Currently, amidst changing environmental conditions and the emergence of various public health crises, consumers are placing greater emphasis on household hygiene and health. Concurrently, functionalization has emerged as a key developmental trend in the household detergent sector; consumers are no longer satisfied with detergents that merely offer standard cleaning capabilities, but also seek additional attributes such as sterilization and fragrance. Furthermore, the widespread adoption of fully automatic washing machines has led consumers to increasingly prefer washing various types of clothing in combined loads. These factors have driven a rapid surge in consumer demand for household detergent products with disinfecting and sanitizing properties.
In recent years, the variety of sanitizing and disinfecting products has also expanded significantly, evolving from single-purpose disinfectants into multi-functional compound products that combine both cleaning and sterilizing capabilities. Moreover, the scope of application has broadened from textiles alone to encompass a wide array of household cleaning products-such as dishwashing detergents, floor and surface cleaners, and toilet bowl cleaners.
According to the relevant provisions of standard QB/T 2850-2007, *Antibacterial and Bacteriostatic Detergents*, the products referred to as "antibacterial and bacteriostatic detergents" within this industry are formulated using surfactants in combination with specific bactericides or bacteriostats; these are daily-use chemical cleaning products that possess both antibacterial/bacteriostatic properties and cleaning/stain-removal functions. The formulation of such sanitizing and disinfecting detergents presents several technical challenges: First, selecting appropriate bactericides; second, evaluating the compatibility and synergistic performance of the selected bactericides when combined with other detergent components; and third, determining the optimal method for incorporating the bactericides into the formulation. This paper focuses on these three aspects, systematically reviewing the ingredients responsible for providing sterilizing and bacteriostatic effects in household detergents-specifically examining their compatibility characteristics and methods of incorporation.
1. Types of Bactericides in Household Detergents
Based on their origin, bactericides can be broadly classified into synthetic bactericides and natural bactericides. Based on their chemical composition, they can be categorized into halogen-based, oxygen-based, aldehyde-based, phenol-based, quaternary ammonium salts, guanidine-based compounds, traditional herbal extracts, and other types. In the context of daily-use chemical detergents, the primary target microorganisms for these bactericides are *Staphylococcus aureus*, *Escherichia coli* (E. coli), and *Candida albicans*. Bactericides used in household detergents should meet the following criteria: ① High safety-non-toxic to humans and low in irritancy; ② High efficiency-effective even when added in small quantities; ③ Good compatibility with surfactants and other detergent auxiliaries; ④ Good solubility and dispersibility-without compromising the product's fundamental performance or fragrance.
Halogen-based Agents
Halogen-based bactericides include chlorine-containing, bromine-containing, and iodine-containing agents. Since halogen elements inherently possess strong oxidizing properties, compounds containing these elements typically exhibit potent bactericidal and bleaching capabilities.
① Chlorine-containing Bactericides
Chlorine-containing bactericides possess strong bactericidal power, capable of eliminating various microorganisms-including bacterial spores. Furthermore, they offer advantages such as wide availability and low cost; however, their strong irritancy and sensitivity to pH limit their scope of application. Common chlorine-containing bactericides used in household detergents primarily include sodium hypochlorite and sodium dichloroisocyanurate. Industrially produced sodium hypochlorite typically contains an active chlorine content of approximately 10% to 20%; it acts as a strong oxidizing agent with potent bactericidal and bleaching effects, though it is corrosive to metals and prone to decomposition. In terms of compatibility, sodium hypochlorite can damage certain dyes and reacts adversely with fragrances, enzymes, and fluorescent whitening agents; consequently, it is often utilized independently in disinfectant solutions and bleach products. Sodium dichloroisocyanurate-also known as Dichlor-is a broad-spectrum bactericide; while its dry powder form is stable during storage, its aqueous solution exhibits poor stability. Sodium dichloroisocyanurate presents no cumulative toxicity or mutagenic effects, offers a high safety profile, and is therefore suitable for use in household detergents. In terms of compatibility, substances such as fatty acid diethanolamides, alkylphenol polyoxyethylene ethers, borax, and soda ash exert a decomposition effect on sodium dichloroisocyanurate; conversely, substances such as sodium alkylbenzenesulfonate, sodium fatty alcohol ether sulfate, fatty alcohol polyoxyethylene ethers, sodium sulfate, and sodium chloride enhance the stability of sodium dichloroisocyanurate.
