## 1 Introduction  
The water purifying agent polyaluminum chloride occupies a dominant position in the market of drinking water coagulants [1]. According to relevant statistics, in 2015, there were more than 300 water purification agent enterprises in China, and the market demand for water purification agents was 4.176 million tons. Each ton of polyaluminum chloride will produce 15 wt% of polyaluminum chloride slag, and the annual production of wet-based polyaluminum chloride slag will reach more than one million tons [2]. Chlorine salt contained in polyaluminum chloride slag brings some difficulties to the treatment process. At present, the commonly used disposal methods of polyaluminum chloride slag are landfill and discarding, which not only pollutes the environment, but also wastes land resources. Recycling is an ideal solution for solid waste residue. In order to solve the resource utilization of polyaluminum chloride slag, various researchers use harmless polyaluminum chloride slag to produce cement, filler, adsorbent, clay, concrete and other products, but the utilization rate of these products is low and the consumption is small [3; 4; 5; 6; 7]. The main components of polyaluminum chloride slag are SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\), which are similar to those of clay and have the conditions for preparing sintered bricks.  
With the prohibition of sintered clay bricks, the preparation of sintered bricks from industrial solid wastes is an effective way to solve the problem of bulk solid wastes. The use of industrial solid wastes, such as coal gangue, agro-industrial wastes, alkaline-activated slag, fly ash and pyrite cinder, instead of clay to prepare building materials conforms to the sustainable development method [8; 9; 10; 11; 12; 13; 14].  
[PERSON] showed that by using pyrrhotite and yellow clay to burn sintered bricks at 1000 \({}^{\circ}\)C, the utilization rate of pyrrhotite can reach 30% [15]. Fly ash is used to replace clay to prepare sintered bricks. The highly doped fly ash sintered bricks have higher compressive strength and lower water absorption [16]. Adding solid waste to clay bricks can also improve the properties of fired bricks, such as light weight, good thermal insulation and high strength [17; 18; 19; 20; 21]. Glass powder is a commonly used additive in the preparation of sintered bricks [22; 23]. Adding glass powder as a flux can reduce the sintering temperature of sintered bricks, improve the compressive strength of sintered bricks and reduce the water absorption and linear shrinkage [24; 25]. Research by [PERSON] shows that adding glass powder to sintered clay bricks can reduce the sintering temperature to 650 \({}^{\circ}\)C and improve the compressive strength of sintered bricks [26]. A series of studies have been carried out on the application of glass powder to sintered bricks, but few reports have been made on the preparation of sintered bricks using polyaluminum chloride slag and glass powder.  
In this study, firstly, quicklime was used to neutralize polyaluminum chloride slag. Then, fired brick was prepared by adding glass powder to polyaluminum chloride slag. The effects of the glass powder content, molding moisture, molding pressure, heating mode, heating rate and sintering temperature on the properties (compressive strength, water absorption, bulk density and linear shrinkage) of fired brick were systematically studied. After obtaining the best technological parameters for preparing sintered bricks, XRD and SEM analysis were carried out for sintered bricks at different temperatures. The research results provide a reference for the preparation of sintered bricks from polyaluminum chloride slag.