Antiscalant and Dispersant

Introduction

Antiscalants and dispersants are a family of chemicals designed to inhibit the formation and precipitation of scales and to inhibit the agglomeration and deposition of foulants. In industrial production, most water systems (such as reverse osmosis, circulating cooling water, seawater desalination plants, oilfield development, boiler water, etc.) contain a large number of scaling ions such as Ca²⁺, Mg²⁺, Fe²⁺, HCO₃-, SO₄^2-, etc.). With the continuous operation of each water system, the concentration of these scaling ions will continue to increase, resulting in the scale formation (such as CaCO₃, CaSO₄, BaSO₄, SrSO₄, etc.) and pollutant deposition on the pipe wall of water system. This will make the system pipe clogging, thus reducing the heat transfer efficiency, increasing energy consumption, and then bring huge economic losses to enterprises. Adding antiscalant and dispersant to water is the most widely used treatment method, which can fundamentally inhibit the scales formation and prevent the deposition of foulants, and possesses the advantages of simple, effective and low cost.

Fig. 1. The scale deposition on the pipe.

Classification

Antiscalant and dispersant can be divided into two categories of natural antiscalant and dispersant and synthetic antiscalant and dispersant, and the synthetic antiscalant and dispersant can be divided into many kinds.

Natural antiscalant and dispersant: Natural macromolecules such as starch, tannin and lignin can chelate scale ions and inhibit the formation of scale due to their structure containing many functional groups of hydroxyl, phenolic hydroxyl and carboxyl. Thus they have been used as antiscalant and dispersant in the early years. However, they suffer the disadvantages of poor temperature resistance, unstable physical and chemical properties, and low scale inhibition performance. So, they have rarely been used in industry at present.

Synthetic antiscalant and dispersant: The synthetic antiscalant and dispersant can be mainly divided into five categories of organophosphorus antiscalant and dispersant , polycarboxylic antiscalant and dispersant, sulfonic acid polymer antiscalant and dispersant , polyether antiscalant and dispersant , eco-friendly antiscalant and dispersant.

• Organophosphorus antiscalant and dispersant: The water treatment agent usually contains one or more phosphonic acid groups in its structure and has excellent scale inhibition, stable properties and good temperature resistance. Common commercial organophosphorus antiscalants and dispersants include amino trimethylphosphonic acid (ATMP), hydroxyethyl diphosphonic acid (HEDP), phosphonobutane tricarboxylic acid (PBTC), polyamino polyether tetramethylphosphonic acid (PAPEMP), ethylenediamine tetramethylphosphonic acid (EDTMP), etc.

Fig. 2. The structure of ATMP.

• Polycarboxylic antiscalant and dispersant: The water treatment agent is an organic polymer material that polymerized by the monomer containing carboxylic acid group, which has the good inhibition effect of CaCO3 and CaSO4. Hydrolyzed polymaleic anhydride (HPMA) and polyacrylic acid (PAA) are the most common polycarboxylic antiscalant and dispersant.

Fig. 3. The structure of HPMA.

• Sulfonic acid polymer antiscalant and dispersant: The water treatment agent is formed by polymerization of monomers containing sulfonic acid groups, which has good dispersion performance because of sulfonic acid group with strong acidity. At present, most sulfonic acid polymer antiscalants and dispersants are developed based on the monomer of 2-acrylamide-2-methylpropyl sulfonic acid (AMPS).
• Polyether antiscalant and dispersant: The water treatment agent is a relatively new type of polymer antiscalant and dispersant, which polymerized by the double bond monomers containing ether bond (such as polyoxyethylene ether) with other monomers. The ether bond with excellent hydrophilicity can improve the dispersion ability and Ca²⁺ tolerance, thus improving the performance of the polymer. In addition, ether bond can be degraded into CO₂ and H₂O under anaerobic and aerobic conditions that is conducive to the environmental protection. Therefore, in recent years, the polyether antiscalant and dispersant has also been continuously developed.
• Eco-friendly antiscalant and dispersant: Due to the continuous deterioration of the environment and more strict environmental protection policies, water treatment agents have tended to green. Polyaspartic acid (PASP) and polyepoxysuccinic acid (PESA) are the two representatives of environmentally-friendly antiscalants and dispersants. Thereinto, PASP has good scale inhibition performance, dispersion effect, biocompatibility and thermal stability. Therefore, it has been hailed as the most promising scale inhibitor at present.

Fig. 4. The structure of PASP.

Alfa Chemistry can offer various antiscalants and dispersants such as polycarboxylic antiscalant and dispersant, organophosphonic antiscalant and dispersant, eco-friendly antiscalant and dispersant, composite antiscalant and dispersant and many others. If you have any needs, please contact us.