② Bromine-based Bactericides
Common varieties of bromine-based bactericides primarily include bromochlorodimethylhydantoin and dibromodimethylhydantoin; these agents are environmentally friendly following use. Compared to chlorine-based bactericides, bromine-based agents exhibit superior microbial killing efficacy in alkaline environments and degrade more rapidly. However, due to their higher cost, bromine-based bactericides are predominantly utilized for disinfection in hospitals and epidemic-stricken areas, while their application in household detergents remains relatively limited.
③ Iodine-based Bactericides
Iodine-based bactericides-such as elemental iodine and iodophors-are widely employed in the fields of medicine and public health; in recent years, they have also found application within the detergent industry. Elemental iodine possesses excellent permeability, enabling it to rapidly penetrate cell walls and induce the denaturation and inactivation of proteins. Studies have demonstrated that by formulating a blend of 0.5% iodine with twelve different surfactants-including sodium fatty alcohol polyoxyethylene ether sulfate (AES)-the resulting iodine-based antimicrobial detergent achieves highly satisfactory levels of both detergency and bactericidal efficacy.
Peroxides
Upon dissolution in water, peroxide-based bactericides dissociate to generate free radicals possessing high redox potentials. These radicals subsequently disrupt the permeability barriers of microorganisms-or attack their proteins, DNA, and other cellular components-ultimately leading to microbial death.
① Liquid Peroxides
The primary liquid peroxides utilized in this context are hydrogen peroxide and peracetic acid. These substances are highly corrosive in nature and exert a bleaching effect on fabrics. Currently, hydrogen peroxide is primarily utilized in the formulations of color-safe bleaches. While some research has explored its application in dishwashing detergents, its incorporation into such formulations presents numerous compatibility challenges, as its decomposition can be triggered by factors such as heavy metals, alkaline environments, and exposure to light.
② Solid Peroxides
Solid peroxides-specifically sodium perborate and sodium percarbonate-are predominantly employed in powdered detergent formulations. Notably, both sodium perborate and sodium percarbonate require elevated temperatures to release oxygen; consequently, they do not exert their bactericidal efficacy until the temperature exceeds 40°C. Furthermore, the stability of compounds such as sodium percarbonate is relatively poor. Based on these characteristics, this class of biocides is primarily utilized in formulations for washing machine tub cleaners, drain openers, and similar products.
③ Stabilized Chlorine Dioxide
Chlorine dioxide is classified by the World Health Organization as a Class A1 highly effective and safe biocide. At room temperature, it exists as a yellowish-green gas characterized by high chemical reactivity, and its disinfecting efficacy is five times greater than that of elemental chlorine.
Guanidine Derivatives
Guanidine-based biocides are broadly categorized into biguanides and monoguanides. The biguanide category includes chlorhexidine and its derivatives, polyhexamethylene biguanide salts, and polyaminopropyl biguanide, among others. The monoguanide category consists primarily of polyhexamethylene monoguanide, available in various salt forms such as the hydrochloride, stearate, and propionate. Studies have indicated that the hydrochloride form exhibits stronger bactericidal efficacy compared to other salt forms.
Chlorhexidine (also known as Hibitane) is predominantly available in two forms: the acetate and the gluconate. It possesses broad-spectrum bacteriostatic properties; at high concentrations, it demonstrates both bactericidal and bacteriostatic effects, whereas at low concentrations, its action is primarily bacteriostatic. However, chlorhexidine is ineffective against bacterial spores and fungi. In the field of daily chemical products, it is commonly utilized as a preservative in hand sanitizers, toothpastes, and skincare products.
