Removal of heavy metals using food industry waste as a cheap adsorbent

Due to the high capacity of food factories, a lot of waste is generated. Due to the presence of nutrients in them can increase pollution in the sewerage network and cause environmental problems. To animal feed, grain waste can be used to produce fertilizer, compost, fuel, soil cover, etc. The natural pigment lycopene, thickeners, proteins, etc., can be produced from the seeds and skin of the tomato paste factory waste. In the present paper, soybean oil residue was used to remove cadmium, zinc, and lead ions from aqueous solutions. Discontinuous experiments to investigate the effect of initial concentration (100-300 ppm), solution pH (1-5), contact time (1-60 min), adsorbent amount (0.02-2 g) on the uptake of cadmium, zinc, and lead ions by soybean oil residues. The results showed that with increasing the pH, the value of the contact time, the amount of adsorbent, and the adsorption rate increases with increasing the initial concentration of metal ions, the adsorption rate decreases. According to the results, the best pH for adsorption of metal ions is about 3-5, and the equilibrium time for cadmium ions is 40 minutes, for zinc ions is 20 minutes, and for lead, the ion is 10 minutes.