Pyrolysis of chromed leather waste with CaO obtained from waste marble to prevent environmental pollution

Waste management and production of value-added chemicals were carried out by pyrolysis of chromium leather waste using CaO obtained from marble waste. The CaO was characterized by XRD, SEM, TGA, and BET techniques, and the analysis of pyrolysis experiment products in the presence/absence of CaO were characterized/detected by FT-IR, elemental, GC–MS, and micro-GC–MS, and calorific value analysis. The effects of pyrolysis temperature, N₂ flow rate, heating rate, retention time and CaO amount on the yield of the obtained liquid product (bio-oil) were investigated. In addition, the effect of the catalyst on the gas product composition was also determined. The highest liquid product yield were obtained without CaO 35.5% and with CaO 49% in the pyrolysis temperature 500 ºC, nitrogen gas flow rate 0.50 L·min⁻¹, heating rate 50° L·min⁻¹, and retention time 20 min. Moreover, the deoxygenation during pyrolysis increased the C/O ratio in the liquid product composition and, consequently, the calorific value (up to 13%). In addition, while the amount of CO₂ among the gaseous products formed during pyrolysis decreased from 38 to 1% due to capture by the CaO, the increase in the amounts of H₂ and acetylene was approximately two-fold and 30-fold, respectively. So, the pyrolysis of leather/marble waste is a viable process that can enhance the quality of pyrolysis products, and prevent possible environmental pollution.