Chapter 4 - Summary of research on biochar adsorption of chemical pollutants
Introduction
The author attaching a thermocouple probe and temperature datalogger to a prototype gasifier drum kiln for making biochar adsorbent, Pun Pun Farm, Thailand, winter 2011/2012. (Photo credit Lyse Kong.)
Introduction
This Chapter is a digest of key articles from the peer-reviewed literature on biochar adsorption – the scientific source-material that provides the foundation for using biochar in water treatment applications. The purpose of this Chapter is to provide an English-to-English translation from the jargon-y academicspeak of journal publications to a user-oriented dialect and format, accessible to practitioners as well as to non-specialists.
The Chapter has five main sections:
The Char…From an adsorption perspective, not all biochars are created equal. This section investigates biochars made from a variety of biomass precursors (feedstocks) using different pyrolysis systems. The objective is to hone in on optimal techniques for generating effective adsorbents, including low-cost methods for achieving pseudo-activation conditions. This section interrogates a bevy of batch test data quantifying adsorption of several of our sentinel chemicals in comparison with activated carbon benchmarks.
The Water…As elaborated in Chapter 3, water quality parameters such as pH and the concentration and character of background dissolved organic matter (DOM) play profound roles affecting the uptake of target pollutants by adsorbents. This section provides quantitative insight into how source water characteristics influence biochar water treatment system performance.
The Contactor…There are, primarily, two modes of contact used for adsorption processes in water treatment: batch (continuously-stirred tank reactor, CSTR) mode, and column (fixed-bed) mode. As detailed in Chapter 3, the dynamics of mass transfer of pollutant molecules from bulk solution to interior pore surfaces differ between these two modes, especially in the presence of DOM. This section builds on the batch test datasets examined in the previous two sections and expands it with a raft of column test data. It ends with recommendations for how to use lab bench-scale column experiments to model the treatment performance of full-sized systems.
Surrogate monitoring…Quantifying individual pollutants of concern at trace (ng/L to mg/L) levels is expensive and requires sophisticated laboratory instrumentation and highly specialized data analysis. Accordingly, it’s usually cost-prohibitive and logistically infeasible to perform direct monitoring in remote and low-resource settings. This section summarizes cutting-edge research on the use of surrogate methods for monitoring the performance of biochar water treatment systems that can be measured inexpensively in the field or in a field-lab setting by local water quality technicians with a little training.
Summary and BWT design specifications… The Chapter culminates in an overview of how biochar water treatment system design, operation, and monitoring guidelines are derived from datasets quantifying removal of sentinel chemicals and field surrogates from model waters.
Let’s begin…