chemical resistance of five species of MPs (high-density polyethylene, low-density polyethylene, polystyrene, polyethylene terephthalate, and polypropylene) to sulfuric acid, hydrochloric acid, hydrogen peroxide, potassium hydroxide, and sodium hydroxide was studied. The MPs were reacted with these chemical reagents at preset temperatures and durations, and variations in morphology and chemical structures were detected when the MPs were reacted with mineral acids, such as sulfuric acid. The data pertaining to these changes in MP properties could be a significant reference for future studies on MP pretreatment with strong acids, bases, and oxidizing agents.

Microplastics determination and quantification in two benthic filter feeders Sabella spallanzanii, Polychaeta and Paraleucilla magna, Porifera

“…Some authors have summarized the different chemical digestion approaches (acid; alkaline; oxidizing) focusing on the plastic recovery after treatment, in order to assess the riskiest or safest procedures [ [58] , [59] , [60] , [61] ]. In many cases acids (in particular HNO 3 ) have been considered dangerous to use in MPs extraction procedure: they can damage plastics causing melting and discoloration or alter their FTIR and Raman spectra causing problems during spectroscopy identification [ [60] , [61] , [62] ].…”

“…It has been recently reported that reducing concentration of HNO 3 improves the plastic stability even for prolongated exposure time (18 h) at high temperature 80 °C [ 58 ]. On the other hand, recently, has been assessed the effect of different not diluted reagents (HCl, KOH, NaOH, H 2 O 2 , H 2 SO 4 ) and digestion conditions (1 or 7 days at 25 °C or 70 °C) on MPs [ 59 ]. From these experiments HDPE, LDPE, PP and PET MPs resulted stable from morphological and spectroscopical point of view in presence of HCl, H 2 O 2 , KOH, and NaOH at all reaction conditions, while PS showed some abrasion when exposed to bases at 70 °C for 24 h or 7 days [ 59 ].…”

Environmental stress cracking of chemically aged HDPE-100 gas pipe under impact fracture mode

“…In the case of acids, several studies have shown the generally adverse effects on both structure and on physical properties of HDPE and polypropylene (PP) as shown in Table 1a for the case of transportation pipes [20][21][22][23][24] and in Table 1b for others specific applications [25][26][27][28].…”

“…Table 1a. Literature survey of HDPE pipe interactions with sulfuric and hydrochloric acids Indeed, damage degrees, following exposure to H2SO4 or HCl acids over variable ageing periods, are complex and multifaceted [27,29]. Significant alterations of HDPE structure together with preeminent increases and/or decreases in mechanical and thermal properties are observed.…”

“…Significant alterations of HDPE structure together with preeminent increases and/or decreases in mechanical and thermal properties are observed. When mechanical loads, thermal effects and exposition to chemically aggressive conditions are combined, resulting polymer degradations and service lifetime reduction may become even more significant [20,[25][26][27][28]. HDPE pipe networks for transmission and distribution of fluids fall in the category of fluidpolymer interactions.…”