Polyhexamethylene guanidine hydrochloride is classified as a low-toxicity substance; it is non-corrosive to metals and does not exert a bleaching effect on fabrics. This class of biocides exhibits excellent water solubility and thermal stability; they produce minimal foam, are easy to rinse off, and are insensitive to pH fluctuations. Compared to chlorine-based or peroxide-based biocides, polyhexamethylene guanidine (PHMG) biocides possess lower toxicity and irritancy, making them safer for use; consequently, they are widely incorporated into household detergents. Studies have demonstrated that the application of PHMG biocides for a contact time of just 5 to 10 minutes is sufficient to reduce the total bacterial count and coliform levels on tableware surfaces to levels compliant with relevant national hygiene standards. Major detergent manufacturers have subsequently launched a diverse range of household cleaning products featuring PHMG as the active biocide ingredient. Regarding compatibility, since guanidine-based biocides are cationic agents, their use should be avoided in conjunction with soaps, anionic surfactants, and similar substances; furthermore, certain non-ionic surfactants may also compromise their biocidal efficacy. Additionally, PHMG used as a standalone ingredient in a formulation is classified as a low-efficiency biocide; therefore, in applications requiring high-intensity or prolonged disinfection effects, it should be utilized synergistically with other biocidal agents.
Quaternary Ammonium Salts
Quaternary ammonium salts are a class of cationic surfactants. Among them, alkyl-based quaternary ammonium salts-specifically categorized into single-chain and double-chain variants-are the most widely employed as biocides. To date, this class has evolved through seven generations of products. The first and second generations are typified by benzalkonium chloride and benzalkonium bromide, while the seventh generation consists of mixtures comprising polymeric quaternary ammonium salts combined with alkyl dimethyl benzyl ammonium chloride and alkyl dimethyl ethyl benzyl ammonium chloride. Although quaternary ammonium salts are ineffective against fungi, *Mycobacterium tuberculosis*, and bacterial spores, they possess potent bacteriostatic properties, capable of inhibiting bacterial growth and reproduction even at extremely low concentrations.
In terms of compatibility, all quaternary ammonium biocides function as cationic surfactants. While double-chain quaternary ammonium salts demonstrate a certain degree of resistance to the adverse effects of anionic surfactants and hard water, their co-formulation or simultaneous use with anionic surfactants should nevertheless be avoided. Furthermore, substances such as iodine, potassium iodide, salicylic acid, and peroxides exhibit antagonistic effects when combined with quaternary ammonium disinfectants; therefore, the admixture of these substances should be avoided during application. In recent years, the use of quaternary ammonium disinfectants in household detergents has become increasingly widespread.
Other Synthetic Disinfectants
Synthetic disinfectants also encompass categories such as aldehydes and phenols. Among aldehyde-based disinfectants, formaldehyde is highly irritating, acts slowly, and poses potential carcinogenic risks. Regarding phenol-based disinfectants, the potential hazards associated with commonly used agents-such as triclosan and triclocarban-are being continuously exposed; given these safety concerns, their inclusion in product formulations requires careful and prudent consideration.
Natural Disinfectants
Based on their origin, natural disinfectants can be broadly classified into plant-derived, animal-derived, and microorganism-derived categories. Due to their low toxicity and minimal irritancy, natural disinfectants tend to be more readily accepted by consumers, leading to a continuous surge in research interest within this field. Current research efforts focus primarily on plant-derived disinfectants, although a limited number of studies have also explored the incorporation of animal- or microorganism-derived disinfectants into household detergent formulations.
① Plant-Derived Disinfectants
Plant-derived disinfectants are defined as antimicrobial preparations produced by extracting components-possessing bactericidal or bacteriostatic activity-from various plant parts, such as roots, stems, leaves, and flowers, for use against pathogenic microorganisms. The primary active constituents found in plant-derived disinfectants include alkaloids, flavonoids, steroids, terpenes, tannins, essential oils, terpenoids, saponins, coumarins, lignans, stilbenes, polysaccharides, phenols, quinones, esters, and organic acids. When incorporating plant-derived disinfectants into detergent formulations, two primary challenges arise: first, determining the optimal dosage; and second, managing the resulting color of the detergent system. Although plant-derived disinfectants generally possess limited antimicrobial potency and entail higher production costs, their low irritancy profile has led to their increasingly widespread application in household detergent products.
