## 1 Introduction  
In recent years, shortages of resources and energy are key issues that become more and more significant and have to be confronted in many countries. The development and utilization of biomass resource is known as an effective means to address this issue due to its unique characteristics such as high abundance, superior renewablilty, and remarkable sustainability [1]. In fact, effective transmission of biomass to value-added chemicals and high energy-density fuels has received considerable attention, which is pivotal for a more sustainable economy and carbon-neutral society [2]. Biomass is a promising renewable energy that can be derived from various sustainable sources, including lignocellulosic, lipids, starch, and aquatic plants. Among various biomass resources, corncob is highly valued since it contains large amounts of pentosans and hexoses. In fact, corncob is an important raw material for producing pentose [3], hydroxymethylfurfural [4], ethanol [5], xylitolp [6], levulinic acid [7], formic acid and acetic acid [8], etc. These products are highly applicable in various fields including food, medicine [9; 10], and fine chemicals [11; 12]. However, due to production costs and technical restrictions, large majority of corncobs are still incinerated, giving rise to huge waste of resources and severe environmental problems. For biomass transmission, pretreatment is the most critical processing step, influencing downstream processes [13] such as conditioning of pretreated samples, recovery of coproducts, and wastewater treatment [14]. More importantly, an appropriate pretreatment setp is essential to improve the conversion rate of biomass resources to value-added chemicals and to reduce difficulties on subsequent separation and purification of the final products. Depending on different target products, biomass pretreatment approaches can be various [15]. To date, techniques on effective pretreatment of biomass are well developed, including steam explosion method [16; 17], alkali treatment [18; 19], supercritical water gasification [20], microbial treatment [21], acid treatment [22], etc. For example, [PERSON] et al. [14] proposed a two-setp com stover pretreatment method, i.e., hot water pretreatment followed by disk milling, to achieve high sugar yields with low inhibitor concentrations. [PERSON] et al. [18] adopted the mild alkali for rice straw pretreatment. By removing the majority of the lignins while increasing the content of cellulose, the efficiency of enzymatic hydrolysis at high-solid loadings for fermentable sugar production are improved. Among various pretreatment methods, acid treatment has been widely utilized for corncob pretreatment, especially in industrial production due to its technically mature. During the acid pretreatment process, dilute sulfuric acid and/or nitric acid are usually adopted since they are low-cost and readily available chemicals for industrial applications. It is known that corncob is lignocellulosic material that has a basic composition of cellulose (40-44%), hemicellulose (31-33%), and lignin (16-18%) [23]. In addition to the basic composition, other substances such as salts, proteins, starch and ashes occupy a small portion (less than 10% in total) of the corncob [24]. Depending on where the corncob originates, the proportions of cellulose, hemicellulose, lignin, and other substances in corncobs vary modesty. [PERSON] et al. [25] used dilute nitric acid for corncobs pretreatment, aiming at converting hemicellulose from corncob to fermentable sugars for bio-methane and bio-ethanol production. Based on the optimized conditions, corncobs were processed with nitric acid concentration of 2.0 vol.% at 121 \({}^{\circ}\)C and a 1:5 solid-to-liquid ratio, yielding sugar concentration as high as 110.12 mg\(\cdot\)mL\({}^{-1}\). As an alternative, dilute sulfuric acid was also used as pretreatment solution in [PERSON]'s work. By comparison, both acids yield almost the same sugar concentrations at identical operation conditions.