water Article Biochar from Agricultural by-Products for the Removal of Lead and Cadmium from Drinking Water Edgar Pineda Puglla 1 , Diana Guaya 2 , Cristhian Tituana 3 , Francisco Osorio 4 and María J. García-Ruiz 4, * 1 Department of Geology, Mines and Civil Engineering, UTPL, Universidad Técnica Particular de Loja, Barrio San Cayetano Alto, Marcelino Champagnat Street, s/n, Loja 110107, Ecuador; eipineda@utpl.edu.ec 2 Department of Chemical, UTPL, Universidad Técnica Particular de Loja, Barrio San Cayetano Alto, Marcelino Champagnat Street, s/n, Loja 110107, Ecuador; deguaya@utpl.edu.ec 3 Civil Engineering Degree, UTPL, Universidad Técnica Particular de Loja, Barrio San Cayetano Alto, Marcelino Champagnat Street, s/n, Loja 110107, Ecuador; catituana1@utpl.edu.ec 4 Department of Civil Engineering, Institute of Water, University of Granada, Ramón y Cajal Street, 4, 18071 Granada, Spain; fosorio@ugr.es * Correspondence: mjgruiz@ugr.es; Tel.: +34-9-5824-9463 Received: 29 August 2020; Accepted: 14 October 2020; Published: 20 October 2020   Abstract: This study reports the adsorption capacity of lead Pb 2+ and cadmium Cd 2+ of biochar obtained from: peanut shell (BCM), “chonta” pulp (BCH) and corn cob (BZM) calcined at 500, 600 and 700 ◦ C, respectively. The optimal adsorbent dose, pH, maximum adsorption capacity and adsorption kinetics were evaluated. The biochar with the highest Pb 2+ and Cd 2+ removal capacity is obtained from the peanut shell (BCM) calcined at 565 ◦ C in 45 min. The optimal experimental conditions were: 14 g L −1 (dose of sorbent) and pH between 5 and 7. The sorption experimental data were best fitted to the Freundlich isotherm model. High removal rates were obtained: 95.96% for Pb 2+ and 99.05. for Cd 2+ . The BCH and BZM revealed lower efficiency of Pb 2+ and Cd 2+ removal than BCM biochar. The results suggest that biochar may be useful for the removal of heavy metals (Pb 2+ and Cd 2+ ) from drinking water. Keywords: peanut shell; “chonta” pulp; corn cob; biochar; adsorption; lead; cadmium; drinking water 1. Introduction Water pollution by wastewater discharges into rivers or bodies of water by anthropogenic activities has increased due to population growth [1,2]. Heavy metals in water promote toxicity, and they are not biodegradable [3,4]. Low concentration of heavy metals has a great impact on human health and aquatic life. They can cause respiratory problems, weakening of the immune system, damage to the kidneys or liver, genetic and neurological alterations and death [5]. Lead (Pb 2+ ) and cadmium (Cd 2+ ) are abundant in nature; however, they are very toxic. Pb 2+ and Cd 2+ are incorporated into the food chain in low concentrations by water systems, affecting wildlife and people [6]. In South America, some rivers that supply drinking water to cities contain Pb 2+ in high concentrations. The Rímac River in Lima, Peru, in 2009, registered a concentration of 2.15 mg L −1 Pb 2+ [7]. In 2017, the Rímac river maintained a high Pb 2+ concentration (2.064 mg L −1 ) and also reported a Cd 2+ concentration of 0.038 mg L −1 [8]. In Ecuador, some rivers contain heavy metals from mining [9]. The Puyango river, located between Loja and El Oro provinces at southern Ecuador, reported an average content of 0.77 mg L −1 of Pb 2+ . However, the water from Puyango river is used for agricultural application and human consumption by northern Peru. Water 2020, 12, 2933; doi:10.3390/w12102933 www.mdpi.com/journal/water