② Animal-Derived Biocides
Substances extracted from animals-such as lysozyme, antimicrobial peptides, and antimicrobial proteins-all possess varying degrees of antimicrobial efficacy. Currently, chitosan is the most widely utilized animal-derived agent in the detergent sector; however, its application in detergents is significantly constrained by its poor solubility in water and most organic solvents, as well as its inherently mild antimicrobial potency. To address these limitations, research efforts have focused on enhancing chitosan's antimicrobial capabilities through chemical modification to develop a series of chitosan derivatives, or by incorporating highly potent antimicrobial factors into the chitosan matrix.
③ Microbe-Derived Biocides
Microbe-derived biocides can be broadly categorized into two types: the first involves the direct application of microorganisms-such as bacteriophages, viruses, bacteria, and fungi-to achieve antimicrobial effects; the second utilizes the metabolic byproducts of microorganisms for antimicrobial purposes. To date, research regarding the application of this specific class of biocides in detergent formulations remains relatively limited.
Selection and Incorporation of Biocides in Household Detergents
The formulation design of antimicrobial detergents requires careful consideration of the specific characteristics of the surfaces or objects being cleaned. This entails selecting appropriate biocides and surfactants, as well as evaluating the synergistic compatibility of the various components within the blend. Taking floor and furniture cleaners as an example: chlorine-based biocides are generally avoided because they cause discoloration in wood; cationic quaternary ammonium salts are relatively mild and possess low toxicity, though their antimicrobial efficacy is comparatively weaker; polyhexamethylene biguanide (PHMB), conversely, is effective against both Gram-positive and Gram-negative bacteria. Furthermore, it is non-toxic, non-irritating, and effective against fungi and molds-such as *Candida albicans*. Due to its polymeric molecular structure, PHMB adsorbs onto floor and furniture surfaces after repeated use, thereby providing a sustained antimicrobial effect. Based on these comprehensive considerations, the selected formulation employs a blended biocide system comprising 20% polyhexamethylene biguanide quaternary ammonium salt, 45% dodecyl dimethyl benzyl ammonium chloride, and a dialkyl quaternary ammonium salt for use in floor and furniture cleaning products. Given the selection of cationic biocides, particular care must be exercised when choosing the surfactants to be blended with them to ensure compatibility and optimal performance. Ultimately, the formulation utilizes fatty alcohol polyoxyethylene ethers, dodecyl dimethyl betaine, branched-chain fatty alcohol polyoxyethylene ethers, alkyl glucosides, and amine oxides as the primary surfactant components. Specifically, fatty alcohol polyoxyethylene ethers significantly reduce surface tension, thereby facilitating the migration of biocides to bacterial cell surfaces and their subsequent penetration into the cell interior, thereby enhancing their bactericidal efficacy. Dodecyl dimethyl betaine and amine oxides possess inherent bactericidal properties and exhibit a synergistic effect with regard to detergency. Alkyl glucosides are mild in nature and possess excellent spreading capabilities, effectively reducing the tacky sensation left on the surfaces of floors and furniture.
Regarding the method of biocide incorporation, most biocides are added directly to detergent formulations as raw materials during the compounding process. While this approach is simple and easy to execute, it provides antimicrobial or bacteriostatic benefits to the cleaned object only during the actual washing cycle; it offers limited retention of these benefits once the cleaning process is complete. This limitation is particularly pronounced in products such as laundry detergents, which require extensive rinsing with large volumes of water during the final stages of the wash cycle, making the sustained maintenance of antimicrobial or bacteriostatic benefits even more challenging. Consequently, some research efforts have focused on developing alternative incorporation methods-such as the use of microencapsulation-to achieve sustained-release properties for these beneficial agents.
