Latest developments in membrane materials and boron removal technology

Latest developments in membrane materials and boron removal technology

1.Introduction

Boron is not only a micronutrient essential for humans, but also an important raw material for many industries such as agriculture, agriculture and agriculture. Production of glass fiber, detergent, fertilizer, etc. [1]. However, boron has recently been restored to inevitable contaminants in various water supplies for various reasons. First, due to strong demand in the agricultural, ceramic and glass markets, boron production and consumption have shown steady growth in recent years [2]. Leakage of boron compounds into various water bodies can cause serious environmental problems. Second, many researchers have gradually revealed the toxicity of boron to plants, animals and humans [2-4]. As a result, boron concentrations in drinking water have been regulated in most countries and regions, such as the EU recommended 1.0 mg L-1 [5] and the WHO 2.4 mg L-1 [6]. In some industries, such as semiconductor manufacturing, the control of boron in ultrapure water is more stringent [1,12]. Therefore, it is important to remove boron from water to produce qualified water for a variety of applications.

 

The membrane technology for removing boron has been concerned for decades [7]. Today, membrane-based separation processes have become important alternatives to traditional technologies in many applications due to their environmental friendliness and energy/cost efficiencies [8]. According to the nature of the membrane and its mass transfer mechanism, these membrane separation processes can be divided into microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, gas separation, pervaporation, membrane distillation, etc. [9]. Proof of several membrane processes for separating boron from water has been demonstrated. For example, reverse osmosis (RO), forward osmosis (FO), nanofiltration (NF), ultrafiltration (UF) and membrane distillation (MD). In view of the booming trend in the application of deboronation membranes, an overview of the development of membrane technology in the past is needed. Therefore, this review aims to provide a comprehensive overview of the latest advances in membrane technology research and development from the perspective of membrane materials, membrane manufacturing and system design. We believe that the information provided will provide useful insights into the design of boron-depleting materials and process designs in a variety of aqueous systems.

 

2. Boron in the environment

Boron, which is a ubiquitous element in nature, is widely distributed in (1) lithosphere, as borate minerals (such as Na2B4O7·10H2O, etc.) and (2) as various water bodies mainly in the form of boric acid. The average boron content in the earth's crust is 1 to 500 mg kg-1, while the average boron content in the soil is 2 to 100 mg kg-1 [1]. In contrast, the main source of boron is the concentration of boron in the ocean ranging from 0.5 to 9.6 mg L-1 [10]. The boron content in uncontaminated surface water and groundwater is usually less than 0.5 ppm. However, due to human activities, it has been found to increase significantly in recent years [10-12]. Due to the emission of boron waste, the concentration of boron in surface water can be as high as 100 ppm. For example, the background boron concentration in a river in Liaoning Province, China is less than 0.5 ppm, while the boron concentration in surface water and groundwater in the polluted river section is 23.1 and 495.6 times, respectively, in the background area. [13]. This may be due to mining operations nearby. The potential for environmental and health problems has caused great concern around the world.

 

3. The toxicity of boron

Although trace elements are unavoidable, boron may be toxic to living things. In particular, plants are particularly sensitive to boron concentrations. For example, to maintain good wheat growth, it should be kept between 0.75 and 1.0 ppm in soil water [14]. Higher boron doses may slowly develop toxic symptoms. Physiological chlorophyll, inhibition of photosynthesis, deposition of lignin and cork, increased membrane leakage, lipid peroxidation and changes in antioxidant pathways [3]. It should be noted that the toxicity of boron is a function of its concentration in soil water and exposure time. On the other hand, the adverse effects of boron on animals and humans have been demonstrated in laboratory animals. Long-term consumption of water and food contaminated with boron may cause cardiovascular, neurological and digestive diseases and diseases [2]. Ku et al also reported. Short-term and long-term oral administration of boric acid or borax may have a negative impact on the male reproductive tract of rats [4]. Therefore, it is very important to control the boron content in the water source and produce low boron content water for various uses. Drinking water and irrigation.